Hormones are powerful chemical messengers produced by various glands in the body. They’re released directly into the bloodstream, where even tiny amounts can trigger significant biological changes.
Testicles produce testosterone, the primary male sex hormone and the precursor to the hormone responsible for hair loss. After puberty, the testicles begin producing enough testosterone to potentially trigger hair loss. It is not testosterone itself but its derivative, dihydrotestosterone (DHT), that causes androgenetic alopecia. DHT is formed when testosterone interacts with the enzyme 5-alpha reductase, which is found in areas such as the prostate, testes, adrenal glands, and—you guessed it—hair follicles.
DHT binds to genetically sensitive hair follicles, triggering longer rest periods between hair growth cycles and causing the hair shafts to miniaturize, eventually leading to baldness.
Finasteride (Propecia®) is an FDA-approved medication that can halt and even reverse follicle miniaturization in cases of male pattern baldness. works by blocking 5-alpha reductase, thereby reducing DHT production. This decrease in DHT can slow, stop, or even reverse the miniaturization process in some men.
Genes and hormones alone don’t cause hair loss—time also plays a role. The exact age when hair loss begins varies from person to person.
Hair follicles need to be exposed to DHT consistently over time for balding to occur. Factors like testosterone levels, the presence of 5-alpha reductase in follicles, and follicle sensitivity to DHT are all genetically determined.
Hair loss typically progresses in cycles, with alternating periods of rapid loss, slow loss, and stability. The reasons for these fluctuations aren’t fully understood, but we do know that hair volume tends to decline with age, regardless of genetic predisposition.
Even the “permanent zone” (the region of the scalp typically used for donor hair) experiences thinning over time. However, there is usually still enough hair for transplantation to remain a viable option, even for men in their 70s or older.
