Endocrino Flashcards
How to interpret ACTH dosage tests in PPID ?
The combination of clinical signs and age informs the index of clinical suspicion prior to diagnostic testing.
Both pre-test probability of disease and season of testing have strong influence on the ability to diagnose PPID using basal ACTH or ACTH after TRH stimulation.
Thus, it should be remembered that the risk of an FP result increases in situations where there is a low pre-test probability.
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
Does plasma ACTH dosage (basal and TRH-stimulation test) rather sensitive or specific?
The specificity of the test outweighs its sensitivity, indicating that low concentrations are more useful to rule out the disease than are high concentrations to confirm the disease.
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
What is the effect of breed on plasma ACTH in equids ?
Breed differences in basal ACTH concentrations have been reported. Some pony breeds, donkeys, and Arabians have higher basal ACTH concentrations than horses, particularly in autumn.
Breed and time of year should be considered when interpreting plasma ACTH concentrations in equids suspected for PPID.
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
Which breeds are predisposed to PPID ?
There is no evidence supporting a breed predisposition to PPID. Breed or type is of limited use for estimating pre-test probability.
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
What is the effect of age on plasma ACTH in equids ?
Association between increasing horse age and increased ACTH concentrations in healthy horses and ponies.
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
What is the prevalence of PPID in horses ?
The prevalence of PPID in equids aged ≥15 years is between 21% and 27%.
Odds of PPID increases by 18% in horses/ponies for every year > 15 years of age
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
What are the clinical signs associated with high clinical suspicion of PPID ?
- Generalised or regional hypertrichosis
- Delayed / incomplete hair coat shedding
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
What are the clinical signs associated with moderate clinical suspicion of PPID ?
- Hyperhydrosis
- Abnormal fat distribution / regional adiposity
- Epiaxial muscle atrophy
- Laminitis
- Weight loss
- Recurrent opportunistic infections
- Behavioural changes / docility / lethargy
- PUPD
- Pot-bellied appearance
- Bulging supra-orbital fat
- Lordosis
- Infertility
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
What is the effect of geographical location on plasma ACTH in equids ?
Significant effect of latitude on ACTH concentration has been reported in both northern and southern hemispheres, reflecting differences in photoperiod.
Latitude-specific reference intervals are required when interpreting ACTH concentrations for PPID diagnosis.
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
What factors influence ACTH concentration in healthy horses?
- Age
- Geographical location
- Season
- Breed
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
What factors are associated with pre-test probability of PPID ?
- Age
- Clinical signs
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
How accurate is the basal ATCH assay in diagnosing PPID?
Basal ACTH concentration in aged horses showing specific clinical signs of PPID will have a high PPV based on a high pre-test probability.
Basal ACTH concentrations in young horses showing few or non-specific signs of PPID will have a lower PPV, based on a low pre-test probability.
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
How accurate is the TRH stimulation test in diagnosing PPID?
Where basal ACTH results fall in the equivocal zone, the TRH stimulation test can be used for further evaluation. It has increased accuracy in the diagnosis of PPID, particularly in subclinical cases.
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
What is the repeatability of TRH-stimulation test in mature horses ?
Good repeatability in non-autumn months when performed at intervals of 2–4 week. However, during the autumn, more variation should be expected.
Smaller response of ACTH to TRH stimulation when repeated within 1 day.
⇒ TRH simulation tests for PPID should not be performed at intervals shorter than 24 h.
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
How does the feeding affect basal ACTH or ACTH response (10 min) to TRH administration for diagnosing PPID ?
Conflicting results
There may be some effect of diet and/or feeding vs fasting on basal plasma ACTH concentrations, and fasting may also be relevant to TRH stimulation tests.
For repeated sampling of the same individual, it is prudent to test under similar dietary conditions.
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
What factors could influence basal ACTH concentration or ACTH response (10 and 30 min) to TRH administration for diagnosing PPID?
- Diet
- Critical illness
- Breed
- Transport or acute stress
- Mild to moderate pain
- Concurrent OST testing
- Coat color ? (Grey horses may have higher basal ACTH than non-grey horses in autumn.)
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
How does BCS affect basal ACTH concentration or ACTH response (10 and 30 min) to TRH administration for diagnosing PPID?
BCS may not impact testing for PPID
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
What are the effects of pergolide on ACTH tests in PPID horses ?
Pergolide treatment lowers basal ACTH concentrations and improves the ACTH response to TRH stimulation in most animals.
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
What are the effects of pergolide on clinical signs of PPID horses ?
Pergolide improves most clinical signs associated with PPID in most animals except laminitis
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
What dosage of pergolide mesylate can be used in donkeys?
What is the new hypothesis of absoption?
Pergolide mesylate administration to donkeys at 2 μg/kg bwt orally q24h (same as horses) → well-tolerated, with plasma concentrations similar to or higher than concentrations achieved in horses dosed similarly.
This study provides the first report of oral transmucosal abs° in equids.
Pharmacokinetic properties of pergolide mesylate following single and multiple-dose administration in donkeys (Equus asinus)
evj 2023
Which months have the lowest and highest TRH-stimulated ACTH concentrations?
TRH-stimulated ACTH concentrations were lowest in February-May and highest in August-October.
Evaluation of seasonal influences on adrenocorticotropic hormone response to the thyrotropin-releasing hormone stimulation test and its accuracy for diagnosis of pituitary pars intermedia dysfunction
Vet J 2023
What is the clinical implications of imprecise sampling time for 10- and 30-min TRH stimulation tests ? Which protocol to prefer ?
10-min protocol : In one report, sampling 1 min early or late resulted in deviation of the ACTH concentration by ≥10% in 75% of horses and led to an erroneous diagnosis of PPID status in 21% horses.
30-min protocol : The gradient of the ACTH response curve to TRH administration is flatter at this time, resulting in less minute-to-minute variation.
⇒ Imprecision of >1 min is likely to be more impactful for the 10-min protocol.
Clinical implications of imprecise sampling time for 10- and 30-min thyrotropin-releasing hormone stimulation tests in horses
evj 24
Does Chasteberry or cyproheptadine help in PPID horses ?
Chasteberry may improve some clinical signs of PPID but there is no proven effect on ACTH and there is no benefit to adding chasteberry to pergolide therapy.
Combination of cyproheptadine with pergolide is not superior to pergolide alone.
BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction
evj 2024
Laboratory findings with PPID?
