Insulin effect of increasing glucose uptake and storage. Finally, insulin is degraded, terminating the response. In mammals, insulin is synthesized in the pancreas within the beta cells. One million to three million pancreatic islets form the endocrine part of the pancreas, which is primarily an exocrine gland. The endocrine portion accounts for only 2% of the total mass of the pancreas. Within the pancreatic islets, beta cells constitute 65–80% of all the cells. Insulin consists of two polypeptide chains, the A- and B- chains, linked together by disulfide bonds. It is however first synthesized as a single polypeptide called preproinsulin in
Infertility in polycystic ovary syndrome fertility, such as changed levels of gonadotropin-releasing hormone, gonadotropins (especially an increase in luteinizing hormone), hyperandrogenemia, and hyperinsulinemia. Gonadotropins are released by gonadotroph cells in pituary gland, and these cells appear to harbor insulin receptors, which are affected by elevated insulin levels. A reason that insulin sensitizers work in increasing fertility is that they lower total insulin levels in body as metabolic tissues regain sensitivity to the hormone. This reduces the overstimulation of gonadotroph cells in pituitary. PCOS usually causes infertility associated with anovulation, and therefore, the presence of ovulation indicates absence of infertility, though it does not rule out