Finasteride is a medication primarily used for male pattern hair loss and benign prostatic hyperplasia (enlarged prostate). It works by targeting dihydrotestosterone (DHT), a potent androgen. Understanding DHT’s role is key to how Finasteride operates.
Understanding DHT and Finasteride
Dihydrotestosterone, or DHT, is a hormone derived from testosterone, the primary male sex hormone. It is created through the action of an enzyme called 5-alpha-reductase, which converts a portion of the body’s testosterone into this more potent form. DHT plays various roles throughout the body, including contributing to the development of male sexual characteristics during puberty, such as facial and body hair growth, and the maturation of the prostate gland.
In adulthood, elevated levels of DHT can contribute to certain conditions. For instance, it is implicated in male pattern baldness, where it can cause hair follicles to shrink, and in the enlargement of the prostate gland, known as benign prostatic hyperplasia. Finasteride is a medication designed to inhibit the enzyme responsible for this conversion, thereby reducing the amount of DHT in the body.
The Mechanism of DHT Blockage
Finasteride functions as a specific inhibitor of the 5-alpha-reductase enzyme. This enzyme exists in different forms, or isoenzymes, within the body. Finasteride primarily targets and inhibits the Type 2 isoenzyme of 5-alpha-reductase, which is predominantly found in tissues like hair follicles and the prostate.
By blocking this enzyme’s activity, Finasteride effectively reduces the conversion of testosterone into DHT. This action decreases DHT concentrations in tissues where the Type 2 enzyme is active.
Quantifying DHT Reduction
Finasteride significantly reduces DHT levels in both the bloodstream and specific tissues. For the treatment of male pattern hair loss, the typical dosage is 1 milligram (mg) daily. This dose has been shown to reduce serum (blood) DHT levels by approximately 70% to 71%. Concurrently, it can decrease DHT levels in the scalp, where hair follicles are located, by about 60% to 64%.
For benign prostatic hyperplasia, a higher 5 mg dose is often prescribed. This dose also reduces serum DHT by 70% to 72%. In the prostate gland, the 5 mg dose lowers DHT levels by over 90%. The 1 mg dose is largely effective for systemic DHT inhibition relevant to hair loss.
Biological Effects of Reduced DHT
The reduction in DHT levels due to Finasteride leads to several biological outcomes. For hair loss, lower DHT concentrations help reduce hair follicle miniaturization, where follicles shrink and produce finer hairs. This action can slow further hair loss and promote the regrowth of thicker hair.
For an enlarged prostate, decreased DHT contributes to a reduction in prostate size. This can alleviate urinary symptoms associated with benign prostatic hyperplasia. Finasteride can also lead to a slight increase in testosterone levels. Some individuals may experience changes in sexual function, such as decreased libido or erectile dysfunction, or breast tissue enlargement.