Lymphopenia and/or neutrophilia (in the absence of infection)
Hyperglycemia
Hyperinsulinemia
Hypertriglyceridemia
Hypophosphatemia
High fecal egg count
Endocrinology group 2023
What are the consequences of PPID on muscles?
PPID affects muscle condition in horses by causing loss of topline muscle in early stages and topline muscle atrophy in advanced stages.
Endocrinology group 2023
What is the procedure for conducting TRH test?
- Collect blood into EDTA tubes at baseline
- Administer 0.5 mg (equids < 250 kg) or 1.0 mg (equids > 250 kg) of TRH intravenously
- Collect blood samples at 0 and exactly 10 minutes after TRH administration
- A second sample may also be collected 30 minutes after TRH administration if desired
Endocrinology group 2023
How to collect ACTH?
Collected into EDTA containing tubes
- Kept cool (ice packs or refrigerator) at all times
- Centrifuged and separated prior to shipping
- Shipped via overnight mail with ice packs
- Plasma can be frozen (centrifuged samples only) but avoid freeze-thaw cycles
Endocrinology group 2023
ACTH vary with seasons, review it.
PPID unlikely: (pg/mL)
dec-june < 15
july & nov < 15
august < 20
sept-oct < 30
PPID likely:
dec-june > 40
july & nov > 50
august > 75
sept-oct > 90
interpretive zone/grey zone between (CS, signalement)
Endocrinology group 2023
How should an older horse with advanced clinical signs be tested for suspected PPID?
Baseline ACTH → if grey zone ⇒ TRH-stimulation test → if grey zone ⇒ re-evaluate in 3-6 months
If generalized hypertrichosis → no test, treat directly its ok
If grey zone → use the lower threshold for diagnosis
Endocrinology group 2023
What are the recommendations for the management of PPID horse?
- Testing for PPID is not recommended in the absence of clinical signs.
- Assessment for insulin dysregulation should be pursued in all patients with PPID.
- Clinical signs and endocrine testing should be evaluated 1-3 months after starting treatment, and then every 6-12 months.
- Special considerations for wellness care in horses with PPID include:
- Regular attention to body condition, hoof care, dentistry, and parasite control
- Monitoring for bacterial infections
- Ensuring adequate water availability if polydipsia and polyuria are persistent problems
- Diet and exercise management for horses with PPID:
- Carefully monitor weight and body condition
- Feed selection based on body condition score and evidence for insulin dysregulation
- Obese horses should be placed on a lower energy diet and encouraged to follow an exercise program if soundness permits
- Horses with insulin dysregulation require lower non-structural carbohydrate feeds and limited access to pasture
- Monthly monitoring of BCS by owners is recommended
Endocrinology group 2023
What are the recommendation for treatment management of a PPID horse?
- The recommended initial treatment for PPID is Prascend® (pergolide tablets).
- The initial dosage of Prascend® (pergolide) for PPID treatment is 2 µg/kg (0.5 mg for a 250 kg pony and 1.0 mg for a 500 kg horse).
- If there’s no improvement in clinical signs or laboratory results, the pergolide dose can be gradually increased (1-2 µg/kg) then reassess (same season) 1-3months → if persistant therefore its a refractory case
- Strategies used for refractory cases include:
- Gradually increasing pergolide to 4-6 µg/kg (> 4 being off label) and adding cyproheptadine (0.25 mg/kg PO BID or 0.5 mg/kg PO SID)
- OR gradually increasing pergolide to 10 µg/kg (off label)
- In the event that a horse on pergolide treatment misses a dose, ACTH concentrations may begin to increase within 48 hours.
The most important is the clinical signs
Endocrinology group 2023
Does pergolide prolonge lifespan ?
No but improve quality of life
Endocrinology group 2023
How does TRH affect the pars intermedia in horses with PPID?
TRH stimulates receptors on melanotropes in the pars intermedia, leading to increased secretion of proopiomelanocortin (POMC)-derived peptides, including ACTH.
This response is exaggerated in horses with PPID compared to healthy controls
General knowledge. Evaluation of seasonnal influence on ACTH response to TRH test and its accuracy for diagnosis PPID
What are the potential side effects observed after TRH administration in horses?
Potential side effects include transient coughing, flehmen response, and yawning after administration.
Endocrinology group 2023
Which assessment is true about vitamin D status in horses ?
A- 25(OH)D3 is the predominant metabolite in horses, which is depending on season.
B- 25(OH)D2 is the predominant metabolite in horses, with a seasonal effect and without endogenous production of vitamin D3.
C- 25(OH)D3 is the predominant metabolite in horses, which is independent on season.
D- 25(OH)D2 is the predominant metabolite in horses, which is independent on season.
Answer B
In horses, 25(OH)D2 is the predominant vitamin D metabolite (from fungi on grass), and there is an apparent lack of endogenous vitamin D3 production.
In grazing ponies, 25(OH)D2 concentrations were significantly higher on long days compared to short days → seasonal effect.
The effect of season, management and endocrinopathies on vitamin D status in horses
evj 2023
What are the potential bone sequelae observed in horses with PPID?
Bone mineral density of lumbar vertebrae (nonweight bearing bones) can be decreased with PPID (L3, L4, L5) and could increase risk of developing pathological fractures. Not observed in weight bearing bones (third metacarpus or metatarsus)
Lumbar vertebral bone density is decreased in horses with pituitary pars intermedia dysfunction
evj 2024
What is the relationship between cortisol, ATCH and insulin in aged horses (> 15y) ?
There was no association between ACTH and cortisol.
Positive linear correlation between ACTH and post-OGT insulin in the autumn. In autumn, high ACTH was associated with ID, when no clinical signs of PPID were present.
Association between insulin dysregulation and adrenocorticotropic hormone in aged horses and ponies with no clinical signs of pituitary pars intermedia dysfunction
evj 2023
Does PPID have a clinical impact on mares’ reproductive performance?
The reproductive performance of the high ACTH group was significantly lower than the other groups.
Relationship between endogenous plasma adrenocorticotropic hormone concentration and reproductive performance in Thoroughbred broodmares
JVIM 2021
What is the clinical efficacy of canagliflozin in ID horses ?
A- Canagliflozin decreased mean insulin concentration during OST, decreased body weight and increased triglyceride concentrations.
B- Canagliflozin decreased mean insulin concentration during OST and decreased body weight of horses, and did not impact triglyceride concentrations.
