Topical minoxidil does not act as an antiandrogen in the flank organ of the golden Syrian hamster.

Little is known about the mechanism of action of minoxidil-induced hair growth in male pattern baldness. We studied the potential antiandrogenic effect of topical minoxidil administered at the same dose and in the same vehicle that has been used successfully clinically in human subjects on the androgen-dependent cutaneous structures of the flank organ of the golden Syrian hamster. Minoxidil applied topically to one flank organ had no androgenic effect. Neither 1% nor 5% minoxidil topically applied for three weeks prevented the androgen-dependent growth of the pigmented spot, the sebaceous gland, or the hair follicle diameter induced by subcutaneous Silastic capsules filled with crystalline testosterone. As a positive control in the same experiments, 5% progesterone did significantly inhibit pigment and sebaceous gland enlargement. We conclude that there is no antiandrogenic component to the mechanism of action of topical minoxidil in the hamster flank organ, and thus there is probably no antiandrogenic role in man either.