Endocrine Flashcards
Percentage of lymphocytic thyroiditis?
> 50 %
Percentage TGAA?
T4?
T3?
50 %
15 %
30 %
What breeds predisposed TGAA?
Beagle, borzoi (inherited)
GRet, Gt Dane, Irish setter, Doberman, OES
What ECG changes hypothyroidism?
Bradycardia, low QRS voltage, low P wave amplitude, inverted T waves
1st/2nd degree AV block
How many TGAA pos dogs get decreased T4/signs hypothyroidism in a year?
20 % decreased T4, 5 % signs, 15 % TGAA negative
What mutations cause congenital hypothyroidism? What breeds?
Genetic tests?
Nonsense TPO mutation, autosomal recessive, toy fox and rat terriers
Missense TPO mutation, autosomal recessive, Tenterfield terrier
Genetic tests available for both. Both goitre.
Also Spanish water dog/papillon
Sensitivity and specificity of T4?
89 - 100/73 - 82
T3?
10/poor
Free T4?
80 - 98/93-94 most accurate
TSH?
58-87/82-100
Normal up to 30 % hT4 dogs
TGAA?
91-100/94-100
T4 + TSH?
63 - 67/98-100
FT4 + TSH
74/98
What breeds have decreased T4?
Greyhound, Basenji, Sloughi, Saluki, Whippet
Small number Scottish deerhound, dogue de Bordeaux and giant schnauzer
Decreased T3?
Saluki, Irish Wolfhound
NORMAL in greyhounds
Decreased free t4?
Greyhound, Sloughi, Saluki, Irish wolfhound
NORMAL whippet
What changes T4 to T3?
5’deiodinase
What happens to TSH and GH after TRH stim in hT4 dogs?
Increase GH more and TSH less than healthy
Why are human thyroid supplements inappropriate for dogs?
Too much T3
When should thyroid supplementation starting dose be decreased?
Underlying heart disease, decrease 25 - 50 %
What drugs decrease T4?
cTSH?
Free T4?
T4 - Prednisolone, phenobarbital, TMPS, aspirin, clomipramine
cTSH - prednisolone, phenobarbital (may also increase)
TMPS increases TSH
FT4 - prednisolone, phenobarbital, TMPS, aspirin, clomipramine
No effect on anything - NSAIDs (ketoprofen decrease T4?), propranolol, KBr
What is Schmidt’s syndrome?
Polyglandular endocrinopathy type 2 - hypoadrenocorticism with hT4 and/or DM
Skin histopathology hT4?
Telogen preedominance, dermal thickening, erector pili vacuolation
UNCOMMON - atrophic/dystrophic follicles
Myopathy in hypothyroidism?
Increased T1 decreased T2 fibres, nemaline rod inclusion, myofiber degeneration
When will congenital hT4 be apparent by?
8w
Mechanism bradycardia hT4?
Decreased beta receptor number/function
Decreased sarcolemmal ATPase
Decreased Na K ATPase
Mechanism hyponatraemia hT4?
Aldosterone pumps require T4
Renal effects of hyperthyroidism?
Decreased TPR, decreased effective arterial filling volume, stimulation RAAS.
Sodium absorption, increased plasma volume, increased CO.
Increased chloride resorption PCT, increased tubuloglomerular feedback as decreased tubular chloride - inc GFR.
Impaired renal natriuretic peptide response.
Increased glomerular capillary hydrostatic pressure.
Increased plasma volume and decreased sodium excretion.
Increased tubular phosphate absorption.
Downregulate aquaporin, increase Na/K ATPase
Bilateral disease hyperthyroid cats?
> 66 %
Possible mechanisms for hyperthyroid renal injury?
Hyperphosphataemia, glomerular hyperfiltration, proteinuria
Ectopic thyroid tissue in hyperthyroidism?
4 - 20 %
Risk factors for hyperthyroidism
Non pure breed, canned food, cat litter, flea control, long hair, female
Tachycardia in hyperthyroidism?
Thyroid hormone positive chronotrope, increase myocardial beta receptors, decrease AV conduction time, positive inotrope
Predictors of azotaemia post-I131?
GFR, SDMA
NOT proteinuria, creatinine, USG, cystatin C
T/F: Cats with hyperthyroidism have a higher prevalence of subclinical bacteriuria
False
Cystatin C in HT4?