C- Canagliflozin decreased mean insulin concentration during OST and increased triglyceride concentrations, but did non decrease body weight of horses.
D- Canagliflozin was uneffective in decreasing hyperinsulinemia in ID horses.
A- Canagliflozin decreased mean insulin concentration during OST, decreased body weight and increased triglyceride concentrations.
Canagliflozin is a promising drug for treatment of ID horses that requires future studies.
Short-term effects of canagliflozin on glucose and insulin responses in insulin dysregulated horses: A randomized, placebo-controlled, double-blind, study
jvim 2023
What is the clinical efficacy and side effects of ertugliflozin in HAL horses ?
After 30 days of treatment with ertugliflozin, there were:
- a reduction in insulin concentrations,
- lowering of insulin concentration in response to OST,
- improvement in modified Obel laminitis scores,
- increase in median serum triglyceride concentrations, but without any clinical signs of hyperlipaemia,
- 19% of PUPD during treatment.
Clinical efficacy observed by 4 days of TT.
Preliminary observations on the use of ertugliflozin in the management of hyperinsulinaemia and laminitis in 51 horses: A case series
eve 2023
Oral sugar test responses to ertugliflozin in ten horses with insulin dysregulation
eve 2024
Does continuous digital hypothermia effective in the treatment of hyperinsulinemic associated laminitis (HAL) ? What are the suspected mechanisms ? (3 points)
Continuous digital hypothermia (CDH) prevents lamellar failure in the euglycemic hyperinsulinemic clamp (EHC) model of laminitis. These data add further support for the use of CDH as a first aid treatment for severe acute laminitis associated with hyperinsulinemia in horses.
Suspected mechanisms of CDH:
- decrease of pro-inflammatory cytokines and chemokines,
- decrease in lamellar glucose metabolism without affecting glucose concentration,
- decrease perfusion.
Effect of digital hypothermia on lamellar inflammatory signaling in the euglycemic hyperinsulinemic clamp laminitis model
jvim 2020
The effect of continuous digital hypothermia on lamellar energy metabolism and perfusion during laminitis development in two experimental models
evj 2020
What is the mechanism of hyperinsulinemic associated laminitis during EHC model ?
A- Laminitis developed without evidence of lamellar hypoperfusion or energy stress. Therapies to improve perfusion are unlikely to affect the initial development of endocrinopathic laminitis.
B- Laminitis developed without evidence of lamellar hypoperfusion, but there was evidence of energy stress. Therapies to improve perfusion are unlikely to affect the initial development of endocrinopathic laminitis.
C- Laminitis developed with evidence of lamellar hypoperfusion, but no evidence of energy stress. Therapies to improve perfusion are likely to affect the initial development of endocrinopathic laminitis.
D- Laminitis developed with evidence of lamellar hypoperfusion and energy stress. Therapies to improve perfusion are likely to affect the initial development of endocrinopathic laminitis.
A- Laminitis developed without evidence of lamellar hypoperfusion or energy stress. Therapies to improve perfusion are unlikely to affect the initial development of endocrinopathic laminitis.
Lamellar energy metabolism and perfusion in the euglycaemic hyperinsulinaemic clamp model of equine laminitis
evj 2020
What changes are observed during laminitis models?
A- Hypoaminoacidemia
B- Hyperaminoacidemia
C- No impact of insulin on plasma amino acid concentration
D- Nobody knows
Hypoaminoacidemia develops in EHC and prolonged glucose infusion laminitis models.
This finding may have relevance to laminitis because hypoaminoacidemia affects cell adhesion and cytoskeletal dynamics in human cells.
Plasma amino acid concentrations during experimental hyperinsulinemia in 2 laminitis models
jvim 2021
What is the impact of intrasynovial triamcinolone treatment on the incidence of laminitis in a large population of sport horses ?
Intrasynovial triamcinolone acetonide administration does not increase the risk of laminitis in this study population.
A recent knowledge summary found “no conclusive evidence to support a causal association between therapeutic systemic corticosteroid administration and the development of laminitis in healthy adult horses/ponies”.
But a recent study showed that blood insulin and glucose concentrations modestly increased for 48 h following IA triamcinolone injection in horses without ID. Consequences on ID horses ?
Intrasynovial triamcinolone treatment is not associated with incidence of acute laminitis
evj 2021
Intra-articular triamcinolone acetonide injection results in increases in systemic insulin and glucose concentrations in horses without insulin dysregulation
evj 24
What is the prevalence and risk factors associated with laminitis in donkeys ?
Prevalence of laminitis in UK Donkey Sanctuary ∼49%
Risk factors differ from those reported in horses:
- more likely to be younger,
- less likely to get extra feed or have an additional medical problem,
- less likely to have undergone dental work, movement, imaging or surgery in the month preceding the episode.
Cross- sectional study to identify the prevalence of and factors associated with laminitis in UK donkeys
evj 2022
What is the current hypothesis regarding the pathophysiology of supporting limb laminitis (SLL) ?
Lamellar inflammatory signaling was higher in tissue from horses subjected to prolonged unilateral weight-bearing, suggesting that these pathways could be relevant to the pathophysiology of SLL.
Digital lamellar inflammatory signaling in an experimental model of equine preferential weight bearing
jvim 2023
Which diagnostic tests best quantify the risk of future laminitis development in nonlaminitic ponies ?
- Basal insulin (unfasted)
- OST (insulin T60 post corn syrup 0,3 mL/kg)
- Adiponectin concentration
- Divergent hoof growth
Predictors of laminitis development in a cohort of nonlaminitic ponies
evj 2023
A 22-year-old Thoroughbred gelding presents with a history of delayed shedding and mild lethargy. You decide to perform a thyrotropin-releasing hormone (TRH) stimulation test to evaluate for pituitary pars intermedia dysfunction (PPID). You perform the test once and get equivocal results. You’re considering repeating the test in 2 weeks. Which of the following statements is most accurate regarding the repeatability of the TRH stimulation test?
A) The test has excellent repeatability in both winter and autumn
B) The test has excellent repeatability in winter and is more variable in autumn (good reliability)
C) The test has poor repeatability in winter but excellent repeatability in autumn
D) The repeatability of the test is not affected by season
The correct answer is B.
