Aromatase Excess Syndrome, AES, or AEXS is an intersex trait where ones body produces an excess of estrogen, causing hyperfeminine traits in the body. This can effect CTF and CTM individuals alike, however when it effects CTF individuals, it is known as Hyperestrogenism. How common aromatase excess syndrome is unknown, however more than 20 cases have been described in the medical literature.

For AMAB/CTM individuals, symptoms include an early puberty, breast growth, wide hips, a higher pitched voice than usual, low hair growth, low sperm count, smaller than usual/missing testicles, a micropenis, and a shorter than average height. They are only occasionally able to reproduce. They may also have AMAB Hypogonadism.

In AFAB/CTF individuals, symptoms include menstrual irregularities, amenorrhea, abnormal vaginal bleeding, and enlargement of the uterus and breasts. If left untreated, hyperestrogenism may increase the risk of estrogen-sensitive cancers such as breast cancer later in life.

Those with this variation also tend to have early growth spurts and mood swings.

It is important to note that not all the symptoms listed in this page are guaranteed to occur in someone with this variation, as someone may only experience one or several of these symptoms, yet still hold the variation.


Rearrangements of genetic material involving what is known as the CYP19A1 gene can cause aromatase excess syndrome, especially in AMAB individuals. The CYP19A1 gene provides instructions for what is known as the enzyme aromatase that converts androgens to create different forms of estrogen, and if it overworks itself, it may provide more estrogen than needed.

In AFAB AES, hyperestrogenism can be caused by ovarian tumors, genetic variations, such as aromatase excess syndrome/familial hyperestrogenism, or overconsumption of exogenous sources of estrogen which may include medications used in hormone replacement therapy and hormonal contraception. Liver cirrhosis is another cause, though through lowered metabolism of estrogen, not oversecretion or overconsumption like the aforementioned. It's necessary to know there exist two kinds of hyperestrogenism: absolute (more concentration than usual of estrogen) and relative (can have a normal concentration of estrogen, but it's higher with respect to progesterone).

This variation can also be caused by many other variations of intersex as well.

CTM AES-causing variations: