- Also called:
- adrenogenital syndrome
congenital adrenal hyperplasia
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What is congenital adrenal hyperplasia?
Congenital adrenal hyperplasia (CAH) refers to a group of inherited disorders impacting the adrenal glands, which results from genetic mutations affecting enzymes involved in cortisol production. The most common type is 21-hydroxylase deficiency, leading to excess androgen production and, in severe cases, life-threatening complications shortly after birth.
Females may exhibit virilization, characterized by masculine-appearing genitalia, while males may show precocious sexual development. CAH can also manifest later in life, causing issues such as excess facial hair and infertility in women. Treatment involves hormone replacement and, in some instances, surgery.
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How does congenital adrenal hyperplasia affect the adrenal glands?
Congenital adrenal hyperplasia (CAH) is caused by gene mutations that affect enzymes involved in cortisol production in the adrenal glands. The mutations reduce cortisol production, triggering a compensatory increase in adrenocorticotropin secretion from the anterior pituitary.
Elevated adrenocorticotropin levels may normalize cortisol secretion but also stimulate androgen and mineralocorticoid production in the adrenal cortex. The specific clinical effects of CAH depend on the particular enzyme deficiency. The most common type, 21-hydroxylase deficiency, leads to excess androgen production and, in some cases, decreased aldosterone production.
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What hormones are involved in congenital adrenal hyperplasia?
Congenital adrenal hyperplasia (CAH) involves several hormones due to enzyme deficiencies affecting cortisol production in the adrenal glands. The most common cause is a deficiency in 21-hydroxylase, which leads to decreased cortisol and sometimes aldosterone, and excess adrenal androgens. This hormonal imbalance can cause virilization in females and precocious sexual development in males.
Other rare forms of CAH can result from deficiencies in 11-hydroxylase (leading to virilization and hypertension due to excess deoxycorticosterone), 17-hydroxylase (causing sexual infantilism and hypertension), or 18-hydroxylase (resulting in aldosterone deficiency). A defect in an early step of steroid synthesis can cause congenital lipoid adrenal hyperplasia, leading to deficiencies in glucocorticoids and mineralocorticoids. The specific hormonal profile and clinical manifestations depend on the particular enzyme deficiency.
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What are the main symptoms of congenital adrenal hyperplasia?
Congenital adrenal hyperplasia (CAH) arises from gene mutations affecting adrenal gland cortisol production. The most common form, 21-hydroxylase deficiency, leads to excess androgen production. In newborn girls, this can cause virilization, resulting in masculine-appearing external genitalia.
Other symptoms of CAH include precocious sexual development in boys, decreased aldosterone production, increased urinary excretion of sodium and water, decreased urinary excretion of potassium, low blood pressure, low serum sodium concentrations (hyponatremia), and high serum potassium concentrations (hyperkalemia). In women, late-onset CAH can cause excess facial hair, infrequent menstruation, and infertility.
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How does a genetic problem cause congenital adrenal hyperplasia?
Congenital adrenal hyperplasia (CAH) arises from genetic mutations affecting enzymes crucial for cortisol production in the adrenal glands. These mutations, varying from single nucleotide changes to entire gene deletions, lead to decreased cortisol synthesis.
The body responds by increasing adrenocorticotropin secretion from the anterior pituitary, which attempts to restore cortisol levels. However, this also stimulates excessive androgen production and, in some cases, mineralocorticoids, leading to various clinical manifestations depending on the specific enzyme deficiency. CAH is inherited as an autosomal recessive trait, requiring both parents to pass on the defective gene for the disorder to manifest.
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How do doctors diagnose and treat congenital adrenal hyperplasia?
Congenital adrenal hyperplasia (CAH) diagnosis involves genetic testing, such as prenatal screening, to identify gene mutations that cause the disorder. After birth, CAH is diagnosed through hormone and enzyme level analysis.
Treatments include synthetic glucocorticoids like prednisone or cortisol to reduce adrenal androgen production, and mineralocorticoids if needed. Surgery may be necessary for girls to correct labial fusion and reduce clitoris size.
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congenital adrenal hyperplasia, any of a group of inherited disorders that are characterized by enlargement of the adrenal glands resulting primarily from excessive secretion of androgenic hormones by the adrenal cortex. It is a disorder in which the deficiency or absence of a single enzyme has far-reaching consequences.