Repeatability of a thyrotropin-releasing hormone stimulation test for diagnosis of pituitary pars intermedia dysfunction in mature horses
jvim 21
A 20-year-old mare presents with subtle signs of pituitary pars intermedia dysfunction (PPID), including mild hypertrichosis and decreased performance. You decide to perform a thyrotropin-releasing hormone (TRH) stimulation test to evaluate for PPID. You administer 1 mg of TRH intravenously and plan to collect a blood sample at exactly 10 minutes post-administration. However, due to an unexpected interruption, you collect the sample at 11 minutes instead.
Which of the following statements is most accurate regarding the impact of this 1-minute delay on the test results?
A) The delay will have no significant effect on the ACTH concentration or test interpretation.
B) The ACTH concentration will likely be higher than if sampled at 10 minutes.
C) The ACTH concentration will likely be lower than if sampled at 10 minutes.
D) The effect of the delay is unpredictable and equally likely to increase or decrease the ACTH concentration.
E) The delay invalidates the test results, necessitating a repeat test on another day.
The correct answer is C.
Effect of early or late blood sampling on thyrotropin releasing hormone stimulation test results in horses
jvim 22
In a clinical audit assessing the management of pituitary pars intermedia dysfunction (PPID) in equids, it was found that out of 459 animals with available records, 51.7% were classified as positive for PPID based on basal plasma adrenocorticotropic hormone (ACTH) concentrations. Among these positive cases, what percentage initiated treatment with pergolide mesylate as per the recommended guidelines?
A) 78.7%
B) 51.7%
C) 11.3%
D) 37.1%
Correct Answer: A) 78.7%
The audit revealed that 78.7% of the animals classified as positive for PPID (n=185 out of 235 positive cases) were treated with pergolide mesylate, indicating a significant adherence to treatment recommendations for this condition
Management of pituitary pars intermedia dysfunction in practice: A clinical audit
Vet J 22
A 12-year-old Welsh pony presents with a body condition score of 8/9 and a history of difficulty losing weight. The owner reports no previous episodes of laminitis but is concerned about the pony’s risk.
Which of the following diagnostic tests would be most appropriate to assess the pony’s risk of developing laminitis, and what result would indicate an increased risk?
A) Complete blood count
B) Serum chemistry panel
C) Basal insulin
D) Radiographs of the front feet
E) ACTH stimulation test
C. Basal insulin
2020 Clinical insights: Equine obesity
How does the function of the enteroinsular axis differ in horses with equine metabolic syndrome compared to healthy horses?
In horses with EMS, there appears to be increased glucose uptake from the intestines, possibly due to an intestinotrophic effect of GLP-2. This leads to higher glucose levels stimulating more insulin secretion.
Additionally, there is likely an exaggerated incretin effect, where gut hormones like GLP-1 and GIP further stimulate insulin release from the pancreas beyond just the glucose effect.
This results in post-prandial hyperinsulinemia in horses with ID.
Equine metabolic syndrome: Role of the enteroinsular axis in the insulin response to oral carbohydrate
Vet J 23
A 15-year-old horse presents with progressive weight loss over 6 months, lethargy, and mild intermittent lameness. Blood tests reveal hypercalcemia and elevated parathyroid hormone (PTH) levels.
What is the most appropriate diagnostic approach to confirm a suspicion of primary hyperparathyroidism?
The most appropriate diagnostic approach would be to combine ultrasonography and technetium-99m sestamibi scintigraphy.
Justification:
This approach is justified by data from paper 2 (Gorenberg et al., 2020) which reports that:
Ultrasonography has a sensitivity of 54% (7/13 cases)
Technetium-99m sestamibi scintigraphy has a sensitivity of 81% (13/16 cases)
The combination of both techniques has a success rate of 90% (9/10 cases)
Furthermore, the described clinical signs (weight loss, lethargy, lameness) correspond to signs reported in 71% of cases (12/17) for weight loss and are consistent with other signs mentioned in paper 1 (Johnson and Townsend, 2023).
Diagnosis and treatment of confirmed and suspected primary hyperparathyroidism in equids: 17 cases (1999–2016)
evj 20
In a 12-year-old dressage horse diagnosed with pituitary pars intermedia dysfunction (PPID) and presenting with mild lameness, what are the most important factors to consider in developing a comprehensive management plan to maintain athletic performance and reduce the risk of complications?
Endocrine management:
Initiate pergolide treatment for PPID
Monitor insulin levels, as 16% of horses with PPID also have insulin dysregulation (ID)
Lameness evaluation:
Assess for suspensory ligament injury, as it’s the site of greatest soft tissue injury in equine athletes (approx. 14% overall, >25% in dressage horses)
Consider that PPID is associated with higher suspensory ligament degeneration
Exercise and diet plan:
Implement low-intensity exercise to improve insulin sensitivity and improved the ratio between neck circumference and height at withers
Consider a low-starch diet
Laminitis prevention:
Monitor closely for signs of laminitis, as it’s secondary to high insulin in EMS or PPID
Be aware of the 34.1% recurrence rate within 2 years for hyperinsulinemia-associated laminitis
Muscle and back health:
Address potential muscle wasting along the topline, which can affect saddle fit and cause back pain
Implement dynamic mobilization exercises, as pergolide treatment alone doesn’t improve muscle mass in PPID horses
Be aware that 74% of horses with back pain were lame, and 32% of lame horses had back problems
Regular monitoring:
Conduct frequent body condition scoring, as over 30% of horses in some regions are overweight or obese
Monitor for signs of systemic inflammation, which is linked to obesity and common in EMS/ID
A one-health lens offers new perspectives on the importance of endocrine disorders in the equine athlete
Which plants are responsible of vitamin D toxicity ?
Solanum spp.
What influence do the following factors have on thyroid hormone secretion?
- Age
- Gender and Breed
- Physiologic status (pregnant, lactating)
- Hormones
- Drugs
- Season and daily rythm
- Activity
- Feeding
- Age : very high at birth and decrease with age. Foals → x10 than adults
- Gender and breed : stallions TH < mares. Donkeys TH > horses.
- Physiologic status : pregnant mares, lactating mares → increase TH
- Hormones : endogenous or exogenous glucocorticoids → decrease TH release ; catecholamines → increase TH.
- Drugs : goitrogenic substances (antithyroid activity) → PBZ, sulfonamides, phenothiazines (ACP)…
- Season and daily rythm : cold T° → ⊕ HPTA ; diurnal rythmicity related to diurnal variations of glucocorticoids → peak TH around 4 pm.
- Activity : prolonged exercise can ↘︎ TH.
