That is dumb. Your optho is dealing outside his specialty and told you so when he said he is not sure. Many people talk people out of propecia just because they themselves can't benifit because they lost their hair already or got side effects. Also, he may have just wanted to mess with you. Or he heard this dumb myth somewhere else and just passed it on like most people do when they hear myths. Some doctors advocate adkins or something their preacher told them anything else, when others adhear to FDA rules. Some prescribe avodart, others don't. Just shows you that doctors aren't always right. I'm a college student and have worked with people headed for med school, and I can tell you that most just memorize the minimum for the test and fake the rest and are just flawed people who did not like their calculus class.
Propecia does two things:
1. give your liver a little more work
2. lower DHT levels
DHT looks like testosterone, and is one of the many derivatives your body makes naturally. All androgens cause hair loss, but DHT is by far the strongest, so keeping it in the form of testosterone is just better. The less DHT you have, the more testosterone you have. But because you have much mroe testosterone than DHT, testosterone levels don't change much.
All your side effects should revolve around tissue growth, masculinity, and sexual factors, and maybe some skin factors and gland factors. So pupil dialation would not be on the list. Nor are side pains or itchy butts or gas, though people have claimed them all as side effects on this forum daily.