Increased in serum versus FIV cats and increased in urine versus healthy cats
No difference azotaemic and didn’t change with treatment
T4/TSH association with mortality in cats?
Decreased predicts 30 d mortality
How much feline TSH does canine assay detect?
40 %
Sensitivity T4/free T4 for HT4?
91/98
fT4 low specificity - increased 12 % NTI
Side effects thyroperoxidase inhibitors?
GI upset (less transdermal methimazole), hepatopathy (necrosis/degeneration/glutathione depletion), bleeding diathesis (inh vit K epoxide reductase?), cytopenia, facial excoriation, myasthenia graves
Negative prognostic indictors HT4 cat?
Azotaemic pre-treatment (NOT POST) Hypothyroid and azotaemic after therapy Older Hypertensive Proteinuric Male Methimazole vs I131 tx
Post-I131 hypothyroidism?
Usually return to normal 3 months.
Increased risk hypothyroidism if bilateral/previous medical management/medical management close to I131
5 - 83 % depending on classification
57 % azotaemic (more than euthyroid) - will resolve azotaemia in 50 % if supplement
TSH most specific and sens.
Efficacy methimazole?
90 % if use BID, 54 % SID
Post-treatment azotaemia prevalence?
15 - 20 %
Methimazole effect on technetium scanning?
None - no effect iodine uptake
Association between methimazole and I131 efficacy?
None
Beta blockers in HT4?
Decrease T4 - T3 conversion
Propanolol non-selective (bronchospasm)
Atenolol B1 selective
Half life of radio iodine?
8 days
Can you use Y/D in cats with renal disease?
Might be ok - controlled phosphorous and sodium, high quality protein, supplemented with omega 3
Response to diet HT4?
90 % euthyroid
Mechanism of action of I131?
Beta particles damage hyper functional thyroid tissue (80 %) - gamma other 20 %
Most sensitive diagnostic for hyperthyroidism?
Pertechnate scan
Levothyroxine dosing hypothyroid cats?
Twice daily, short T4 half life
Lipid changes in canine hypothyroidism?
Increased cholesterol/triglyceride (75 %), decreased LDL receptors, decreased cholesterol-rich LDL entry into liver for clearance
Altered initial management of concurrent hypothyroidism and DM?
Slow intro levothyroxine 25 % dose at first as insulin requirements will decrease (improvement of receptor and post receptor factors)
Insulin action on adipocytes?
Inhibit hormone sensitive lipase and stimulates lipoprotein lipase
Glargine insulin characteristics?
Asparagine replaced with glycine, two arginine additions.
Microprecipitates at neutral pH, soluble pH 4
Detemir characteristics?
Myristic acid replaces threonine
Binds to albumin to prolong metabolism
Factors increasing/decreasing fructosamine?
Increase: hyperproteinaemia, hypothyroidism.
Decrease: azotaemia, haemolysis, hyperlipidemia, hyperthyroidism
DoA insulin dog?
Lente 8 - 14 NPH 4 - 10 PZI 10 - 16 Glargine 8 - 16 Detemir 8 - 16 - much more potent
Number of HAC dogs with DM?
8 %, 40 % increase glucose
UTI prevalence in canine DM?
50 %
Histopath diabetic neuropathy?
Segmental demyelination, axonal degeneration
Diabetic renal changes in dogs?
Membranous glomerulonephropathy
Increased UPCR/albuminuria in 50 %
Factors impacting PBGM
Haematocrit, hypotension, hypoxia, triglycerides
Factors increasing the probability of DM remission in cats?
Protocol, shorter time since diagnosis, steroid administration, high protein low carb diet, longer acting insulins, tight control, older animal.
Less likely - plantigrade stance, increased insulin dose for glycemic control, increased cholesterol
GH and IGF1 effects?
GH catabolic - insulin resistance, carbohydrate intolerance, hyperglycaemia, DM
IGF-1 - anabolic
Risk factors feline DM?
Male, Burmese (incomplete penetrant autosomal dominant), obesity, diabetogenic drugs, high fat/high carb diet, Maine Coone, Russian blue, Siamese
What polymorphism do obese cats with DM have?
Melanocortin 4 receptor
Mechanisms of beta cell toxicity feline DM?
Misfolded amyloid deposition and cytokine infiltration.
ROS generation and apoptosis.
