Male androgenetic alopecia is due to the effect of androgens on the hair follicles, while there is also a genetic predisposition for its appearance. Androgens are important growth hormones of the male sex. They control the function of the sebaceous glands, stimulate the growth of body and facial hair, and suppress the growth of hair in the frontotemporal region, leading to androgenetic alopecia.
In men who suffer from androgenetic alopecia, the enzyme 5-alpha-reductase is increased. They also display elevated levels of free testosterone and dihydrotestosterone and reduced levels of total androgens. In the hair follicle, 5-alpha-reductase converts free testosterone into dihydrotestosterone (DHT), which plays a dominant role. Both genetic and environmental factors play a role in its emergence and development, while the full causes still remain unknown. Other factors that contribute to the development of androgenetic alopecia are mental illness, heart disease and prostate cancer.
The responsible genes are being investigated; the majority of these are located on the X chromosome and are recessive. This is why women more rarely suffer from androgenetic alopecia, as it requires the existence of pathological genes on both X chromosomes to manifest itself. In men, a single gene on the only X chromosome available suffices to exhibit the disorder. Recent research has shown that the hereditary substrate of androgenetic alopecia is even more complex; genes have been found that control, among others, the time of onset of androgenetic alopecia, the speed of its development and the manner of manifestation.
Apart from heredity, other factors that lead to female androgenetic alopecia are the reduction of female hormones during menopause, the polycystic ovary syndrome, the congenital adrenal hyperplasia, the virilising adrenal and ovarian tumours, Cushing‛s syndrome, chronic use of cortisone. A recent study in identical female twins revealed several factors that can be associated with an increased incidence of androgenetic alopecia in women. Such factors are diabetes mellitus, hypertension, lack of exercise, long hours of sleep and an unstable marital relationship. Also, not wearing a hat and overexposure to UV radiation contribute to the onset androgenetic alopecia in women. Finally, anxiety and stress accelerate the condition in both men and women.