Hormonal imbalances DO occur but their "effects" vary and as to those imbalances producing "stupendous sizes", well--seems highly questionable, IMHO.
One of the more common imbalances is too low a level which delays development and restricts growth to "full adult size". Caught early, a young man can be given treatment at the appropriate age and he can go on to more normal growth. Safe and successful hormonal treatment is not without considerable effort by an MD to determine the "correct balance". Too much adjustment (of testosterone) isn't going to produce a gigantic penis but instead throw the entire body out of whack in metabolism, heartrate, and other scary outcomes. Tampering with one's testosterone level is serious business. (One wouldn't think so, but it is!
For those (fewer) men who may happen to have an imbalance in the other direction(too much testosterone) they tend to have among other symptoms, excessive body hair, acne, and yes larger than average genitalia but NOT to proportions of 16 inch penises! The size of their penises might not be all that incredible (overall), but would be in comparison to their peers at their given age. They are "stand-outs" and draw attention.Guys with too much "t" often are often ahead of their peers in overall body growth and development (which sets up then social interaction concerns). There's also the risk of yet other (interrelated) health disturbances, too. So, it's not really funny (or even "fortunate") to have an excessive level of male hormones.
Dominik, I don't necessarily doubt your e-mail buddy could have a hormone problem. But his reported dimensions? --Hunh hunh.
(I think he's pulling your leg.)