Physiology of Endocrine System and Related Metabolic Disorders

Endocrine system is comprised of multiple glands. All of these glands secrete different hormones into the body. Most of the body’s functions, i.e., metabolism, growth, development, electrolyte balance, and reproduction, are regulated by these endocrine hormones. Numerous releasing and inhibitory hormones are secreted by the hypothalamus which eventually stimulates the pituitary gland’s hormonal secretions. Some of these pituitary hormones act directly on the target organs, while others act on organs situated in different regions of the body. Pituitary gland secretes growth hormone (GH), thyroid stimulating hormone (TSH), luteinizing hormone (LH), follicle stimulating hormone (FSH), adrenocorticotropic hormone (ACTH), antidiuretic hormone (ADH), prolactin, and oxytocin. Other endocrine glands include thyroid gland (secreting thyroid hormone T3 and T4, calcitonin), parathyroid gland (secreting parathyroid hormone), adrenal gland (secreting catecholamines, mineralocorticoids, glucocorticoids, androgens, and cortisol), pancreas (secreting insulin and glucagon), gonads (secreting sex hormones), pineal gland (secreting melatonin), and thymus gland (secreting thymosin hormone). Most of the endocrine hormones are regulated by negative feedback mechanism. There are many metabolic disorders associated with the over and under production of all these hormonal secretions by different glands. In this chapter along with describing endocrine gland’s physiology, we have discussed in detail all the associated endocrine metabolic disorders, i.e., hyperthyroidism, hypothyroidism, iodine deficiency, hypoparathyroidism, adrenal insufficiency, Cushing’s syndrome, acromegaly, galactorrhea, erectile dysfunction, central diabetes insipidus, hypopituitarism, pituitary apoplexy, diabetes mellitus, hypoglycemia, diabetic ketoacidosis, hyperosmolar hyperglycemic nonketotic coma.