Where in the body of a brown layer is the hormone calcitonin synthesized, and where does it act to prevent excessive blood calcium levels?

Calcium homeostasis in laying hens is a complex endocrine process. When blood calcium levels rise above the physiological norm (hypercalcemia), typically after intensive intestinal absorption of dietary limestone, the hormone Calcitonin is released. This hormone is synthesized and secreted by the C-cells of the Ultimobranchial glands, a pair of small, endocrine structures located in the neck region, posterior to the thyroid and parathyroid glands. Calcitonin acts as a biological counter-regulator to parathyroid hormone (PTH). It acts on the skeletal system, stimulating osteoblast cells to deposit excess calcium back into the medullary bone depots, while inhibiting osteoclasts. Simultaneously, it acts on the renal tubules of the kidneys, promoting the excretion of excess calcium in urine to protect the kidneys from urolithiasis. Farmers can read about avian endocrinology in the Poultry Encyclopedia, purchase organic trace minerals on Poultry Plaza, monitor daily egg rates on Poultry Rates, and list strong-shelled flocks on Murghi Mandi.