Biomedical cell biology: Estrogen

Skin and hormones: repair highly regulated by sex steroid hormones mediated through intracellular nuclear recptors

activation of the nuclear receptors either induces or represses the downstream target genes

sex steroid hormones are synthesised from cholesterol through a series of enzymatic reactions 

eostrogens, progestogens and androgens

circulating levels are synthesised in the gonads (ovaries or testes) and adrenals

active sex steroid hormones are synthesised locally in peripheral tissues (skin, adipose, muscle, bine, liver , kidney) mainly due to the peripheral formation of sex-steroid hormones from inactive adrenal derived precursors. Some evidence of synthesis in epidermis/sebaceous glands

in men 30-50% of androgens and all most all estrogens ae produced in peripheral tissues

in premenopausal women 75% of active eostrogens and almost all androgens are made in peripheral tissues (in postmeno almost all in peripheral for both)

inactive adrenal derived precursors include dehydroepiandrosterone (DHEA) DHEA sulphate (DHEA S) and androstenedione (4 dione)

peak of steroid pre cursors occurs between 20 and 30 then declines sharply resulting in a dramatic fall in peripheral steroid hormone function

estrogens

circulating: made in the ovaries and placenta in premeno women. in males small amount produced in testes

active: adrenals. both sexes

postmeno circulating levels fall rapidly

both sexes produce a substancial amount from adrenal derived precursors during youth

peripheral production of estrogen declines in both genders with age due to decline in adrenal derived precursors

three main endogenous estrogens: estradiol, estrone and estrio

estradiol most potent in terms of biological activity 

estrogens generally bind to nuclear receptors inside cellsand induce or repress transcription of target genes. 2 types of receptors ER alpha and ER beta

effects of estrogen on skin

increases mitotic rate of epidermal cellsthus improving skin thickness and barrier function

reduces…