- Feeding : high carbohydrates diet → insulin release → ↗︎ TH ; starvation (negative energy balance) → ↘︎ TH
Reed
EEG 23
What is the nonthyroidal illness syndrome ?
Illness, systemic inflammation, stress and starvation → ↗︎ pro-inflam. cytokines, glucocorticoids, leptin → ⊖ HPTA → low TH but this is not hypothyroidism.
Also low TH concentrations commonly measured in EMS (insulin resistance) and laminitic horses. Exogenous supplementation of TH (levothyroxine) in obese horses ? Watch out for iatrogenic hyperthydoidism.
EEG 23
What are the clinical signs of hypothyroidism in adult horses ?
Cold intolerance, low body T°, bradycardia, and haircoat abnormalities.
EEG 2023
How to interpret a low serum tT3 and tT4 in an adult horse ?
A diagnosis of hypothyroidism is only appropriate when results of a thyroid function test confirm that the thyroid gland cannot respond adequately to stimulation.
Hypothyroidism should not be diagnosed in horses based on blood thyroid hormone concentrations alone. For example, low tT3 and/or tT4 concentrations occur in horses receiving phenylbutazone.
EEG 23
Then, how to diagnose hypothyroidism in adult horses ?
1- Low serum tT4 +/- tT3
2- Is there a plausible explanation ? drugs, stress, starvation…
3- If no, check serum free t4 (fT4) concentration by equilibrium dialysis method (only accurate way).
4- If low, perform a TRH stimulation test. If no response → HYPOTHYROIDISM and treatment with levothyroxine might be justified at this point.
EEG 23
What is the clinical significance of TSH-stimulation test ?
Little used of this test (cost, availability)
Injecting 2.5 to 5 UI of TSH IV
Normal horses : T3 peak at 2h and T4 peaks at 3-4h (T3 before T4)
Insufficient hormonal response → primary hypothyroidism
PBZ → no influence
Dexamethasone → blunts TH response to TSH-stimulation
What is the clinical significance of TRH-stimulation test ?
Widely used method to assess thyroid gland function and PPID
The protocol is to collect serum for baseline serum tT3 and tT4 measurements, administer 1 mg TRH IV, and then measure the serum tT3 concentration 2 hours later and serum tT4 concentration 4 hours later.
> x1.5 increases in blood tT3 and tT4 concentrations are normally detected
Inadequate TH response → primary (thyroid) or secondary (pituitary) hypothyroidism.
NB : measurement of endogenous TSH is not available in horses.
Tertiary hypothyroidism = hypothalamic disorder
Side effects of TRH administration include coughing, muscle fasciculations, chewing, and exhibition of the Flehmen response.
EEG 23
What are the clinical signs of hyperthyroidism ?
Weight loss, hyperexcitability, polyphagia, tachycardia, polydipsia, and goiter.
EEG 23
What is the clinical significance of thyroid suppression test ?
Blood tT3 and tT4 concentrations are often 2-3 times higher than normal in hyperthyroidism horses.
Exogenous adm° of T3 → should inhibit TSH and TH secretion (↘︎ T4).
No changes = primary hyperthyroidism (adenocarcinoma = functional thyroid gland tumor)
How to assess a goiter in an adult horse ?
Enlarged thyroid glands (goiter) in adult horses are most often caused by benign adenomas with cysts as a less common cause. These enlarged glands do not affect thyroid function and simply require monitoring over time.
Functional thyroid gland tumors (adenocarcinomas) are rare and usually accompanied by clinical signs of hyperthyroidism (e.g., weight loss or agitation on rare occasions).
Ultrasound examination is the best way to evaluate an enlarged thyroid gland. Tumors may be solid or have a characteristic cystic appearance.
BIOPSY OF THE GLAND IS NOT RECOMMENDED as the thyroid is an extremely vascular organ that bleeds profusely and percutaneous biopsy samples can be non-diagnostic.
EEG 23
Which horses seem predisposed to thyroid tumors ?
Old horses from lightweight breeds.
Most common → adenoma, benign, unilateral and not associated with thyroid dysfunction.
Adenocarcinoma : malignant
Medullary carcicnoma : hyperthyroidism, old horses
Multiple endocrine neoplasia (pheochromocytoma…)
Reed
What external factors could increase thyroid hormones ?
Transport,
high-carbohydrate or fat meals
EEG 23
What is the relationship between EMS and hypothyroidism ?
Low serum tT3 and tT4 concentrations are detected in many EMS horses and ponies, and this is to be expected given the endocrine and metabolic disturbances that are components of this syndrome.
We can therefore think of EMS as a nonthyroidal illness, and blood tT3 and tT4 concentrations are low for this reason.
Levothyroxine can be administered at a high dose for 3-6 months to accelerate weight loss in obese EMS horses, but this is not evidence of hypothyroidism.
EEG 23
What is the clinical significance of goiter in foals ?
Goiter = enlarged thyroid gland for any reason. Goiter does not imply hypo- or hyperthyroidism ! Functional tests are necessary.
Main cause of neonatal hypothyroidism and goiter : nutritional → decreased iodine intake. Poor prognosis.
Congenital goiter : inadequate or excessive iodine intake by the mare.
Premature and septic foals : ↘︎ TH but not hypothyroidism → NTIS
What are the clinical signs of hypothyroidism in foals ?
Unlike adult horses, hypothyroidism in foals is well documented and results in a cluster of clinical signs.
Most of the clinical signs are characteristic of dysmaturity, although prognathism is unique to hypothyroidism. cf photo
+ forelimb contracture
Pregnant mares should not receive high iodine supplements, not be kept on fescue pasture in late gestation, or not be allowed access to plants that contain goitrogens.
EEG 23
What are the consequences of supra-physiologic thyroxine supplementation in racehorses ?
Supra-physiologic thyroxine supplementation caused a decreased V200 during a standard exercise test and may result in cardiac arrhythmias (AF ++).
A randomised, controlled trial to determine the effect of levothyroxine on Standardbred racehorses
evj 22
What is the most prevalent complication of thyroidectomy ?
A major concern during thyroidectomy is the direct intraoperative visualisation of the RLN to avoid iatrogenic damage, which has been reported to have a prevalence of 50% in horses.
Can be avoided by the use of intraoperative neuromonitoring of the RLN, a superior method that allows identification and preservation of the nerve.
Thyroidectomy facilitated with Harmonic Caliper and intraoperative neural monitoring in three horses
eve 23
What is anhidrosis ?
