Finasteride
Finasteride is a 5-alpha-reductase inhibitor, blocking the enzyme that converts testosterone into dihydrotestosterone. Lower DHT levels shrink prostate tissue over months and slow androgen-driven thinning of scalp hair. It is used for benign prostatic enlargement and for male pattern hair loss.
It can be taken with or without food, and its effect builds gradually rather than immediately, so benefit is judged over months. It roughly halves the PSA blood result, so any lab or urologist interpreting a prostate check needs to know the drug is being taken, otherwise a rising value can be masked. Testosterone and SHBG may shift while DHT falls, which is why they appear as markers worth following. Tablets should not be handled by a pregnant woman, since exposure can affect the development of a male fetus.
Reduced libido, erectile difficulty, mood changes, breast tenderness or a lump, or any new prostate symptom deserve a doctor's review rather than a private decision to stop. A PSA result read without accounting for this drug should also be rechecked with a doctor.
Reference information, not medical advice. Discuss any change with your doctor.