You're actually talking about several things here:
They are each just a smidge different, but, each relates to your genes and steroid receptors, and your response to estrogen, and progesterone, as well as your body's modality for fat storage. (Estrogen is a steroid, of course, which is responsible for feminization. Prolactin is a protein peptide, and relates to progesterone, another steroid, which triggers lactation.)http://en.wikipedia.org/wiki/Gynecomastiahttp://en.wikipedia.org/wiki/Estrogen
Please note that while joescorpio1970 is in complete error regarding surgery as an only option, PSBigJoey is also in error regarding his remarks about gyno. Gyno, and lipomastia, are one and the same.http://en.wikipedia.org/wiki/Prolactinhttp://en.wikipedia.org/wiki/Progesterone
Only about 1/3 of all men have active receptors for these steroid(s) in the chest region. Other guys, such as myself, don't have the receptor, and remain unaffected.
Aromatase inhibs / competitive compounds are generally used for this. Surgery is NOT the only option, as I said above.http://en.wikipedia.org/wiki/Aromatase_inhibitor