Which of the gland secretes calcitonin for regulation of calcium metabolism?: (A) Thyroid gland, (B) Parathyroid gland, (C) Both of the above, (D) None of the above
Answer is A. Calcitonin is produced by the parafollicular cells of the thyroid gland, which are also known as the clear or C cells. Its secretion is increased when the thyroid gland is exposed to a plasma calcium level of approximately 9.5 mg/dL. The actions of calcitonin are sho-lived because it has a half-life of less than 10 min in humans. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 21. Hormonal Control of Calcium & Phosphate Metabolism & the Physiology of Bone. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.