Canine Hypothyroidism
What are the three most common IATROGENIC causes of FELINE HYPOthyroidism?
Most common – IATROGENIC
I-131 treatment
Antithyroid medications for HYPERthyroidism
Surgical thyroidectomy
What is the typical signalment for cats that are most likely to develop hyperthyroidism, in terms of age group & mean age and what is the most likely cause of hyperthyroidism in this age group?
Mainly seen in OLDER/GERIATIC CATS [mean age is 13 yrs]
CAUSE: Thyroid Adenoma
What are the four (4) hormones associated with the HPA axis.
1. Corticotropin Releasing Hormone (CRH)
2. Adrenocorticotropic Hormone (ACTH)
3. Cortisol
4. Aldosterone
What are four (4) types of Diabetes Mellitus in cats?
1. Relative Insulin Deficiency
2. Dysfunctional Beta-cells
3. Peripheral Insulin Resistance (IR)
4. Combination of Relative Deficiency & IR
What are the three (3) forms of calcium in the body?
IONIZED [biologically active form]
PROTEIN BOUND-ALBUMIN
CHELATED/COMPLEXED
State any five(5) clinicopathological features of CANINE HYPOTHYROIDISM.
Mild normocytic normochromic anaemia (up to 50% of dogs)
Increased RDW
Hypercholesterolaemia (75%)
Hypertriglyceridemia
Elevated ALP and GGT
Creatinine & SDMA (can be elevated or higher end of reference range)
Elevated fructosamine
Elevated somatotropin and IGF-1
State four (4) treatment options for feline hyperthyroidism and give examples where applicable.
Medical - methimazole
Radioactive Iodine (I-131)
Restrictive Diet (low iodine diet)
Surgical (thyroidectomy)
When using the ACTH Stimulation test, __ mcg/dL is suggestive of Addison's Disease.
If Addison's is confirmed, state a treatment drug.
Post stim: <2 mcg/dL = ADDISON’S (but not diagnostic for certain)
Post stim: >2 mcg/dL = NOT ADDISON’S
Txt Drug: Prednisone or Fludrocortisone
What is the typical signalment of DOGS and CATS presenting with Diabetes Mellitus.
DOGS: 4 to 14-year-old, female Terriers/Schnauzers/Miniature Poodles
CATS: older, neutered, male Burmese/Abyssinians/Siamese
What are four (4) causes of HYPOPARATHYROIDISM?
1. Atrophy - sudden correction of hypercalcemia
2. Iatrogenic - removal of parathyroid gland
3. Idiopathic
4. Trauma
What are two(2) drugs mentioned in the lecture that can affect thyroid hormone levels/thyroid gland function?
TMS and phenobarbitol
State one drug that can be used to treat hyperthyroidism and list any three(3) side effects of said drug.
METHIMAZOLE (Tapazole)
side effcets:
GI upset
Facial excoriation
Hepatotoxicity
Neutropenia
Renal Decomposition
What are five (5) common blood work abnormalities observed in Hypoadrenocorticism.
Hyperkalemia (Increased potassium (K⁺) concentration in the blood)
Hyponatremia (Decreased sodium (Na⁺) concentration in the blood)
Hypercalcemia (Increased calcium (Ca²⁺) concentration in the blood)
Hypoglycemia (Decreased blood glucose concentration)
Azotemia (Increased nitrogenous waste products in the blood (↑ BUN and creatinine)
What are any four (4) complications of Diabetes Mellitus?
Hypoglycemia
Insulin Resistance
Diabetic Ketoacidosis (DKA)
Diabetic Neuropathy
Cataracts
Where are CALCITONIN and Parathyroid Hormone produced
CALCITONIN: parafollicular cells (C cells) of thyroid
PTH: chief cells of the parathyroid glands
- State the name of the most common/best drug to use to treat hypothyroidism.
- State 3 potential side effects of the mentioned drug.
Drug: LEVOTHYROXINE
Side Effects: Hyperthyroidism --> PU/PD, Tachycardia & Polyphagia
List five (5) confirmatory diagnostics that be done on a suspected hyperthyroid cat.
Repeat total T4
Measure free T4
T3 Suppression Test
Nuclear Scintigraphy
TSH Measurement
What are three (3) broad treatment options for Hyperadrenocorticism.
Give a specific example of two (2) of the broad treatments mentioned.
1. MEDICAL MANAGEMENT --> Trilostane (3 beta hydroxysteroid dehydrogenase INHIBITOR) or Mitotane (Txt of choice for PDH for most cases)
2. SURGICAL MANAGEMENT --> Adrenalectomy & Pituitary Surgery (treatment of choice for A.D.H)
3. RADIATION THERAPY --> Pituitary macroadenomas
What are effects does Parathyroid Hormone have on BONE, KIDNEY & SMALL INTESTINES.
BONE - Increase resorption (release) of Ca2+ & P.
2. KIDNEY
Increase Ca2+ resorption
Increase P excretion (proximal tubules)
Stimulates synthesis of the active form of Vitamin D3 (calcitriol) via increased activity of 1-α-hydroxylase
3. SMALL INTESTINE (indirect effect)
PTH increases calcitriol which then increases Ca2+ and P absorption from intestines
What is the typical signalment of dogs with primary hyperparathyroidism (age + 1 breed) and state any two (2) common causes of PHP.
SIGNALMANET: Middle age to older, Keeshonds, Labs, Goldens, German Shepherds
CAUSES:
Parathyroid Adenoma (most common)
Parathyroid Carcinoma
Parathyroid Hyperplasia
Differentiate between tT4 and fT4 diagnostic test by Equilibrium Dialysis. (at least 3 differences)
tT4: cheaper, screening test, more affected by euthyroid sick syndrome
fT4 [more active form]: expensive, used to help confirm, less affected by illness.
NOTE: Low T4 & high TSH confirms hypothyroidism
Explain how RENAL DECOMPOSITION manifests in cats that are treated with METHIMAZOLE for hyperthyroidism.
Cats ALREADY have renal disease
Hyperthyroidism increases glomerular filtration rate (GFR) thus providing support for diseased kidneys
Txt normalizes the GFR & thus unmasks the underlying renal disease
Explain the Adrenal-Dependent Hypercortisolism Response to the Low Dose Dexamethasone Suppression Test (LDDST).
Adrenal tumor produces cortisol independent of ACTH --> excessive cortisol results in negative feedback & suppresses ACTH --> Dexamethasone will not affect adrenal production of cortisol; no suppression occurs at any timepoint ---> Cortisol levels remain high --> CUSHING'S highly likely.
A newly diagnosed diabetic cat has not yet been treated with insulin and is otherwise clinically stable. The clinician decides to use a drug that lowers blood glucose by increasing urinary glucose excretion via inhibition of sodium-glucose transport. Which of the following drugs is most appropriate?
A. Regular insulin
B. Intermediate-acting insulin
C. Gliflozin
D. Basal-bolus insulin therapy
Correct Answer: C. An SGLT2 inhibitor (gliflozin)
How would you treat a HypoPTH dog, BE SPECIFIC.
IV Calcium Gluconate supplementation (emergency) and ORAL CALCIUM (Tums)