Chemical Coordination And Integration

Calcitonin is a -amino acid linear polypeptide hormone that is produced in humans primarily by the parafollicular cells (also known as -cells) of the thyroid and in many other animals in the ultimobranchial body. It acts to reduce blood calcium , opposing the effects of parathyroid hormone . It has been found in fish, reptiles, birds, and mammals. Its importance in humans has not been as well established as its importance in other animals, as its function is usually not significant in the regulation of normal calcium homeostasis.

GnRH stimulates the synthesis and secretion of the two gonadotropins?luteinizing hormone (LH) and follicle-stimulating hormone (FSH)?by the anterior pituitary gland. In order to increase serum gonadotropin concentrations in patients with GnRH deficiency, the releasing hormone must be administered in pulses.

Progesterone is secreted by corpus luteum and also by placenta at later stages. It brings about most of the pregnancy changes such as development of uterine lining and mammary gland, formation of placenta and also maintains pregnancy.