Diagnosing Congenital Adrenal Hyperplasia
Specialists at Hassenfeld Children’s Hospital at NYU Langone are experienced in diagnosing congenital adrenal hyperplasia, an inherited condition in which the adrenal glands produce abnormal levels of certain hormones, including cortisol and aldosterone. These hormones play an important role in many body functions, such as growth and blood pressure.
The adrenal glands use the enzyme 21-hydroxylase to convert the hormone 17-hydroxyprogesterone, or 17-OHP, into cortisol and aldosterone. Cortisol regulates blood sugar levels and the body’s response to stress and illness; aldosterone maintains salt and water levels, which help regulate blood pressure and prevent dehydration.
The adrenal glands also produce androgens, hormones that promote muscle growth and cause the development of underarm and pubic hair during puberty.
Children who inherit two mutations in the gene that makes 21-hydroxylase, called CYP21A2, don’t have enough cortisol and aldosterone. The 17-OHP that is not made into cortisol and aldosterone is then converted into androgens. Children whose parents carry an atypical CYP21A2 gene or have a family history of congenital adrenal hyperplasia are at increased risk of developing the condition.
Symptoms vary depending on the type of congenital adrenal hyperplasia your child has.
About 75 percent of children with the classic type have the salt-wasting form of the condition, which can lead to a life-threatening drop in blood pressure. It can cause vomiting, weight loss, and dehydration in the first few weeks of life. Without immediate treatment, a baby can go into shock, in which low blood pressure prevents oxygen and nutrients from reaching organs.
Other symptoms include ambiguous or masculine-looking genitals in baby girls and an enlarged penis in baby boys.
The type known as simple virilizing congenital adrenal hyperplasia affects a child’s sex characteristics. Girls are usually born with ambiguous genitals that have masculine characteristics. Other symptoms—such as excessive body hair, a deep voice, absent or irregular menstrual periods, severe acne, and thinning hair on the head—may appear as a girl enters puberty. A buildup of androgens can also increase the risk of polycystic ovary syndrome, or PCOS, during adolescence.
Boys with simple virilizing congenital adrenal hyperplasia may have an enlarged penis, early development of pubic and facial hair, early muscle growth, and severe acne. They are also at increased risk of developing testicular adrenal rest tumors during adolescence and adulthood. These tumors are composed of enlarged adrenal cells that are normally present in the testes. Left untreated, adrenal rest tumors can lead to infertility.
Many children with the classic form of congenital adrenal hyperplasia experience rapid bone growth early in childhood. Both girls and boys with classic congenital adrenal hyperplasia may experience early puberty, which can begin at around age eight for girls and nine for boys.
Symptoms of the mildest type, called nonclassic congenital adrenal hyperplasia, are not usually noticed unless girls and boys experience symptoms that mimic early puberty, such as early growth of facial and underarm hair. Excess androgen levels in both boys and girls can increase the risk of infertility during adulthood.
Our doctors diagnose the classic type of congenital adrenal hyperplasia with prenatal tests, as well as tests performed after a baby is born. The doctor may recommend additional tests to determine the type and severity of congenital adrenal hyperplasia your child has.
Prenatal tests, such as amniocentesis or chorionic villus sampling, can be used to diagnose congenital adrenal hyperplasia in an unborn child. Your obstetrician may recommend these tests if the child has an older sibling with the condition or if a family member has congenital adrenal hyperplasia or carries a gene mutation that decreases production of the enzyme 21-hydroxylase.
Both amniocentesis and chorionic villus sampling are used to determine whether an unborn child carries gene mutations associated with congenital adrenal hyperplasia. In amniocentesis, your doctor removes a sample of the amniotic fluid surrounding the unborn child. In chorionic villus sampling, your doctor removes a sample of tissue from the placenta, a temporary organ that delivers oxygen and nutrients to a baby in the womb.
If prenatal tests suggest that your baby has congenital adrenal hyperplasia, your child’s doctor examines the appearance of your newborn’s genitals and looks for signs of early sexual or physical development.
Your child’s doctor may order blood tests to measure the hormones cortisol, aldosterone, and androgens, as well as their chemical precursors—which help produce these substances—such as the hormone 17-OHP. These tests also measure levels of renin, an enzyme that signals the adrenal glands to produce more aldosterone. Additional blood tests measure levels of sodium, which may be lower in children with congenital adrenal hyperplasia, and potassium, which is often higher.
ACTH Stimulation Test
An ACTH stimulation test is used to diagnose congenital adrenal hyperplasia and determine the type your child has. Blood samples are taken before and after giving your child an injection of synthetic ACTH, or adrenocorticotropic hormone, which signals the adrenal glands to release the hormone cortisol. The first blood test establishes a baseline of the hormones in the blood.
After the injection, your child’s blood is tested to measure any change in levels of the hormones 17-OHP and androgens. Children who do not have congenital adrenal hyperplasia experience a very small increase in 17-OHP and androgens after the injection, whereas children with nonclassic congenital adrenal hyperplasia experience a significant increase in these substances. In children with classic congenital adrenal hyperplasia, the increase is even greater.
Doctors may recommend a blood test to look for the presence or absence of, or a mutation in, the gene that helps produce the enzyme 21-hydroxylase, which is needed to produce cortisol and aldosterone. This test may also be used to determine whether your child has classic or nonclassic congenital adrenal hyperplasia.
Identification of a specific gene mutation may prompt you to look for the mutation with prenatal tests during subsequent pregnancies.
Doctors may use a urine test to determine how much sodium and potassium your child is eliminating. Children with congenital adrenal hyperplasia eliminate more sodium and less potassium than usual.
Our physicians may recommend a karyotype test for a baby or child with ambiguous genitals. This blood test looks for the presence of an X and a Y chromosome, which indicates your child is a boy, or two X chromosomes, which indicates your child is a girl.
Pelvic Ultrasound Tests
If your newborn child has ambiguous genitals, a doctor may order a pelvic ultrasound and other imaging studies to determine whether the child’s internal sexual organs are male or female. In this test, the doctor places a device called a transducer on your child’s abdomen. The transducer emits high-frequency sound waves that produce a computerized image of the reproductive organs.
Bone Age Studies
Bone age studies, which are X-rays of growth plates in the wrists, hands, and pelvis, may be used to determine if an infant or child has advanced skeletal development for his or her age. These studies can help a doctor monitor growth in children with nonclassic congenital adrenal hyperplasia. They may also be used to monitor treatment in children with the classic form of the condition.