These changes typically begin gradually in men in their 20s.
Doctors believe male pattern hair loss is due to heredity and is dependent on hormonal effects.
Doctors studied over 1,800 men aged 18 to 41 with mild to moderate amounts of ongoing hair loss. In general, men who took Propecia maintained or increased the number of visible scalp hairs and noticed improvement in their hair in the first year, with the effect maintained in the second year. Hair counts in men who did not take Propecia continued to decrease. Propecia did not appear to affect hair loss in places other than the scalp. All trademarks and registered trademarks are of their respective companies.