What It Is
The hormone 17-hydroxyprogesterone is a building block for producing the hormone cortisol. Cortisol is produced mainly by the adrenal cortex (the outer part of the two adrenal glands, located above the kidneys). Cortisol is called the "stress hormone" because it's secreted in larger amounts as part of the body's response to physical or emotional stress.
Cortisol levels normally vary throughout the day. They're highest in the morning, just before waking up, and lowest at night.
Some people, however, can't make enough cortisol because they lack an enzyme in the adrenal glands that's needed to make it. They'll have a buildup of 17-hydroxyprogesterone in the blood because it's not being converted to cortisol.
In kids, the most common cause of cortisol deficiency, and consequently high levels of 17-hydroxyprogesterone, is one of the forms of the genetic disorder congenital adrenal hyperplasia (CAH).
CAH can affect both boys and girls. It causes the adrenal glands to make excess androgens (male steroid hormones) and, in some cases, not enough of the hormones that regulate the body's salt balance.
Though treatable, undetected CAH can sometimes lead to more serious symptoms such as dehydration and shock in infants.
Why It's Done
The 17-hydroxyprogesterone test is mainly used to check for the most common form of CAH in infants and children. In some states, it's done as part of a group of routine screening tests done on all newborns to allow early detection and treatment of certain diseases. In other states, it's performed only when symptoms warrant testing or when there's a family history of CAH.
Unless it's severe, CAH symptoms may be hard to spot in infant boys. In baby girls, the most common sign is ambiguous genitalia (a problem with genital development in which the genitals aren't clearly male or clearly female).
In milder forms of the condition, symptoms don't show up until after infancy. These can include early changes of puberty in both males and females, and masculine features in girls.
The test is also used to help doctors monitor the treatment of children with CAH. Kids with any of these symptoms would likely have a 17-hydroxyprogesterone test done, along with other hormone tests to check adrenal function.
Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.