Steroid hormones11/2/2022 ![]() ![]() Individual compounds are characterised by the presence or absence of specific functional groups (mainly hydroxy, keto(oxo) and aldehyde functions for the naturally occurring steroids) at certain positions of the carbon skeleton (particularly at positions 3,5,11,17,18,20 and 21). Steroid hormones series#Total removal produces C19-steroids of the androstane series (including the androgens), whereas loss of the 19-methyl group (usually after conversion of the A-ring to a phenolic structure, hence the term "aromatization") yields the estrane series, to which estrogens belong. Removal of part of the side-chain gives rise to C21-compounds of the pregnane series (progestins and corticosteroids). Two angular methyl groups are also found at position 18 and 19. 1a, cholesterol is made up of three hexagonal carbon rings (A,B,C) and a pentagonal carbon ring (D) to which a side-chain (carbons 20-27) is attached (at position 17 of the polycyclic hydrocarbon). ![]() ![]() The parent compound from which all steroids are derived is cholesterol. Steroid hormones: Structure, nomenclature and classification The emphasis will be on the functional and biological significance of metabolism in endocrine physiology rather than on an extensive description of the metabolic pathways and the enzymes involved. This chapter will consider both aspects of steroid metabolism. Steroid metabolism is therefore important not only for the production of these hormones, but also for the regulation of their cellular and physiological actions. This variety is not only due to the large range of compounds secreted by steroid-synthesizing tissues, but also to the fact that circulating steroids are extensively metabolised peripherally, notably in the liver, and in their target tissues, where conversion to an active form is sometimes required before they can elicit their biological responses. These neurosteroids, however, are more likely to have "autocrine" or "paracrine" functions rather than true endocrine effects.ĭespite their relatively simple chemical structure, steroids occur in a wide variety of biologically active forms. 1) that, in addition to the endocrine glands, the CNS is also able to form a number of biologically active steroids directly from cholesterol (the so-called "neurosteroids"). It has been recently discovered (review in ref. Thus, gonadal steroids influence the sexual differentiation of the genitalia and of the brain, determine secondary sexual characteristics during development and sexual maturation, contribute to the maintenance of their functional state in adulthood and control or modulate sexual behaviour. An important function of the steroid hormones is to coordinate physiological and behavioural responses for specific biological purposes, e.g. They act both on peripheral target tissues and the central nervous system (CNS). The steroid hormones are synthesized mainly by endocrine glands such as the gonads (testis and ovary), the adrenals and (during gestation) by the fetoplacental unit, and are then released into the blood circulation. ![]() Steroids are lipophilic, low-molecular weight compounds derived from cholesterol that play a number of important physiological roles. du Petit Bel-Air, 1225 Chêne-Bourg, Geneva, Switzerland Division of Clinical Psychopharmacology, University Institute of Psychiatry,Ģ, ch. ![]()
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