Dihydrotestosterone or DHT, an androgen, is the most potent male hormone. It is produced when testosterone and an enzyme called 5α-reductase are synthesized in the prostate, adrenal glands, testes and hair follicles.
DHT is responsible for the development of sexual characteristics during puberty. As men age, dihydrotestosterone has a tendency to be produced more rapidly. The older a man gets, the less DHT is used so it begins to build up in the body.
Among other things, the buildup of DHT causes prostate cancer. It also clogs hair follicles and blocks necessary nutrients which compromises healthy hair growth.
Hair follicles in the back of the head are resistant to DHT which is why elderly men with major hair loss still have a horseshoe of hair in the back of their head. This area is where donor tissue is harvested for a hair transplant. This donor tissue contains hair follicles that have been pre-programmed to stay healthy and are resistant to DHT. After transplantation, they remain permanent unless they were genetically preprogrammed to fall out.
As early as 1992, the US Food and Drug administration approved a drug called Finasteride, eventually marketed as Proscar and Propecia. It is used to treat prostate cancer and male pattern baldness. Finasteride prevents the conversion of testosterone to DHT and the unhealthy buildup in hair follicles which causes hair loss. Finasteride can be used effectively as a hair loss treatment. Hair transplant patients can effectively fight future hair loss with this drug.
Finasteride is known to cause birth defects and should not be taken or even handled by pregnant women or women who may become pregnant.