Sexuality--When Things Go Differently

1. What do we mean by normal sexual development?
   Some 99 percent of humanity are born as males or females in their anatomy and physiological functioning. If the zygote is 46,XX this will lead to a baby girl at birth who will have a vagina and external pudenda and a uterus and oviducts and ovaries. She will have a menarche about age 13, probably have one or more children, and experience menopause about age 50. She will probably be married and at some point spend a lot of time raising children. Similarly if the zygote is 46,XY this will lead to a baby boy who will have a penis and scrotum testes, and a sperm transport system. He will begin ejaculating in his teens and in all likelihood father one or more children and spend a good part of his young adulthood raising a family. About 2 to 10 percent of adolescents will discover that although they are anatomically male they are attracted not to women but to other men. Similarly a small percentage (2 to 10 percent) of females who are anatomically and physiologically female will discover they are attracted to females. Until the 1970s homosexual orientation was considered a pathology. It no longer is, but the reason why this percent have such an orientation is still debated.

2. What do we mean by abnormal sexual development?
   Unless people believe illness is a social construction (a few do) people with abnormalities seek medical advice and treatment. No one believes wishing away a tumor, a heart attack, or a stroke is possible. The reproductive system is as vulnerable as any other organ system to disabilities. Some of these are caused chromosomal sex disturbances (e.g., Turner syndrome, Klinefelter syndrome, mosaicism, chimerism). Some are caused by genetic sex disturbances. In general genetic sex mutations lead to pathologies. These include sex reversals (XY females or XX males); male pseudohermaphrodites; and female pseudohermaphrodites.

3. What causes sex reversal?
   Some cases of sex reversal are caused by mutation or deletion of the SRY gene in the Y chromosome. Such XY zygotes lacking a functional SRY produce ovaries (sterile) and not testes. Thus there is no MIS and no testosterone. Thus the mullerian structures form a uterus, oviducts and upper vagina. The pudenda in the absence of testosterone are female (vagina, labia and clitoris). There may also be pubertal failure (no menarche, no breast development). Sometimes the SRY gene can be accidentally moved into an X chromosome. Then at fertilization the X with SRY encounters the egg's X and the XX zygote forms a male at birth with penis and scrotum and testes (sterile because the genes for spermatogenesis on the Y are missing). There will be MIS and testosterone so the sperm transport system is present and there are no major mullerian derivatives.

4. What is a female pseudohermaphrodite?
   A female pseudohermaphrodite has ovaries and some male internal or external genital sex development. The most common cause is a mutation (autosomal recessive) of the adrenal glands. When steroid hormones are made, the mutation prevent formation of a key hormone called cortisol. Without cortisol the pituitary cannot turn off the flow of a grwo0th hormone (ACTH or adrenocorticotrophic hormone) that stimulates enlargement of the adrenal glands. This leads to a flooding of other steroid products, including testosterone from the gland. If the embryo is forming its external genitalia and is awash with testosterone in such an XX embryo, the external genitalia will become male with a penis and scrotum (complete or bifid). In a few cases the child may be raised as a male and at puberty will begin menstruating through the penis. These adrenal conditions are usually called hyperadrenogenital syndrome.

5. What is a male pseudohermaphrodite?
   A male pseudohermaphrodite has testes and some female internal or external genital sex development. One category involves the failure to respond to MIS. In such an XY embryo the mullerian ducts form an internal uterus, oviducts, and upper vagina in an otherwise normal (and sometimes fertile) male. This condition is called congenital insensitivity to mullerian inhibiting substance. Another failure may be to receptors of testosterone. Such XY zygotes have testes that produce both MIS and testosterone but the target tissues for the testosterone are defective. Thus there is no Mullerian development but neither is there a sperm transport system nor formation of male external genitalia. Instead there is clitoris and labia at birth with a short lower vagina. Such a female male enter puberty with breast development but no pubic hair or menarche (and she has internal testes). This condition is called congenital insensitivity to androgen syndrome.

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