Inability of horses to sweat in response to appropriate stimulation.
Partial anhydrosis → most common.
Frequent in the tropics and areas with high T°C and humidity → prevalence in southern US ∼ 6-20%
Not associated with exercise but environmental conditions + genetic component (familial tendency)
NB : PPID → anhidrosis
Why foals are commonly affected by the anhidrosis ?
Drug-induced anhidrosis → likely cause of hyperthermia in foals treated with macrolide, particularly erythromycin
How to diagnose anhidrosis ?
Clinical signs : depression, anorexia, poor performance, tachypnea, hyperthermia, complete or partial decreased sweating, alopecia…
Sweating is due to the stimulation of β2-adrenergic receptors by catecholamines.
Diagnostic test : intradermal injection of epinephrine (not specific to β2) or salbutamol, terbutaline (specific to β2) → delayed or no sweating response.
How to manage a post-exertional hyperthermia ?
Resolving in 3 to 7 days with supportive management : cooling the environment, alcohol baths, cooled IV fluids.
Then, dietary modification ?
Sodium levothyroxine ? TH increase β2-adrenoreceptor sensitivity.
What is the clinical efficacy of Chinese herbs and acupuncture to treat equine anhidrosis ?
Ratios of sweat responses were higher in treatment horses 2 days after treatment, compared to baseline, but not 4 weeks after treatment.
The efficacy of a traditional Chinese veterinary medicine protocol for anhidrosis treatment with acupuncture and Chinese herbs was low but higher in treated horses compared with placebo.
Efficacy of treatment of equine anhidrosis with acupuncture and Chinese herbs is low but higher in treated horses compared with placebo
javma 24
What are the most presenting complaints in case of hyperparathyroidism ?
The most common presenting complaints were weight loss (12/17) and hypercalcemia (10/17).
Diagnosis and treatment of confirmed and suspected primary hyperparathyroidism in equids: 17 cases (1999–2016)
evj 20
What is the correlation between pain, cortisol and ACTH ?
The significant correlation identified between composite pain scale (CPS) score and [cortisol] in medical and surgical colic cases provides physiological validation of pain scores as a marker of underlying stress in horses with colic.
No significant association was found between CPS score and [ACTH].
Application of an equine composite pain scale and its association with plasma adrenocorticotropic hormone concentrations and serum cortisol concentrations in horses with colic
eve 20
What is the definition of Equine Metabolic Syndrome ?
Equine metabolic syndrome (EMS) is a collection of risk factors highly associated with an increased risk of hyperinsulinemia-associated laminitis (HAL) and potentially other morbidities.
Insulin dysregulation (ID) is a consistent feature of EMS and increased generalized or regional adiposity is typical. Additional factors present in some animals include altered adipokine and postprandial incretin concentrations, hypertriglyceridemia, and hypertension.
Equine Endocrino Group 22
What is the definition of insulin dysregulation ?
Insulin dysregulation is detected in all equids with EMS.
Insulin dysregulation is defined as any combination of basal (resting) hyperinsulinemia, postprandial hyperinsulinemia (response to oral sugar test [OST] or consumed feeds), or tissue insulin resistance (IR; hepatic and/or peripheral).
Insulin dysregulation is the central endocrine disorder of EMS.
Equine Endocrino Group 22
How does hyperinsulinemia cause laminitis in equids?
The characteristic histopathological changes of HAL are stretching and elongation of the lamellae without disruption of the basement membrane.
The most popular theory is that hyperinsulinemia induces inappropriate stimulation of insulin-like growth factor-1 receptors on lamellar epidermal cells.
Equine Endocrino Group 22
Can horses with pituitary pars intermedia dysfunction (PPID) have HAL?
HAL is detected in approximately 30% of horses with PPID and horses greater than 10 years of age should be tested for PPID as well as ID.
Equine Endocrino Group 22
Which dynamic tests are recommended to diagnose EMS ?
Oral sugar test (OST) to assess postprandial insulin response, which reflects a more complete sequence of events including digestion and absorption of sugars, incretin hormone responses, secretion of insulin from the pancreas and risk of HAL.
Insulin tolerance test (ITT) to assess insulin sensitivity, which focuses solely upon hepatic and/or peripheral tissue insulin sensitivity.
(cf photo)
Equine Endocrino Group 22
What is the most sensitive and specific test to diagnose ID in ponies between basal insulin concentration, OST and ITT ?
Is this test correlated with risk of laminitis ?
Basal insulin (BI) → Se 52% ; Spe 97% (low sensitivity)
OST → Se 84% ; Spe 60% (low specificity)
ITT → Se 85% ; Spe 88%
But only BI and the OST were associated with laminitis
Evaluation of field-testing protocols to diagnose insulin dysregulation in ponies using a Bayesian approach
vet J 2023
How do you diagnose an EMS horse in practice?
Two-step approach to diagnosing ID: Testing can be performed in two steps if the owner raises concerns about dynamic tests inducing laminitis.
- The first step is to measure the resting (basal) insulin concentration to screen the horse for hyperinsulinemia and assess laminitis risk (low Se / high Spe).
- If the resting insulin concentration is normal, a dynamic test must still be performed as a second step because resting measures have low diagnostic sensitivity. An OST is also recommended when only mild hyperinsulinemia is detected to estimate insulin responses to grazing on pasture or feeds.
Equine Endocrino Group 22
What is the clinical utility of dosing blood glucose concentration during OGT ?
The variability in these data support that basal and post-prandial blood glucose responses to an OGT are not appropriate as stand-alone diagnostic markers of ID
or PPID.
However, the association between blood glucose and cresty neck score supports the use of cresty neck score when evaluating animals for ID.
Diagnosis of equine endocrinopathies: The value of measuring blood glucose during an oral glucose test
Vet J 23
Which additional test for assessment of horses with EMS can be used ?
Adipokines = cytokines of adipose tissue (leptin, adiponectin)
- Leptin : Higher leptin concentrations are associated with increased adiposity and metabolic derangement. Useful for providing evidence of increased internal adiposity. This hormone is more directly associated with obesity than ID.
- Triglyceride : Hypertriglyceridemia associated with ID and obesity, exacerbated by negative energy balance. Hypertriglyceridemia is a predictor of laminitis risk in ponies.
- Adiponectin : Total adiponectin concentrations < 7.9 ug/mL are consistent with EMS and an increased risk of laminitis.
