Finasteride works by inhibiting the enzyme 5α-reductase. This enzyme converts testosterone to dihydrotestosterone (DHT), a potent androgen implicated in hair loss and benign prostatic hyperplasia (BPH). By blocking 5α-reductase, finasteride significantly reduces DHT levels. Lower DHT levels lead to reduced hair follicle miniaturization in men with male pattern baldness, slowing hair loss or even promoting regrowth. In BPH, reduced DHT leads to shrinkage of the prostate gland, improving urinary symptoms.
Types of 5α-Reductase and Finasteride’s Specificity
Two main types of 5α-reductase exist: type 1 and type 2. Finasteride primarily inhibits type 2, which is predominantly found in the prostate and scalp. This explains its effectiveness in treating BPH and male pattern baldness. The impact on type 1 is less significant.
Pharmacokinetics and Potential Side Effects
Finasteride is absorbed orally and metabolized primarily in the liver. It achieves therapeutic levels within a few weeks. While generally well-tolerated, potential side effects include decreased libido, erectile dysfunction, and gynecomastia. These side effects typically diminish upon cessation of treatment. Always consult your doctor before starting or stopping finasteride.
