Cushing's disease in dogs is caused by excess production of which hormone?

• A. Insulin
• B. Thyroxine
• C. Cortisol
• D. Growth hormone

Answer: (C)

Cushing's disease in dogs is caused by excess cortisol. Cortisol is a glucocorticoid hormone produced by the adrenal glands under the control of ACTH from the pituitary. When cortisol stays high over time, it disrupts metabolism and tissue function, leading to signs like increased thirst and urination, a pot-bellied appearance, hair thinning, and panting. The excess cortisol can come from a pituitary tumor producing too much ACTH or from an adrenal tumor secreting cortisol directly.

The other hormones listed don’t explain Cushing's: insulin lowers blood sugar and isn’t linked to this condition; thyroxine controls metabolic rate and excess thyroxine causes hyperthyroidism rather than Cushing’s; growth hormone affects growth and metabolism but is not the cause of Cushing’s disease.