The enzyme aromatase converts androgens to estrogens. In the rare, autosomal recessive condition of aromatase deficiency, gene mutations result in decreased aromatase activity, leading to androgen excess and estrogen deficiency in males and females.

Aromatase deficiency is a cause of female pseudohermaphroditism (or disorder of sex development). Aromatase is an enzyme that converts androgen hormones to estradiol, an estrogen. Deficiency in this enzyme leads to excessive exposure of a fetus to androgens, resulting in virilization of the external genitalia. Virilization of the mother during pregnancy can also occur.

Other signs of aromatase deficiency are failure of puberty to progress, hypergonadotropic hypogonadism, polycystic ovaries, tall stature, and osteopenia.

Males with aromatase deficiency have normal external genitalia and puberty, but are still affected by osteoporosis and tall stature. Aromatase deficiency is caused by a mutation in the CYP19 gene.