Avian Nutritional Secondary Hyperparathyroidism Study Guide

Overview and Clinical Importance

Nutritional Secondary Hyperparathyroidism (NSHP) is one of the most common metabolic bone diseases encountered in captive avian species. This condition results from chronic dietary calcium deficiency, vitamin D3 insufficiency, or improper calcium-to-phosphorus ratios, leading to compensatory parathyroid gland hyperactivity. NSHP is a significant cause of morbidity in pet birds, particularly those maintained on seed-based diets, and is a high-yield topic for the NAVLE examination.

The condition is especially prevalent in African grey parrots, which appear to have unique calcium metabolism requirements and may be unable to effectively mobilize skeletal calcium reserves. Understanding the pathophysiology, clinical presentation, diagnosis, and treatment of NSHP is essential for veterinary practitioners working with avian species.

Pathophysiology of Avian Calcium Metabolism

Normal Calcium Homeostasis in Birds

Calcium homeostasis in birds is regulated by a complex interplay of hormones acting on three primary target organs: the intestine, bone, and kidneys. The key regulatory hormones include parathyroid hormone (PTH), 1,25-dihydroxyvitamin D3 (calcitriol), and calcitonin. In avian species, estrogen also plays a significant role, particularly during egg production when calcium demands increase dramatically.