Hormone which is produced by the Thyroid gland as a polypeptide consisting of 32 amino acids that is used in the treatment of osteoporosis and other bone diseases and calcium metabolism.It is a natural component of breast milk as well as its predecessor, Procalcitonin, which is found in higher amount in milk than in plasma.Calcitonin levels increase during pregnancy and lactation.It has no effect on Prolactin and other Pituitary Hormones. Pharmacokinetic data (high molecular weight and rapid metabolism: Tmax and T1 / 2 short) makes it unlikely an excretion into breast milk in significant amounts. Because of a protein nature it is inactivated in the GI tract and hence not absorbed, so that their oral bioavailability is negligible, being unlikely any passage to the infant plasma, from ingested milk. An infant whose mother was treated with calcitonin every other day (plus azathioprine, warfarin, prednisone, acetaminophen, calcitriol, calcium and vitamins E and C) showed no problems after one year of lactation.