As we discussed above, Dianabol carries a strong aromatizing nature, and is a C17-aa anabolic steroid; as such, its side-effects will revolve around these factors. As an aromatizing steroid, this means there can be a testosterone to estrogen conversion, and if estrogen levels go to high it can lead to some complications. When estrogen levels increase, the hormone can attach to the receptors and cause gynecomastia (male-breast enlargement) and it can also promote excess water retention and high blood pressure; Dbol is notorious for promoting high blood pressure. Needless to say, if you already suffer from high blood pressure you should not touch this steroid, but if it's healthy you'll need to ensure it stays this way. For this reason, in-order to combat and avoid these estrogenic side-effects of Dbol, the use of an Aromatase Inhibitor (AI) is often advised. It shouldn't be too hard to see how this can help; after all, an AI inhibits aromatase, but it goes a step further by reducing the body's total estrogen levels. Of course, and this cannot be overstressed, you must keep your doses at a responsible level; most will need at least 20mg per day for any anabolic promotion, with a maximum dosing of 50mg per day. It should be noted; if you've never used this steroid before, you should not start with a high end dose; start low and see how you respond.
A number of investigators have reported on a rather rare syndrome of excess aromatase activity. In boys, it can lead to gynecomastia , and in girls to precocious puberty and gigantomastia . In both sexes, early epiphyseal closure leads to short stature. This condition is due to mutations in the CYP19A1 gene which encodes aromatase.  It is inherited in an autosomal dominant fashion.  It has been suggested that the pharaoh Akhenaten and other members of his family may have suffered from this disorder,  but more recent genetic tests suggest otherwise.  It is one of the causes of familial precocious puberty—a condition first described in 1937.