Lecture 13: Approach to Endocrine Disease Flashcards
Why can diagnosing endocrine diseases be challenging (especially Cushing)
seasonal changes in hormones affect test interpretation
where does PPID affect in body
pars intermedia
PPID is the result of loss of __of the pars intermedia a
dopaminergic inhibition
how does dopamingeric inhibition work in healthy horse pars intermedia
dopaminergic neurons inhibit the pars intermedia and therefore limit release of ACTH and related peptides
Describe what happens when you lose dopaminergic inhibition in PPID and what causes it
pars intermedia hyperplasia/adenoma—> loss of dopaminergic inhibition -> increased release of aCTH and related peptides
what products are released from pars intermedia
POMC—> ACTH and B-endorphin
ACTH—> a-MSH and CLIP
what cleaves ACTH to a-MSH and CLIP in normal horses
prohormone convertase 2 (PC2)
is PPID a condition of older or younger horses
older
what are some clinical signs of PPID
- Hirsutism
- Muscle wasting/weight los
- PU/PD
- Hyperhydrosis
- Immunosupression
- Behavior changes
- Infertility
- Blindness
- Regional adiposity and insulin resistance
- Inappropriate lactation
what early/subtle clinical findings is highly suggestive of PPID
regional hypertrichosis/delayed shedding
what is an advanced sign strongly suggestive of PPID
generalized hyerptrichosis
what is the protocol for testing for PPID with few, mild or early clinical signs in younger horse
- TRH stimulation test and assess insulin status
- Results in interpretative zone of PPID unlikely zone—> recheck 3-6 months
- Results supportive of PPID—> start pergolide
What is protocol for testing for PPID when there are many, severe, more advanced clinical signs, older horse
- Baseline ACTH test and assess insulin status
- Results unlikely zone—> TRH stimulation test—> if supportive of PPID start pergolide or if unlikely zone recheck in 3-6 months
what test is recommended for early PPID
TRH stimulation test with ACTH measured
what test is recommended for advanced PPID
basal ACTH concentration
a Dexamethasone suppression test can be used to dx PPID, but why is it risky
increase risk of laminitis
what tests are not appropriate to dx PPID
- ACTH stim test
- Baseline cortisol
- Diurnal cortisol rhythm
- TRH stim with cortisol measured
what is procedure for doing baseline ACTH test
- Collect in EDTA (purple top) tube
- Keep on ice
- Centrifuge
what is procedure for TRH stimulation test
- Keep horses off grain
- Give TRH IV
- Collect in EDTA (purple top) tube at 0 minutes and 1-0 minutes
currently there is no normal TRH stimulation result between what months, but a __ test is likely valid
july and December, negative
what is MOA of pergolide/prascend
dopamine receptor agonist- restores inhibition of melanotropes
do not exceed what dose of pergolide
0.01mg/kg
t or f: pergolide cures PPID
false- manages disease
what other drug can be added as adjunct to pergolide to tx PPID and what is MOA
cyproheptadine- serotonin antagonist, antihistamine activity, anticholinergic
what comorbidities do you want to test for in PPID patient
- BCS
- FEC
- Baseline lateral films- laminitis
- Baseline bloodwork
what lab findings besides increase ACTH are often found in PPID patients
lymphopenia/neutrophilia, hyperglycemia, hyperinsulinemia, hypertriglyceridemia, hypophosphatemia, high fecal egg count
what are the most characterizing clinical signs of equine metabolic syndrome
- general or regional adiposity
- Insulin resistance- hyperinsulinemia
- Predisposed to laminitis
based on the appearance of this horse- what endocrine disease is more likely- PPID or EMS
EMS- crust neck, fat pads
Normal hair coat so unlikely PPID
what horses have genetic predisposition to EMS
Pony breeds, andalusians, Morgans, minis, warm bloods
what is the algorithm to diagnose EMS
- Test for insulin dysregulation and PPID
- Negative- manage obesity or PPID
- Positive and obese ID—> limit calories, low carb diet—> normalize insulin recheck 6 months, but if remains ID—> pharmacological intervention
- Positive and non-obese ID—> maintain body condition- lower carb, high fat diet—> normalize ID check q6 months or remains ID—> pharmacological intervention
what tests can be done to dx EMS
- Resting insulin concentrations
- Dynamic insulin testing
- Leptin
- Triglycerides
when doing resting insulin concentrations for EMS horses can’t have grain within __hrs
4hrs
what resting insulin concentration is diagnostic
> 50uU/L
how do you do dynamic insulin testing for EMS
oral sugar test with corn syrup, measure insulin and glucose, >45uU/L diagnostic
leptin is produced by __ cells
adipose cells
T or f: high leptin alone can indicate insulin resistance
false
PPID or EMS: normal leptin and insulin resistance
PPID
PPID or EMS: high leptin and insulin resistance
EMS
t or f: thyro-L is an appropriate tx for EMS
false- can be appropriate if unable to exercise b/c of laminitis
what is first line treatment for EMS
dietary modification and exercise
Case ex: 19yr Tennessee Walking Horse, mare. Walking on eggshells T=100.9, P=48, R-16, BCS: 4/9. What is gait indicative of
laminitis
what dietary modifications should be made in EMS or PPID to address insulin resistance
reduce starch, grass hay
what is anhydrosis
lose ability to sweat
what are some possible causes of anhidrosis
- Down regulation of B2 adrenergic receptors
- Decreased stimulation of receptors
- Aquaporin-5 water channel dysregulation
what are the equine sweat glands and what are each important for
