Parathyroid and ultimobranchial glands: Calcium metabolism in birds
Calcium is essential for normal metabolic processes in birds. Several hormonal systems exist to regulate calcium levels. These include calcitonin from the ultimobranchial glands, parathyroid hormone from parathyroid tissue, vitamin D, and the reproductive hormones, especially estrogens. These systems interact closely to keep plasma and tissue calcium levels at a steady state. Calcium disorders may be caused by a number of factors, and can lead to a variety of clinical problems in pet birds. The physiology of calcium metabolism in avian species is discussed along with common disease states arising from derangements in calcium homeostasis.