Dihydrotestosterone

Dihydrotestosterone (DHT) is a biologically active metabolite of the hormone testosterone, formed primarily in the prostate gland, testes, hair follicles , and adrenal glands by the enzyme 5α-reductase by means of reducing the 4,5 double-bond. Dihydrotestosterone belongs to the class of compounds called androgens, also commonly called androgenic hormones or testoids. Androgens are part of the biology of gender by stimulating and controlling the development and maintenance of masculine characteristics. DHT is 3 times more potent than testosterone; testosterone is 5-10 times more potent than adrenal androgens.

The main androgen secreted by the testes is of course testosterone. However, in most of the body, the androgenic signal is not carried through by testosterone. In these tissues, which include the brain (CNS), skin, genitals – practically everything but muscle – the active androgen is actually DHT. Testosterone in this case simply acts as a prohormone that is converted to the active androgen DHT by the action of the enzyme 5-AR. 5-AR is concentrated heavily in practically every androgen dependent area of the body except for skeletal muscle which results in very little testosterone actually getting through to these parts of the body to bind to androgen receptors. Instead, it is quickly transformed into DHT, which then interacts with receptors.This transformation serves a very important biological function in these tissues. You see, DHT is a much stronger androgen than testosterone – it binds about 3-5 times more strongly to the androgen receptor. If you took away 5-AR from these tissues and blocked the formation of DHT, then you would see some dramatic changes in physiology. DHT can also be used as an anti-estrogen. It works to do this through three different methods. First, DHT directly inhibits estrogens activity on tissues. It either does this by acting as a competitive antagonist to the estrogen receptor or by decreasing estrogen-induced RNA transcription at a point subsequent to estrogen receptor binding. Second of all, DHT and its metabolites have been shown to directly block the production of estrogens from androgens by inhibiting the activity of the aromatase enzyme. The studies done in breast tissue showed that DHT, androsterone, and 5alpha-androstandione are potent inhibitors of the formation of estrone from androstenedione. 5alpha-androstandione was shown to be the most potent, while androsterone was the least. Third, DHT acts on the hypothalamus / pituitary to decrease the secretion of gonadotropins. By decreasing the secretion of gonadotropins you decrease the production of the raw materials for estrogen production – testosterone and androstenedione (DHT itself cannot aromatize into estrogens).