Endocrine system

organs. Endocrine glands secrete their products immediately into the blood or interstitial fluid, without storage of the chemical. Hormones act as "messengers," and are carried by the bloodstream to different cells in the body, which interpret these messages and act on them. Typical endocrine glands are pituitary, thyroid, and adrenal glands, but not exocrine glands such as salivary glands, sweat glands and glands within the gastrointestinal tract. The field of medicine that deals with disorders of endocrine glands is endocrinology, a branch of the wider field of internal medicine.

Physiology

The endocrine system provides a chemical connection from the hypothalamus of the brain to all the organs that control body metabolism, growth and development, and reproduction. There are two types of hormones secreted in the endocrine system: (1) steroidal and (2) nonsteroidal, or protein based, hormones. Signal transduction of some hormones with steroid structure involves nuclear hormone receptor proteins that are a class of ligand activated proteins that, when bound to specific sequences of DNA serve as on-off switches for transcription within the cell nucleus. These switches control the development and differentiation of skin, bone and behavioral centers in the brain, as well as the continual regulation of reproductive tissues. They also bind to receptor sites, and activate second messenger systems for more rapid responses. Nonsteriodal hormones bind to receptor sites on the external surface of the cell membrane and use a second messenger method of altering internal cell functions, by altering the pathways already existing in the cells, by activating or deactivating enzymes which modify existing proteins. The endocrine system regulates its hormones through negative feedback control. Increases in hormone activity decreases the production of that hormone. The immune system and other factors contribute as control factors also, maintaining constant levels of hormones. Reference: http://www.hormoneprofile.com/howhormoneswork.htm

Endocrine glands and the hormones secreted

*Hypothalamus produces **Thyrotropin-releasing hormone (TRH) **Gonadotropin-releasing hormone (GnRH) **Growth hormone-releasing hormone (GHRH) **Corticotropin-releasing hormone (CRH) **Somatostatin (SS; also GHIH, growth factor-inhibiting hormone) **Dopamine (DA) *Pineal Gland produces **Melatonin *Pituitary gland (hypophysis) produces **Anterior pituitary lobe (adenohypophysis) ***Growth hormone (GH) ***Prolactin (PRL) ***Adrenocorticotropic hormone (ACTH, corticotropin) ***Thyroid-stimulating hormone (TSH, thyrotropin) ***Follicle-stimulating hormone (FSH, a gonadotropin) ***Luteinizing hormone (LH, a gonadotropin) **Posterior pituitary lobe (neurohypophysis) ***Oxytocin (ocytocin) ***Arginine vasopressin (AVP; also ADH, antidiuretic hormone) ***Lipotropin *Thyroid gland produces **Triiodothyronine (T3), the potent form of thyroid hormone **Thyroxine (T4), a less active form of thyroid hormone **Calcitonin *Parathyroid gland produces **Parathyroid hormone (PTH) *Heart produces **Atrial-natriuretic peptide (ANP) *Stomach and intestines produce **Cholecystokinin (CCK) **Gastrin **Ghrelin **Neuropeptide Y (NPY) **Secretin **Somatostatin *Liver produces **Insulin-like growth factor (IGF) **Angiotensinogen **Thrombopoietin *Islets of Langerhans in the pancreas produce **Insulin **Glucagon **Somatostatin *Adrenal glands produce **Adrenal cortex ***Glucocorticoids (chiefly cortisol) ***Mineralocorticoids (chiefly aldosterone) ***Androgens (including DHEA and testosterone) **Adrenal medulla ***Adrenaline (epinephrine) ***Noradrenaline (norepinephrine) **Testosterone *Kidney produces **Renin **Erythropoietin (EPO) **Calcitriol (the active form of vitamin D₃) *Skin produces **Vitamin D₃ (calciferol) *Adipose tissue **Leptin **Estrogens (mainly estrone)

In males only

*Testes **Androgen