Finasteride is a synthetic 4-azasteroid compound and a specific inhibitor of type II 5-alpha reductase, an intracellular enzyme that converts testosterone to dihydrotestosterone (DHT), a more potent androgen responsible for the development and enlargement of the prostate gland and hair follicles. By inhibiting this enzyme, finasteride effectively reduces DHT levels in the scalp and prostate, leading to a decrease in prostate size and a slowing of hair loss in men with androgenetic alopecia (male pattern baldness). Finasteride is commonly prescribed for the treatment of benign prostatic hyperplasia (BPH), a condition characterized by an enlarged prostate gland, which can cause urinary difficulties. It is also used to treat male pattern hair loss in a lower dose. While finasteride can improve symptoms associated with BPH and slow hair loss, it may also lead to side effects, including decreased libido, erectile dysfunction, and a reduced volume of ejaculate. These side effects are generally reversible upon discontinuation of the medication. Patients considering finasteride for the treatment of BPH or hair loss should discuss the potential benefits and risks with their healthcare provider.