5-alpha reductase deficiency is one of several conditions where girls are born with XY karyotype (the usual male pattern). It is characterized by an absence of the enzyme 5-alpha reductase, which converts testosterone change to dihydrotestosterone (DHT). Without DHT, prenatal genital development results in female appearance. Because masculine puberty depends more strongly on testosterone than on DHT, puberty will be virilizing (unless the gonads are removed or a blocking medication is used).

The adrenal glands, located above the kidneys, are the pair of glands that are responsible for secreting various hormones, including androgens.

This means working with a child in a way that works with her or his level of understanding. For example, if you’re talking with a child about going to the doctor, it would be “age-appropriate” with most three-year-olds to use a stuffed animal to explain what’s going to happen at the doctor’s office, but not age-appropriate to do the same with an intelligent teenager. Parents should not “dumb down” things unnecessarily, but they should also be careful not to talk over the head of their children.

Androgen Insensitivity Syndrome (AIS) occurs when an individual has one X and one Y chromosome, but the body is unable to respond to androgens (male sex hormones). A person with complete AIS will develop female genitalia, while a person with partial AIS may have genitalia that appear mainly female, or mainly male, or anything in between.

Androgens are hormones (molecules or chemical messengers) made mostly by the testes, but also made to a lesser extent in the adrenal glands located above the kidneys, and in the ovaries. They stimulate male reproductive organ (sex organ) development and secondary sex characteristics such as facial hair and lower pitch of voice. The two major types of androgens involved in sex development are testosterone and dihydrotestosterone.

See Mullerian inhibiting substance.

Aphallia refers to being born without a penis, in a patient with otherwise typical male anatomy.

A scrotum that is separated by a deep cleft or groove into two parts.

A curving of the penis that can cause very painful erections. Pronounced like "cord ee" (the h is silent).

These are the long strands of tightly curled DNA that reside within the nucleus of all cells (except red blood cells). Each cell in your body has a full set of your chromosomes. The chromosomes contain the body’s genes, which are specific segments of DNA that contain the messages for the cell to create proteins, some of the building blocks of life. So the chromosomes have the genes, and the genes code for the proteins, and the proteins form things like blood, skin, and other organs. Most people have 46 chromosomes in each cell: that includes 22 pairs (which scientists number 1 to 22, from largest to smallest) of closely matching chromosomes (one of each pair from each parent) called autosomes. In addition to those 22 pairs, most people have two additional chromosomes that may or may not match, and these are called the “sex chromosomes.” Instead of being numbered like the autosomes are, the sex chromosomes are designated by the letters X and Y, because they kind of look like an X and a Y. Most females have two so-called X chromosomes, and so we say they have the karyotype 46,XX; the number 46 tells you they have 46 chromosomes total, and the “XX” tells you that two of those chromosomes are X chromosomes. Most males have one X chromosome and one Y chromosome, and so we say they have the karyotype 46,XY (46 chromosomes, including one X and one Y). However, there are many other patterns of chromosomes. Some people have an extra X or Y, some are missing an X, some females have a Y chromosome and some males have two X’s. The “sex chromosomes” are somewhat misnamed, because, although they are usually different between males and females, they are not by themselves responsible for whether a person develops as a male or female. There are many genes carried on many other chromosomes (autosomes) that are also responsible for development of the gonads and other sex aspects. There are also some genes on the X chromosome that don’t have anything to do with sex development. It’s critical to understand that “sex chromosomes” do not determine a person’s gender identity or sexual orientation.

Clitoromegaly means that the clitoris is larger than expected.

Congenital adrenal hyperplasia (CAH) refers to any of several genetic conditions affecting the production of cortisol by the adrenal glands. Most of these conditions also result in altered production of sex steroids (hormones) by the adrenals, and can alter development of sexual characteristics.

A cosmetic surgery is one that only affects appearance, rather than making a body part work better or curing an illness.

This usually means the name of a cause of a DSD (for instance, “congenital adrenal hyperplasia” or "complete androgen insensitivity syndrome”). Doctors decide on a diagnosis by considering the signs and symptoms, the family history, and the results of various tests. In many cases, it is not possible to arrive at a definite cause. In that case, doctors may use a descriptive word, like “ambiguous genitalia” for the diagnosis.

Dihydrotestosterone (DHT) is an androgen (male sex hormone) produced by converting testosterone into dihydrotestosterone. DHT is an important factor in the development of male genitalia before birth.