Miniaturization and Progression of Thinning Hair

It is important to understand the normal hair growth cycle to understand why thinning hair occurs. The hair follicle is an anatomical structure which evolves to produce and push out a hair shaft. Human hair grows in a continuous cyclic pattern known as the hair growth cycle.

The normal hair growth cycle starts with Anagen, which is the growth phase; Catagen or the degradation phase; and Telogen, also known as the resting phase. Periods of growth (anagen) between two and eight years are followed by a brief period, two to four weeks, in which the follicle is almost totally degraded (catagen). The resting phase (telogen) then begins and lasts two to four months. Shedding of hair occurs only after the next growth cycle (anagen) begins and a new hair shaft begins to emerge. On average, 50-100 telogen hairs are shed every day. This is normal hair loss and accounts for the hair loss seen every day in the shower and with hair combing. These hairs will regrow. Not more than 10 percent of the follicles are in the resting phase (telogen) at any time. A variety of factors can affect the hair growth cycle and cause temporary or permanent hair loss like medication, radiation, chemotherapy, exposure to chemicals, hormonal and nutritional factors, thyroid disease, generalized or local skin disease, and stress.

“Miniaturization” is a word used to describe the progression of thinning hair. It is synonymous with the genetic condition androgenic alopecia or pattern hair thinning. Miniaturization is a process where hair follicles that are producing healthy hairs begin to produce thinner, shorter, more brittle hairs with weaker shafts. These hairs are less dense and lead to the appearance of thinning hair. According to the Foundation of Hair Restoration, androgenic alopecia or genetic miniaturization is responsible for 95 percent of all hair loss cases.

The onset of miniaturization from androgenic alopecia is due to three factors. Genetic predisposition is the first factor. Miniaturization of hair is genetic and can come from either side of your family or both. The presence of dihydrotestosterone, or DHT, is the second factor. DHT is the primary hormone linked to hair loss. Age is the third factor. The older you are, the more likely you are to experience miniaturization of your hair.

DHT is the primary hormone associated with miniaturization of hair follicles. Testosterone naturally converts to DHT through a hormonal pathway called the 5 alpha reductase. Certain hairs on your head may be genetically susceptible to thin if exposed to excess levels of DHT. DHT can attach to hair follicle, prematurely make it shed and begin to shrink the follicle. Instead of a normal, healthy hair regrowing in its place, thinning hair replaces it.