Dihydrotestosterone (DHT) (referred to as androstanolone or stanolone when used medically) can also be used in place of testosterone as an androgen. The availability of DHT is limited; it is not available in the United States or Canada, for instance, but it is available in certain European countries, including the United Kingdom , France , Spain , Belgium , Italy , and Luxembourg .  DHT is available in formulations including topical gel, buccal or sublingual tablets, and as esters in oil for intramuscular injection.  Relative to testosterone, and similarly to many synthetic AAS, DHT has the potential advantages of not being locally potentiated in so-called androgenic tissues that express 5α-reductase (as DHT is already 5α-reduced) and of not being aromatized into an estrogen (it is not a substrate for aromatase).
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. 
Primobolan cycle can be a reason for the next side effects: