I feel that as a Medical Professional, I owe it to people to crack open an Embryology book and a Human Genetics book and enjoy this insomnia after a 12hr shift too explain why, in Science, the exception proves the rule, and the very existence of chromosomal abnormalities within the binary confirms we’re a binary, sexually dismorphic species.

One simple answer to the catch-all argument of “how do you know you aren’t intersex? Have you seen your karyotype?” is quite simple. Because your sexual development is normal and you are healthy - these are serious syndromes that affect the body and mind and sometimes reduce life expectancy. Simply, you’d know.

Now, I wanted a comprehensive list but I can’t spend the morning on OMIM and NCBI, so here’s a few of the most known syndromes of human sexual development in utero:

There are four characteristic intersex conditions recognized - 46 XX(congenital adrenal hyperplasia, mostly caused by aromatase deficiency), 46 XY (Like AIS, 5-alpha-reductase deficiency), true gonadal intersex and complex (Like Klinefelters, 45XO, 47XXX, etc)

Now let’s examine the symptom list of some of these syndromes:

CAH: Excessive or deficient production of sex steroids by the adrenal glands.

symptoms:

Due to inadequate mineralocorticoids:

vomiting due to salt-wasting leading to dehydration and death



Due to excess androgens:

functional and average sized penis in cases involving extreme virilization (but no sperm)

ambiguous genitalia, in some infants, such that it can be initially difficult to identify external genitalia as “male” or “female”.

early pubic hair and rapid growth in childhood

precocious puberty or failure of puberty to occur (sexual infantilism: absent or delayed puberty)

excessive facial hair, virilization, and/or menstrual irregularity in adolescence

infertility due to anovulation

clitoromegaly, enlarged clitoris and shallow vagina



Due to insufficient androgens and estrogens:

Undervirilization in XY males, which can result in apparently female external genitalia

In females, hypogonadism can cause sexual infantilism or abnormal pubertal development, infertility, and other reproductive system abnormalities

5-alpha-reductase-deficiency(PSEUDOVAGINAL PERINEOSCROTAL HYPOSPADIAS; PPSH): 5α-Reductase is an enzyme that converts testosterone to 5α-dihydrotestosterone (DHT) in peripheral tissues. 5-ARD is biochemically characterized by low to low-normal levels of testosterone and decreased levels of DHT, creating a higher testosterone/DHT ratio.

Signs:

Dihydrotestosterone (DHT) formation is defective in this condition. Testosterone and estrogen levels are normal, hence the lack of gynecomastia. Other evidence as well suggests that DHT is important to external virilization.

The affected males were born with ambiguous genitalia and masculinized at puberty without breast development. The testes were normal histologically. The patients had no mullerian structures, complete wolffian differentiation, small phallus, bifid scrotum, urogenital sinus with perineal hypospadias and blind vaginal pouch. At puberty, they showed male habitus with excellent muscular development, voice change, enlargement of phallus and production of semen, but small prostate and scanty beard. Plasma testosterone was normal; plasma 5-alpha-dihydrotestosterone was low. An abnormally small amount of radioactive testosterone was converted to dihydrotestosterone.

5-ARD is associated with an increased risk of cryptorchidism and testicular cancer.

Klinefelters (47XXY): set of symptoms that result from two or more X chromosomes in males

Signs: weaker muscles, greater height, poor coordination, less body hair, smaller genitals, breast growth, and less interest in sex. Often it is only at puberty that these symptoms are noticed. Intelligence is usually normal; however, reading difficulties and problems with speech are more common. Higher rates of breast cancer.

45XO: a condition in which a female is partly or completely missing an X chromosome

Signs:

Signs and symptoms vary among those affected. Often, a short and webbed neck, low-set ears, low hairline at the back of the neck, short stature, and swollen hands and feet are seen at birth. Typically, they only develop menstrual periods and breasts with hormone treatment, and are unable to have children without reproductive technology. Heart defects, diabetes, and low thyroid hormone occur more frequently. Most people with TS have normal intelligence. Many, however, have troubles with spatial visualization that may be needed for mathematics. Vision and hearing problems occur more often.

See the obvious pattern here? You’d know.

The other obvious pattern; those are serious conditions with serious comorbidies. Not “you can’t read my karyotype!”

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But MOST IMPORTANTLY, even with ambiguous genitalia, internal gonads, sex hormones gone haywire and chromosome abnormalities, these people are still classed as male or female. With the one true exception of true intersex, where the person might be XY, XX or both. The most common cause is exposure to pesticides.

Still, all combinations possible are X and Y, there’s no abnormal chromosome created OUTSIDE of the binary. There are no hormones yet unidentified. Biology has decoded embryology long ago and the absurdity of Sex denialism needs to end.