ER stress, misfolded protein, apoptosis.
Hexosamine biosynthetic pathway and glucose flux
Overabundant nutrient supply (glucolipotoxicity)
Advanced glucosylation end products
Inflammation
Dedifferentiation and death
How many cats are in DKA at DM diagnosis?
12 - 37 %
How many DM cats have hypersomatotropism?
25 - 30 %
SDMA in feline DM?
Decreased cf healthy cats
Risk factors for relapse after DM remission in cats?
30 - 80 % remission, 25 - 30 % relapse, < 25 % second remission
Impaired fasting glucose/impaired glucose tolerance, obesity, use of steroids.
Why might lente insulin have a very short duration of action in cats?
Shorter duration of action anyway, glucose very high, rapid drop, counter-reg hormones (glucagon cortisol epinephrine)
When should insulin be stopped in a cat with DM?
Preinsulin blood glucose consistently < 10, nadir 4 - 7 and 0.5 IU once daily for two weeks
Mechanism of action of glipizide? Drug class? DM cat response?
Stimulates potassium channel on beta cell therefore increases insulin secretion
Sulfonylurea
< 20 % remission, improvement 30 %
Acarbose DM?
Inhibit brush border disacharidase
Alpha glucosidase inhibitor
Similar to low carb diet for glucose lowering post prandial but only if 1/2 meals per day
Risk of CKD in DM cats?
44 % (versus 11 % without DM)
UTI in DM cats?
12 - 13%
Renal changes DM cats?
50 % glomerular changes, 33 % tubulointerstitial, 70 % increase UPCR/albuminuria
Negative prognostic indicators for feline DKA?
Azotaemia, hyperbilirubinemia
Changes in IGF1 in DM cats?
IGF1 predicts remission (increased) at 2w. Ternary complex (acid labile complex) and IGFB3 increased in cats achieving remission.
Lispro versus soluble insulin for feline DKA?
One study found quicker time to BG <13, other no diff.
Carbohydrate content for DM cats?
< 12 %
Mechanism/drug class/response nateglinide?
Stim potassium channel beta cells (different site cf sulfonylureas)
Meglitinide
Faster action/shorter duration cf sulfonylurea, renal excretion
Metformin?
Insulin sensitiser
Biguanide
One case report good glycemic control
Chromium/vandium
Chromium = insulin function cofactor
Vandium glycemic control, bypass insulin receptor to activate glucose metabolism in the cell - can help with receptor problems
Trace elements
Chromium increase glucose tolerance, vandium improved clin signs, PZI req, BG and fructosamine
Frequency of hypoglycaemia/rebound hyperglycaemia?
Common hypoglycaemia with 25 % rebound hyperglycaemia, however insulin resistance rare. No diff PZI/glargine
DoA insulin cat?
Lente 8 - 10 (nadir 3 - 6)
PZI 9 - 24 (nadir biphasic 1st 5 - 7)
Glargine 6 - 24 (nadir 10 - 24)
Detemir 9 - 14, more potent
Mechanism exenatide?
GLP1 agonist - remission 40 % good control 89 % cats DM versus placebo, no weight gain, decreased glycemic variability
PZI versus lente cat?
Longer duration of action, transition from lente better QoL and control
When is IGF-1 produced?
GH stimulation, in the liver, with sufficient portal insulin concentrations
Cause of feline hypersomatoptropism?
Pituitary acidophil adenoma or acidophil hyperplasia (latter = minority). Anterior pituitary.
Some produce other pituitary hormones.
Cause - organohalogenated contaminants eg polybrominated diphenyl ethers. AIP protein mutation.
Sex bias feline hypersomatoropism?
Male
Breed bias?
DSH
Phosphate in hypersomatotropism?
Increased - increased tubular absorption
T/F - hypersomatotopism and DM cats have increased prevalence azotaemia
False
GH sens/spec for hypersomatotropism?
> 10 84/95 - feline assay
Above RI 100 %
Prevalence CNS signs hypersomatotropism?
10 - 15 %
What does IGF1 do to somatostatin?
Increases - which inhibits insulin release
IGF-1 performance for feline hypersomatotropism?
84 - 100 % sens, 88 - 92 % spec. PPV 95 %.
False neg untreated DM, malnutrition, hepatic/renal failure, hypothyroidism
Decreases after hypophysectomy and pasireotide, not XRT