Estrogen insensitivity syndrome

Estrogen insensitivity syndrome, abbreviated EIS and also called estrogen resistance, is a form of congenital estrogen deficiency, or hypoestrogenism, caused by a defective estrogen receptor, specifically estrogen receptor alpha. Because of the defect the body cannot respond to estrogen even though the hormone is present. Congenital estrogen deficiency can also arise from a defect in aromatase, the enzyme that makes estrogens, which is called aromatase deficiency and resembles EIS in its symptoms. The condition is extremely rare: as of 2016 only three published reports existed, covering five individuals, a male case in 1994, a female case in 2013 and a family of two sisters and a brother in 2016. It is the counterpart of androgen insensitivity syndrome, and its functional opposite is hyperestrogenism. This entry records the source and is not medical advice.