
Originally Posted by
Elesirdur
Yeah, but it's a different kind of testosterone. True male pattern baldness or androgenic alopecia, not just alopecia areata, seems to be caused by elevated levels of Dihydrotestosterone (DHT) which also may (the scientific community is still working on this, according to Wikipedia) increase rates of prostate complications like prostate cancer, and acne.
DHT causes hair loss by kind of shrinking the hair follicles which makes hair thinner, more prone to fall out quicker, and eventually not be able to grow hair at all. Rogaine works to 'open up' the follicles and allow hair to grow in existing follicles, or strengthen already thin hair strands. However, rogaine doesn't work for everyone, especially those with elevated DHT induced androgenic alopecia, but works better for those who suffer from something more like alopecia areata - and only at the crown. If you're balding at the vertex and the crown, chances are rogaine won't do shit for you because rogaine doesn't get to the cause of the matter, elevated DHT, but is just a stop-gap solution.
Propecia, or Finasteride as the generic drug is known, actually acts to lower DHT levels in your body, which can prevent the follicle shrinking from taking place, or at least just slow it down. However, with the lowering of DHT levels, you may end up effects associated with higher estrogen levels like reduced sex drive, loss of androgenic hair (face, body), and even moobs. I think Finasteride was first designed to help people with prostate problems and, like Viagra, found it had another beneficial side-effect.
On the plus side, noticing your thinning hair might be a good reason to go get in shape and eat a more balanced diet. Even though the actual results haven't been linked in true scientific studies, it's thought that a good aerobic exercise routine and a low-calorie diet can help reduce the amount of insulin produced in your body, which through some mechanisms I can't remember, can reduce the levels of DHT in your body which affect hair follicle shrinkage. It's no magic bullet, that's for sure, but it may help a little and it's way better to be a guy with thinning hair or who is balding that's in good shape, than to be bald(ing) and out of shape.