What is the best screening test for canine hyperadrenocorticism (Cushing's disease)?

The low-dose dexamethasone suppression (LDDS) test is the preferred screening test for canine hyperadrenocorticism. Collect baseline cortisol, administer 0.01 mg/kg dexamethasone IV, then collect cortisol at 4 hours and 8 hours. Normal dogs suppress below 1.4 mcg/dL at 8 hours. The ACTH stimulation test is the gold standard for monitoring treatment with trilostane or mitotane.

How do you distinguish PDH from an adrenal tumor on the LDDS test?

On the LDDS test, PDH (pituitary-dependent hyperadrenocorticism) typically shows suppression at the 4-hour or 8-hour sample (cortisol falls below 50% of baseline or below 1.4 mcg/dL). An adrenal tumor (AT) shows no suppression at either time point. The high-dose dexamethasone suppression (HDDS) test using 0.1 mg/kg can further differentiate PDH (suppresses) from AT (does not suppress).

What electrolyte pattern is classic for typical Addison's disease?

Typical Addison's disease (hypoadrenocorticism) causes loss of both mineralocorticoids and glucocorticoids, resulting in hyponatremia and hyperkalemia. The sodium-to-potassium (Na:K) ratio falls below 27 (normal is 27-40). Atypical Addison's involves glucocorticoid deficiency only, so electrolytes remain normal.

Which insulin is preferred for diabetic cats, and why?

Glargine (Lantus) or protamine zinc insulin (PZI) are preferred for diabetic cats because cats require a longer-acting, peakless or flat-profile insulin. NPH insulin has too short a duration of action in cats. Cats fed a low-carbohydrate canned diet combined with glargine or PZI achieve diabetic remission in approximately 50% of cases within 6 months.

What is the pathognomonic sign of PPID (equine Cushing's disease)?

Hypertrichosis — a long, curly, often wavy coat that fails to shed normally — is pathognomonic for pituitary pars intermedia dysfunction (PPID) in horses. Other signs include weight loss, muscle wasting, laminitis, polyuria/polydipsia, and hyperhidrosis. Diagnosis is confirmed by elevated resting plasma ACTH, interpreted against seasonal reference ranges.

How is feline hyperthyroidism treated, and what renal concern must you monitor?

Feline hyperthyroidism is treated with methimazole (or carbimazole), radioactive iodine (I-131, which is curative), surgical thyroidectomy, or iodine-restricted Y/D diet. A critical concern is masked renal disease: hyperthyroidism increases cardiac output and GFR, maintaining creatinine in the normal range despite underlying chronic kidney disease. Treatment must be introduced gradually, with renal values rechecked 4 weeks after starting therapy.

NAVLE exam-prep

NAVLE Endocrinology High-Yield Guide: Hormonal Disease Questions Decoded

May 4, 2026 5 min read 130 views

Master NAVLE endocrinology: Cushing's, Addison's, hypothyroidism, hyperthyroidism, diabetes mellitus, PPID, EMS, and milk fever — diagnostic tests and first-line drugs.

Endocrinology questions are among the most consistently tested topics on the NAVLE. Cushing's disease, Addison's disease, hypothyroidism, hyperthyroidism, and diabetes mellitus appear on virtually every exam cycle, as do equine PPID and bovine metabolic disease. These cases reward candidates who have mastered the diagnostic algorithm and know the first-line drug cold. This guide organizes the high-yield clinical information you need — species by species, disease by disease — so you can answer NAVLE endocrinology questions with confidence.

For a broader framework of how endocrinology fits into the full exam, see the NAVLE Exam Complete Guide.

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