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THE ROLE OF ANDROGENS

Androgens are steroid molecules synthesized from cholesterol. In normal females, they are produced in the ovaries, in the suprarenal gland and in tissues capable of performing a peripheral conversion, such as adipose, hepatic and mammary tissue.
The three male hormones with masculinization capacity, listed in order from lesser to greater activity are: DHEA (DEHYDROEPIANDROSTERONE, ANDROSTENEDIONE AND TESTOSTERONE). The ovaries synthesize more androstenedione, the suprarenal gland more DHEA and testosterone is produced in both.

In blood, hormones travel free (active form) in a minimum quantity. Most bind with a transporter protein called SVG and with albumin.

DHEA (dehydroepiandrostenedione), androstenedione and testosterone penetrate the hair follicle and transform into an active hormone called dehydrotestosterone by the mediation of a very important enzyme called alpha-reductase, which is also involved in androgenetic alopecia. Dehydrotestosterone binds with a membrane receptor and reaches the nucleus stimulating the production of RNA, which in turn will order protein synthesis. The hair follicle will develop and vellus hair will become terminal hair.

The armpit and pubic area hair developed during puberty is androgen-dependent, but requires only a small amount of androgens secreted by the suprarenal gland.

Facial hair is the best example of androgen-dependent hair. There is a syndrome in which beard does not grow due to a lack of 5-alpha-reductase, and therefore it appears that testosterone must be reduced to DHT in order for facial hair to grow. Beard hair starts to grow on both sides of the upper lip towards the centre, followed by the cheeks and middle line of the chin. The rate growth of facial hair increases with time and after 35 it is believed to remain constant. Hair has been proven to grow faster in summer than in winter.
Body hair is also androgen-dependent. There are pharmacological substances that can block the DHT receptor, decreasing hair growth and reducing its diameter and pigmentation.

During puberty armpit and pubic area hair appears in both sexes, requiring small quantities of suprarenal androgens (puberty).

In males hair grows on the face, superior pubic triangle, chest, ears… In order for that hair to grow a bigger amount of androgens than that needed for armpit and pubic area hair is needed. These hormones are usually secreted by the testicles (late puberty and adulthood). These hormones stimulate hair growth in certain parts of the body and are responsible for hair regression and smaller size in the frontotemporal region of the scalp. Therefore, one hormone can produce different effects.

In women, when hair appears in typically male areas it must be determined whether the cause is organic or not. Other possible manifestations of androgenetic hyperactivity include:

Seborrhoea or oily skin
Acne
Oligoamenorrhoea or scarce or inexistent periods
Infertility due to lack of ovulation
Signs of virilization
Clitoromegalia (enlarged clitoris)
Male-pattern hair loss (receding hair line and no diffuse loss of hair)
Mammary atrophy
Deep voice