21.13: Synthesis and Functions of Calcitonin
Calcitonin, a vital polypeptide hormone, regulates calcium levels within body fluids. It is released by the parafollicular cells, also known as C cells, situated in the follicular epithelium of the thyroid gland. Calcitonin responds to fluctuations in blood calcium levels and the influence of gastrointestinal hormones like gastrin and cholecystokinin.
The exact mechanisms by which calcitonin operates in calcium homeostasis remain elusive, but its significance is evident in several vital functions. Notably, calcitonin is crucial in bone calcium storage, particularly during childhood, stimulating bone growth and mineral deposition. Additionally, calcitonin prevents bone mass loss in adults, especially in prolonged starvation and later stages of pregnancy.
Calcitonin's impact extends to the digestive system, which participates in calcium ion absorption. Additionally, it exerts a regulatory influence on post-meal calcium surges by promoting calcium excretion through the kidneys.
The intricate involvement of calcitonin in calcium regulation underscores its dual role in maintaining skeletal integrity and contributing to overall calcium homeostasis. This hormone regulates calcium balance in the body throughout different life stages and physiological conditions.