Genetic causes
Congenital adrenal hyperplasia mainly affects infants and is inherited as an autosomal recessive trait, meaning that it is not manifested unless the trait is inherited from both parents. The disorder is caused by any of several mutations in the genes encoding enzymes that are involved in the production of cortisol by the adrenal glands. The mutations vary from a single change in one of the nucleotide bases that constitute the gene to the deletion of the entire gene. The result of these mutations is a decrease in cortisol production. As a consequence, there is a compensatory increase in the secretion of an anterior pituitary hormone known as adrenocorticotropin. The high levels of adrenocorticotropin may restore cortisol secretion to near normal; however, they also stimulate the production of androgen and sometimes mineralocorticoids (hormones that stimulate retention of salt and water by the kidneys) by the adrenal cortex. The exact pattern and clinical manifestations of the disorder depend on the particular enzyme deficiency.
Types and clinical manifestation
The most common type of congenital adrenal hyperplasia is deficiency of 21-hydroxylase, an enzyme that catalyzes the next-to-last step in the synthesis of cortisol. In infants with partial 21-hydroxylase deficiency, the production of cortisol is near normal, but there is excess production of adrenal androgens. Excess androgen produced to overcome this deficiency during fetal life results in virilization—the development of masculine-appearing external genitalia in newborn girls and precocious sexual development in boys—that becomes prominent as the child grows. There may also be decreased production of aldosterone, which leads to increased urinary excretion of sodium and water and decreased urinary excretion of potassium, resulting in low blood pressure, low serum sodium concentrations (hyponatremia), and high serum potassium concentrations (hyperkalemia). Severe 21-hydroxylase deficiency becomes evident soon after birth and may be fatal if not recognized and treated promptly.
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The clinical manifestations of excess androgen production in utero that affect newborn genetic females include an enlarged clitoris, which may be mistaken for a penis; an enlarged vulva, which resembles a bilobed scrotum; and partial or complete fusion of the labia majora, with the opening of the urethra at the base of the clitoris. If not diagnosed early in life, girls with severe congenital adrenal hyperplasia, known as female pseudohermaphrodites, may be raised as boys and live thereafter as short, muscular men. These individuals are infertile and have only vestigial ovaries. There has been much debate as to whether genetic females who have been raised as boys can, when diagnosed late in childhood or in adolescence, assume the sexual identity of women. It appears that at least in some instances this is possible. Affected genetic males are more normal in appearance but may have penile enlargement. Continued excess androgen production in both girls and boys leads to rapid growth in the first years of life. However, the androgens also stimulate maturation and closure of the epiphyseal centres of bones so that linear growth ceases well before the usual age of puberty. The frequency of 21-hydroxylase deficiency varies widely in different regions of the world, from as high as 1 in 300 births to lower than 1 in 20,000 births. Because the postnatal consequences are so severe, 21-hydroxylase deficiency is sometimes tested for as part of newborn screening programs.
Other, rarer forms of congenital adrenal hyperplasia result in varying degrees of hypertension or lack of sexual development, depending on the particular enzyme that is defective. Deficiency of 11-hydroxylase, an enzyme that catalyzes the last step in the synthesis of cortisol, leads to virilization and hypertension, the latter of which is caused by excess production of deoxycorticosterone, a mineralocorticoid similar to aldosterone. Deficiency of 17-hydroxylase leads to deficiency of estrogens and androgens and to excess deoxycorticosterone, causing sexual infantilism and hypertension. Congenital lipoid adrenal hyperplasia is caused by a defect in a very early step in the steroid synthetic pathway that results in glucocorticoid and mineralocorticoid deficiency and failure of development of secondary sex characteristics. Another genetic defect, 18-hydroxylase deficiency, results in aldosterone deficiency.
Congenital adrenal hyperplasia also occurs in adolescents and adults, in which case it is referred to as late-onset congenital adrenal hyperplasia. In women it results primarily in excess growth of facial hair, decreased frequency or cessation of menstrual periods, and infertility. In contrast, the effects are minimal in men because androgen production by the testes far exceeds adrenal androgen production, even when the latter is excessive.
Treatment
Infants with congenital adrenal hyperplasia are treated with cortisol or a synthetic glucocorticoid, such as prednisone or dexamethasone, and a mineralocorticoid if necessary. Glucocorticoids inhibit adrenocorticotropin secretion, resulting in decreased production of adrenal androgens. However, it can be difficult to control the excess production of adrenal androgens without causing symptoms and signs of cortisol excess (iatrogenic or physician-induced Cushing syndrome). Girls may need surgery to correct labial fusion and to reduce the size of the clitoris. Infants treated appropriately soon after birth have a normal growth rate, undergo normal puberty, and are fertile.
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Patients of any age with congenital adrenal hyperplasia are treated with cortisol or a synthetic hormone with similar properties, such as prednisone; some patients may also require mineralocorticoid treatment.