Calcitonin secretion in lizards is primarily attributed to which anatomical structure?

The secretion of calcitonin in lizards is primarily associated with the ultimobranchial bodies. These anatomical structures are specialized organs that arise from branchial tissue and are found in the pharyngeal region of lizards and some other reptiles. They play a crucial role in the regulation of calcium homeostasis in conjunction with other endocrine glands.

Calcitonin itself is a hormone responsible for lowering blood calcium levels by inhibiting osteoclast activity in bones and reducing renal tubular reabsorption of calcium. In lizards, while the thyroid gland is primarily known for producing thyroxine, calcitonin is specifically secreted by the ultimobranchial bodies, which makes them the main contributors to the production of this hormone in these reptiles.

This understanding emphasizes the unique adaptations in lizard anatomy and physiology that facilitate their regulatory mechanisms, distinguishing them from other vertebrates where calcitonin may primarily be produced in the thyroid gland.