What hormone is primarily produced by parafollicular C cells in medullary thyroid cancer?

Parafollicular C cells, also known as C cells, are located within the thyroid gland and are responsible for the production of calcitonin. Medullary thyroid cancer originates from these C cells, leading to an overproduction of calcitonin. Calcitonin plays a role in regulating calcium levels in the blood by inhibiting osteoclast activity and reducing calcium release from bones, as well as decreasing renal tubular reabsorption of calcium, which can ultimately lead to lower blood calcium levels.

The other hormones listed are produced by different glands or cell types. Thyroxine, also known as T4, is primarily produced by the follicular cells of the thyroid gland and is involved in regulating metabolism. Parathyroid hormone is produced by the parathyroid glands and increases blood calcium levels by acting on bones, kidneys, and the intestine. Cortisol is a steroid hormone produced by the adrenal cortex, playing a vital role in metabolism, immune response, and stress response. None of these hormones are produced by parafollicular C cells, highlighting the specific role of calcitonin in medullary thyroid cancer.