Finasteride is a widely used medication for male pattern baldness (androgenetic alopecia). While effective in promoting hair growth and preventing further hair loss, many individuals experience an initial period of increased hair shedding when they first begin treatment. This temporary phenomenon is a common part of the process as the medication starts to work.
The Hair Growth Cycle
Hair growth follows a natural, cyclical pattern involving distinct phases. The Anagen phase is the growth phase, where hair actively grows for approximately two to eight years for scalp hairs. The Catagen phase is a brief transitional period (one to two weeks), during which hair growth slows and the hair follicle prepares for rest. The Telogen phase is a resting stage (two to three months) where the hair follicle is inactive, before the Exogen phase when old hair sheds, making way for new hair growth. Losing around 50 to 100 hairs daily is a normal part of this continuous cycle.
Finasteride’s Action on Hair Follicles
Finasteride works by targeting a specific enzyme. It inhibits 5-alpha reductase, an enzyme responsible for converting testosterone into dihydrotestosterone (DHT). DHT is a potent androgen that plays a central role in male pattern baldness. In individuals genetically predisposed to hair loss, DHT binds to receptors on hair follicles, causing them to shrink over time in a process called miniaturization. This miniaturization leads to progressively finer, shorter, and weaker hairs, eventually resulting in hair loss. By reducing DHT levels in the scalp, finasteride helps to counteract this shrinking effect on the hair follicles.
The Mechanism Behind Shedding
The shedding experienced with finasteride is directly linked to its mechanism of action and the hair growth cycle. When finasteride reduces DHT levels, it prompts hair follicles that were previously miniaturized or in a weakened state to reset their growth cycle. These affected follicles, often in the resting (telogen) phase, are encouraged to prematurely enter a new growth (anagen) phase. For new, healthier hair to emerge, the old, weaker hairs occupying those follicles must be expelled. This synchronized expulsion of existing hairs makes way for the rejuvenated follicles to produce stronger, thicker strands. This temporary increase in hair loss is often a positive indication that the medication is effectively shifting the hair follicles towards a healthier growth pattern.
What to Expect During the Shedding Period
Increased hair shedding typically begins one to three months after starting finasteride treatment. This period of shedding is generally temporary, lasting from a few weeks to approximately two to three months. This shedding is part of the hair follicle’s reset process, indicating that the medication is beginning to work. While it can be unsettling to observe more hair loss, patience and consistent adherence to the treatment plan are beneficial. Many users start to see improvements in hair density and reduced shedding after about six months of continuous use, as the new, healthier hair growth becomes more evident.