DHT or Dihydrotestosterone (5a-Dihydrotestosterone) is a male sex hormone, a potent form of testosterone that is converted from testosterone by the enzyme 5a-reductase, an enzyme that synthesizes DHT in the adrenal glands, hair follicles, testes and prostate.
It is known that DHT plays a major role in hair loss but the process is not well understood. Many medications have been proven to interfere with DHT but have mixed results.
A critical part of the hair follicle is the dermal papilla which is responsible for the growth of the hair shaft. It is the "engine" of hair growth and is supplied with nutrients required for proper hair follicle growth by being in direct contact with the blood supply.
A reason DHT may play such a critical role in hair loss is that the dermal papilla(DP) have a large number of androgen receptors and males have many more compared to females. Further, DHT is 5 times more attracted to these DP androgen receptors than normal testosterone. Hair on the vertex and frontal regions of the scalp have been shown to contain many more receptors than on other parts of the scalp thus giving a balding man the typical horseshoe effect.