Hypothalamic and pituitary function

Abstract 

The endocrine system consists of groups of cells (glands) that secrete messengers (hormones), which affect distant groups of cells (target organs). It controls mainly basal processes. Hormonal action may be on receptors in the target cell membrane (e.g. leading to alterations in membrane channel properties), in which case it is rapid, or it may affect gene function and thus protein synthesis, in which case the onset of action is relatively slow. Endocrine function is controlled via single and multiple feedback mechanisms from products of the various target organs. It is largely under the control of the hypothalamus via the pituitary gland. Releasing factors and hormones from the hypothalamus act on the pituitary, which produces its own hormones (antidiuretic hormone, oxytocin, growth hormone and prolactin) as well as hormones and releasing factors that affect other endocrine glands (adrenocorticotrophic hormone, thyroid stimulating hormone, luteinizing hormone and follicle stimulating hormone). Growth hormone controls skeletal growth via the release of insulin-like growth factors from the liver; it promotes anabolism, but also antagonizes the hypoglycaemic effect of insulin. Antidiuretic hormone secretion is stimulated by changes in osmolality and is a sensitive mechanism for conserving fluid via its action on the kidney. Oxytocin stimulates uterine contraction, and prolactin stimulates milk production. Luteinizing and follicle stimulating hormones affect the growth of the gonads.

Keywords: endocrinology, feedback loops, hypothalamus, pituitary, receptors