Equine Endocrino Group 22
Is there any influence of season on basal insulin concentration ?
Insulin concentrations are affected by season, with higher concentrations detected in December, January, and February in the Northern hemisphere, suggesting a winter-associated exacerbation of ID.
But neither OST results nor adiponectin varies with season.
Equine Endocrino Group 22
Variation in insulin response to oral sugar test in a cohort of horses throughout the year and evaluation of risk factors for insulin dysregulation
evj 22
Which medical therapy can be used for EMS horses ?
1- Manage diet : hay ∼ 1.5% BW in dry matter, NSC content < 10% (NSC appears to be the main driver of the postprandial insulin response), restrict grazing, do not feed grain or treats. Or soak hay in cold water for at least 1h.
2- Manage exercise when laminitis is resolved. Low intensity exercise for > 30 min, > 3 times a week. Lack of exercise was a risk factor for ID.
3- Medical therapy :
- High-dose levothyroxine : for cases with weight loss resistance. Administer levothyroxine at a high dose of 0.1 mg/kg daily in the feed. Maximum 3-6 months.
- Sodium-glucose co-transporter 2 (SGLT2) inhibitors : Used when horses are affected by laminitis and severe ID are not responding to other measures. Canagliflozin (0.5 mg/kg, PO, q24h) and ertugliflozin (0.05 mg/kg POq24h). Hypertriglyceridemia might develop as a consequence, monitor TG at 7 and 14 days, and then every 1-3 months thereafter.
- Metformin hydrochloride : For animals with persistent hyperinsulinemia, even after management changes have been followed. The drug is only effective in a small percentage of horses and may lose efficacy over time. Administer 30 mg/kg metformin hydrochloride in the feed or by mouth, ideally 30 minutes prior to feeding or turnout, up to 3 times daily
Equine Endocrino Group 22
Postprandial insulin responses to various feedstuffs differ in insulin dysregulated horses compared with non-insulin dysregulated controls
evj 22
Variation in insulin response to oral sugar test in a cohort of horses throughout the year and evaluation of risk factors for insulin dysregulation
evj 22
What are the most commonly reported initial adverse effects of SGLT2 by owners ?
114 owners (33.3%) reported one or more initial adverse effects upon induction onto the medication, particularly excessive urination (n = 70, 20.5%), excessive drinking (n = 38, 11.1%), excessive weight loss (n = 34, 9.9%) and dullness (n = 26, 7.6%).
Ertugliflozin was the most commonly prescribed SGLT2i (79.8%), and the most common reasons for treatment were high insulin concentrations (84.2%) and active laminitis (59.7%).
The use of SGLT2i in horses was associated with excellent rates of owner satisfaction and owner-reported improved quality of life for the horse; however, some
adverse effects were observed.
Horse owner experiences and observations with the use of SGLT2i for the management of equine metabolic syndrome and hyperinsulinaemia- associated laminitis
eve 24
What are the effects of pre-dosing with metformin on the insulin response to OST in ID horses, in a recent study ?
Metformin treatment had no significant effect on plasma glucose, insulin or C-peptide concentrations at any time point compared with placebo in ID horses.
The results do not support the use of targeted metformin treatment to reduce post-prandial hyperinsulinaemia in horses with naturally-occurring ID.
The effect of pre-dosing with metformin on the insulin response to oral sugar in insulin-dysregulated horses
evj 24
Which phenotypic markers are associated with insulin dysregulation ?
In the final multivariable model, only obesity (body condition score ≥8) was associated with ID.
Because obesity is associated with ID in cold-blooded type horses, objective monitoring of phenotypic markers by owners may be beneficial for health outcomes.
Insulin dysregulation in a population of Finnhorses and associated phenotypic markers of obesity
jvim 20
What is the effect of alpha-2-agonists administration in glycemia and insulinemia in healthy and ID horses ?
A- increase glycemia and insulinemia in ID horses, but not healthy horses
B- increase glycemia and insulinemia in ID and healthy horses
C- increase glycemia but not insulinemia in ID horses, but not healthy horses
D- increase glycemia but not insulinemia in ID and healthy horses
Answer B
Alpha-2-agonists suppress insulin secretion with transient hyperglycemia and rebound hyperinsulinemia in metabolically stable horses and ID horses.
In ID horses, detomidine could minimize hyperinsulinemia when compared to xylazine.
Alpha-2-antagonist, vatinoxan, was effective in preventing detomidine-induced hyperglycaemia as well as the subsequent insulin increase in horses with ID, and after oral carbohydrate load.
Blood glucose and insulin concentrations after alpha-2-agonists administration in horses with and without insulin dysregulation
jvim 20
The effects of an alpha-2-adrenoceptor agonist, antagonist, and their combination on the blood insulin, glucose, and glucagon concentrations in insulin sensitive and dysregulated horses
Vet J 21
Effects of alpha-2-adrenoceptor agonism and antagonism on equine blood
insulin and glucose concentrations after oral carbohydrate load
Vet J 24
Is there association between L-lactate concentrations and ID horses ?
Between sphingolipid concentrations and ID horses ?
Results do not support an effect of endocrine status on L-lactate concentrations in blood of ponies.
Positive correlation between the insulin response and sphingolipid concentrations → upregulated sphingolipid metabolism in ID horses.
A high plasma ceramide concentration can indicate insulin dysregulation in horses.
Associations of plasma sphingolipid profiles with insulin response during oral glucose testing in Icelandic horses
jvim 21
Influence of endocrine disease on l-lactate concentrations in blood of ponies
jvim 21
What are the effects of obesity on blood pressure, insulin resistance and serum cortisol concentrations ?
Obesity induced by high fatty and low NSC haylage was associated with increase in blood pressure and an increase in serum cortisol, that was not associated with insulin sensitivity.
The effect of diet-induced obesity and pasture on blood pressure and serum cortisol in Standardbred mares
evj 21
What is associated with hyperinsulinemia and EMS ?
- low kynerenin / tryptophan ratio
- high arginine and carnitine
- low arginine and carnitine
- high kynerenin / tryptophan ratio
Our results suggest induction of low-grade inflammation during the OGT.
Plasma arginine and carnitine concentrations were
lower in horses with high insulin response and could constitute potential therapeutic targets.
Development of screening tools to identify insulin-dysregulated horses using only baseline blood sample appears promising.