- Humoral- B2 adrenergic secreted from adrenal medulla, more important in exercise
- Nervous- autonomic adrenergic nerves, most consistently important
how can you test anhidrosis
terbutaline test
did a terbutaline test on 3 horses for anhidrosis- what horse is normal, partial sweater and and anhidrotic horse
- Normal
- Partial sweater
- Anhidrotic horse
how do you manage anhidrosis
- Move horse to drier climate
- Diet/electrolytes (potassium)
- A/C supplement (L-tyrosine, ascorbic acid, niacin, cobalt)
how does L-tyrosine work to manage anhidrosis
precursor of dopamine/catecholamines may help desensitize B-2 receptors
what triggers hyperlipidemia/hyperlipemia
negative energy balance—>fat stores mobilized
what is triglyceride range for hyperlipidemia
54-500mg/dl
what is triglyceride range for hyperlipemia
triglycerides >500mg/dl
what breeds are predisposed to hyperlipidemia/hyperlipemia
minis, pony breeds, donkeys
hyperlipidemia/hyperlipemia is a condition characterized by atypical __
VLDLs
horses with hyperlipidemia/ hyperlipemia have a apolipoprotein __ instead of __
apoB-48, apoB-100
what is a major consequence of hyperlipidemia/ hyperlipemia
hepatic lipidosis
how can you prevent hyperlipidemia/ hyperlipemia
monitor triglycerides in high risk patients, appropriate nutrition
what is tx for hyperlipidemia/ hyperlipemia
- Enteral feeding with NG tube, small frequent feedings, IV dextrose
- Parenteral nutrition- dextrose and amino acids
- Monitor glucose frequently
do not use __ in parenteral nutrition formula
lipid fraction
pheochromocytoma is neoplasia of __
adrenal gland
how do horses with pheochromocytoma typically present
hemoabdomen
what are some signs of pheochromocytoma
- Increased catecholamines
- Tachycardia
- Weight loss
how do you dx pheochromocytoma
Urinary catecholamines
Inappropriate lactation is most often secondary to __
PPID
__ in forage can cause inappropriate lactation
phytoestrogens
how do you tx inappropriate lactation
- Pergolide
- Dietary modification- grass hay, no grain
what are some differentials for increase Ca2+ in horses
- Chronic renal failure
- Neoplasia- lymphoma—> increase PTHrP
- Vitamin D toxicity
- Primary hyperparathyroidism
how do you know if increase ca2+ is related to chronic renal failure
Issues with creatinine
if you have increase Ca2+ in horse and thickened colon wall on ultrasound what is presumptive dx
lymphoma
what are some differentials for decreased Ca2+
- Blister beetle toxicosis
- Exercise induced exhaustion
- Sepsis
- Lactation
- Acute renal failure
- Primary hypoparathyroidism
what other sign besides decreased Ca2+ in blister beetle toxicosis is supportive
urine positive for cantharidin
what other bloodwork sign besides decreased Ca2+ supports acute renal failure
Mg2+ low
if you have a horses with recent history of weight loss. What questions do you need to ask
- Is horse eating and losing weight vs loss of appetite
- Determine muscle wasting vs weight loss vs both
Case: 18yr old horse presents with recent hx of weight loss, bloodwork shows hypercalcemia- what is likely dx
neoplasia- increase PTHrp
case ex: 6yr Arabian competed in 50 mile endurance race in Oklahoma yesterday. Colicky signs early this morning. Bloodwork shows hypocalcemia- what is likely dx
canthardin- blister beetle toxicosis
if you have a male jack donkey breed with female mare what offspring do you get
mule
if you bred a stallion horse with Jenny donkey what do you get
hinny
what is normal TPR for donkeys
T= 98.8 (97.2-100.0)
P= 44 (36-68)
R 12-20; 13-31
t or f: donkeys are more prone to obesity than horses
true
t or f: crest fat may be insignificant
true
In Obese donkeys what do you need to be cautious about with IM vaccines/drugs
avoid IF injections
describe the hoof anatomy of donkeys/mules
“U” shaped foot, more upright wall, thicker sole and walls, P3 not aligned with dorsal wall
t or f: elevate heel in laminitis donkeys
false
what is a significant hematology finding in donkeys/mules vs horses
signifiant dehydration (12-15%) may occur before PCV increases
what is the serum color in donkeys/mules compared to horses
lighter than horses (horses more icteric)
t or f: creatinine, total bilirubin higher in donkeys/mules
false- lower
t or f: creatinine kinase, GGT, and alkaline phosphate higher in donkeys
true
T or f: insulin is lower in donkeys/mules and ACTH is higher
true
what dx should be on your differential list with any sick donkey
hyperlipemia
what can cause hyperlipemia
decrease feed intake for any reason, increase feed requirement
sick donkey presents- pull blood and this is what serum looks like- what is wrong
Hyperlipemia
what is triglyceride value for hyperlipemia in donkeys. What normal
> 500mg/dl (normal <200mg/dl)
what is prognosis for hypothermia in donkeys
poor prognosis, 80% mortality
what Is potentially involved in hypothermia in donkeys
thyroid
what are common locations for colic in donkeys
pelvic flexure, cecum
parasitism in donkeys can result in ___
rectal prolapse
how does excretion of flunixin meglumine, phenylbutazone, and trimethoprim sulfamethoxazole differ in donkeys vs horses/mules
cleared much faster
donkeys and mules require __dose of alpha 2 agonists
higher
t or f: donkeys are more sensitive to guiafenesin
true
t or f: ketamine is cleared more slowly in donkeys
false
what is answer and what is likely cause of 2/6 heart murmur in this horse
C. Endogenous ACTH and FEC
2/6 HM- aortic regurgitation
what answer
C. Serum triglycerides