Defective CYP19A1 causes AEXS

Aromatase (CYP19A1) catalyses the conversion of androstenedione (ANDST) to estrone (E1). Defects in CYP19A1 can cause aromatase excess syndrome (AEXS; MIM:139300) and aromatase deficiency (AROD; MIM:613546). Affected individuals cannot synthesise endogenous estrogens. In females the lack of estrogen leads to pseudohermaphroditism and progressive virilization at puberty, whereas in males pubertal development is normal.

Summary from Reactome (R-HSA-5579030), read 2026-09-23.