Avian Goiter Study Guide

Overview and Clinical Importance

Avian goiter (thyroid hyperplasia or dysplasia) is an enlargement of the thyroid glands due to abnormal proliferation of follicular epithelial cells. This condition represents one of the most common endocrine disorders in pet birds and is particularly prevalent in budgerigars (where it is the most common thyroid disease), pigeons, canaries, cockatiels, and macaws (especially blue and gold macaws). Understanding this condition is essential for the NAVLE as it tests knowledge of species-specific nutritional diseases, endocrine pathophysiology, and clinical management in avian medicine.

In budgerigars, goiter has historically been one of the most common causes of death, second only to neoplasia. A study of 129 budgerigar submissions reported that approximately 24% died as a result of thyroid dysplasia attributed to iodine deficiency in seed-based diets.

Anatomy of the Avian Thyroid Gland

The avian thyroid glands are paired oval organs, dark red in color with a glistening appearance. Unlike mammals where the thyroid glands are connected by an isthmus, avian thyroid glands are completely separate bilateral structures.