Metabolic changes induced by oral glucose tests in horses and their diagnostic use
jvim 21
What is not a risk factor for EMS ?
- Hoof growth rings
- Leisure activity
- Breeding activity
- Increasing age
- BCS ≧ 7/9
Risk factors associated with a diagnosis of EMS included ageing, being female, more sedentary main activity, obesity (cresty neck score), and shorter periods on pasture during the summer.
Clinical manifestations of hoof growth ring and supraorbital fat scores of 3/3 were more frequent in EMS ponies.
Not related to breeding activity.
Equine metabolic syndrome in UK native ponies and cobs is highly prevalent with modifiable risk factors
evj 21
Epidemiological investigation of insulin dysregulation in Shetland and Welsh ponies in Australia
evj 24
Is there any impact of obesity and ID on coagulability ?
Obese, insulin-dysregulated horses are hypercoagulable compared to healthy controls.
Thromboelastography in obese horses with insulin dysregulation compared to healthy controls
jvim 22
How to restrict grazing in ponies ?
Strip grazing limited pony bodyweight gains and upward changes in morphometric parameters. The dry matter (DM) herbage yield of each paddock was determined, and paddock length adjusted to provide 1.5% of individual pony BW as herbage DM daily.
Strip-grazing: Reduces pony dry matter intakes and changes in bodyweight and morphometrics
evj 22
Can the HMGA2:c.83G>A variant be used as a genetic marker to identify ponies at increased risk for insulin dysregulation?
The study found that the HMGA2:c.83G>A variant was associated with both decreased height and higher basal insulin concentrations across pony breeds.
Ponies with at least one copy of the A allele (A/G and A/A) had significantly higher insulin concentrations compared to G/G individuals.
This suggests that the HMGA2:c.83G>A variant could potentially be used as a genetic marker to identify ponies at increased risk for insulin dysregulation. However, as insulin dysregulation is a complex trait influenced by multiple genes and environmental factors, this single variant alone may not be sufficient for accurate risk prediction.
Evaluation of an HMGA2 variant contribution to height and basal insulin concentrations in ponies
Does sirolimus administration reduce insulin responses in horses with insulin dysregulation?
Sirolimus : aka rapamycin, is an immunosuppressive drug.
Yes, this study found that sirolimus decreased the insulinemic response to glucose in both healthy horses and those with experimentally-induced insulin dysregulation. Warrants further investigation.
Minimal effect on glucose concentration.
Effect of sirolimus on insulin dynamics in horses
jvim 23
Is there a threshold for NSC above which there is an exagerated insulin response in ID horses ?
Based on this study, ID horses seem to have an apparent threshold for NSC of around 0.1 g/kg BW /meal (NCS < 10% ?), above which significantly increased insulin responses are seen compared with non ID horses.
Identifying possible thresholds for nonstructural carbohydrates in the insulin dysregulated horse
evj 23
In a 15-year-old overweight pony with suspected insulin dysregulation, how do the diagnostic accuracy and ease of administration of the new GC pellets (DysChEq™) compare to the traditional oral glucose test via nasogastric tube?
The oral glycemic challenge (GC) pellets (DysChEq)™ and GC syrup can be used as palatable and well-accepted oral GC tests for assessment of ID in horses.
Based on the study results, the new GC pellets (DysChEq™) offer comparable diagnostic accuracy to the traditional oral glucose test via nasogastric tube, with several advantages in ease of administration.
Palatability, glycemic, and insulinemic responses to various carbohydrate formulations: Alternatives for the diagnosis of insulin dysregulation in horses?
jvim 23
What is the impact of giving a starch-rich treat each day to ponies ?
A bread-based treat was offered twice daily for 10 days, adding 0.36 g/kg body weight (BW) carbohydrates (> 0.1 g/kg BW/ meal previously recommended) to the daily diet.
The absorption of D-xylose increased 1.6-fold after 10 days of eating the treat. A small amount of additional carbohydrate each day in the form of a treat can cause a measurable change in the enteroinsular responses to eating.
A starch-rich treat affects enteroinsular responses in ponies
javma 22
What is the difference between OGT and ITT ?
Can one test replace another for the diagnosis of ID?
IV tests (ITT) mainly focus on peripheral insulin resistance (IR), while oral tests (OGT) assess postprandial hyperinsulinemia (HI), which are different aspects of ID.
In this study, while 6/12 horses were identified as HI by the OGT, all 12/12 horses were identified as IR by the modified 2-step ITT underlining the importance, but difficulty in choosing the right diagnostic tool in clinical settings to assess ID.
NB : A recent study comparing recombinant regular human insulin and porcine zinc insulin (PZI) showed that when using the ITT-PZI, an adjusted cut-off value for blood glucose reduction of 40 % at 30 min resulted in better test performance.
Comparison of a modified 2-step insulin response test performed with porcine zinc insulin and an oral glucose test to detect hyperinsulinemic Icelandic horses
Vet J 23
Evaluating insulindysregulation in horses: A two-step insulin-tolerance test using porcine zinc insulin
Vet J 24
What are the effects of PBZ adm° in ID horses ?
- Increase glucose and insulin concentrations post OGT
- Decrease glucose and insulin concentrations post OGT
- Increase glucose and insulin concentrations post ITT
- Decrease glucose and insulin concentrations post ITT
Phenylbutazone administration in horses with ID decreases glucose and insulin concentrations in response to an OGT warranting further investigation of a therapeutic potential of phenylbutazone in the management of hyperinsulinemia-associated laminitis beyond analgesia.
No significant effect was detected in control horses.
Effect of phenylbutazone on insulin secretion in horses with insulin dysregulation
jvim 24
Can adiponectin dosage be estimated from BCS?
Morphometric measures such as BCS do not closely reflect [total adiponectin].
Circulating [total adiponectin] and [basal insulin] should be determined in all animals with predisposing factors, regardless of obesity status.
Relationships between total adiponectin concentrations and obesity in native-breed ponies in England
evj 24
Does glucagon-like peptide-1 could be used as an adjunctive diagnostic test for ID ?
No.
No difference in GLP-1 response was detected according to ID or IR status, despite there being strong positive correlations between GLP-1 and insulin concentrations measured at individual time points.
These data do not support of the use of GLP-1 as an adjunctive diagnostic test for ID or IR, as defined by conventional intravenous or oral dynamic tests.
Investigation of glucagon-like peptide-1 response to six oral carbohydrates
in ponies
Vet J 24
