Aromatase excess syndrome

Aromatase excess syndrome (AES or AEXS), also sometimes referred to as familial hyperestrogenism or familial gynecomastia, is a rare genetic and endocrine syndrome which is characterized by an overexpression of aromatase, the enzyme responsible for the biosynthesis of the estrogen sex hormones from the androgens, in turn resulting in excessive levels of circulating estrogens and, accordingly, symptoms of hyperestrogenism. It affects both sexes, manifesting itself in males as marked or complete phenotypical feminization (with the exception of the genitalia; i.e., no pseudohermaphroditism) and in females as hyperfeminization.