[2] Additionally, in another study, androstenedione, testosterone, and dihydrotestosterone (DHT) were found to be either low or normal in males, and follicle-stimulating hormone (FSH) levels were very low (likely due to suppression by estrogen, which has antigonadotropic effects as a form of negative feedback inhibition on sex steroid production in sufficiently high amounts),[6] whereas luteinizing hormone (LH) levels were normal.

[1] This has been suggested to be due to in situ conversion of adrenal androgens into estrone and then estradiol (via local 17β-HSD) in breast tissue (where aromatase activity may be particularly high).

[1] The symptoms of AEXS, in males, include heterosexual precocity (precocious puberty with phenotypically-inappropriate secondary sexual characteristics; i.e., a fully or mostly feminized appearance), severe prepubertal or peripubertal gynecomastia (development of breasts in males before or around puberty), high-pitched voice, sparse facial hair, hypogonadism (dysfunctional gonads), oligozoospermia (low sperm count), small testes, micropenis (an unusually small penis), advanced bone maturation, an earlier peak height velocity (an accelerated rate of growth in regards to height),[8] and short final stature due to early epiphyseal closure.

[1] In females, symptoms of AEXS include isosexual precocity (precocious puberty with phenotypically-appropriate secondary sexual characteristics), macromastia (excessively large breasts), an enlarged uterus, menstrual irregularities, and, similarly to males, accelerated bone maturation and short final height.

[9][10] Fertility, though usually affected to one degree or another—especially in males—is not always impaired significantly enough to prevent sexual reproduction, as evidenced by vertical transmission of the condition by both sexes.

[2][3][4] The root cause of AEXS is not entirely clear, but it has been elucidated that inheritable, autosomal dominant genetic mutations affecting CYP19A1, the gene which encodes aromatase, are involved in its etiology.