Feline Hypothyroidism Study Guide

Overview and Clinical Importance

Hypothyroidism in cats is a condition characterized by inadequate production of thyroid hormones (T4 and T3) by the thyroid gland. Unlike in dogs where primary hypothyroidism is common, feline hypothyroidism is rare as a spontaneous condition and most commonly occurs as an iatrogenic complication following treatment for hyperthyroidism. Understanding this distinction is critical for NAVLE success.

The thyroid gland produces thyroxine (T4) and triiodothyronine (T3), which regulate metabolic rate, oxygen consumption, protein synthesis, and affect virtually every organ system. Hypothyroidism results in decreased metabolic function with widespread systemic effects.

Thyroid Anatomy and Physiology

Cats have two thyroid glands (lobes) located in the ventral cervical region, lateral to the trachea at approximately the level of the 4th through 8th tracheal rings. Normal feline thyroid glands measure approximately 10-16 mm long, 3-5 mm wide, and 1-2 mm thick. Unlike dogs, the central isthmus connecting the two lobes is often vestigial or absent in cats.