<unk>  results from mutations of genes for enzymes mediating the biochemical steps of production of mineralocorticoids, glucocorticoids, or sex steroids from cholesterol by the adrenal glands (steroidogenesis). Each form of<unk>  is associated with a specific defective gene. The most common type (95% of cases) involves the gene for 21-hydroxylase, which is found on 6p21.3 as part of the HLA complex; 21-hydroxylase deficiency results from a unique mutation with two highly homologous near-copies in series consisting of an active gene (CYP21A2) and an inactive pseudogene (CYP21A1P). Mutant alleles result from recombination between the active and pseudogenes (gene conversion). About 5% of cases of<unk>  are due to defects in the gene encoding 11β-hydroxylase and consequent 11β-hydroxylase deficiency. Other, more rare forms of<unk>  are caused by mutations in genes, including HSD3B2 (3β-hydroxysteroid dehydrogenase 2), CYP17A1 (17α-hydroxylase/17,20-lyase), CYP11A1 (P450scc; cholesterol side-chain cleavage enzyme), STAR (steroidogenic acute regulatory protein; StAR), CYB5A (cytochrome b5), and CYPOR (cytochrome P450 oxidoreductase; POR). Expressivity Further variability is introduced by the degree of enzyme inefficiency produced by the specific alleles each patient has. Some alleles result in more severe degrees of enzyme inefficiency. In general, severe degrees of inefficiency produce changes in the fetus and problems in prenatal or perinatal life. Milder degrees of inefficiency are usually associated with excessive or deficient sex hormone effects in childhood or adolescence, while the mildest forms of<unk>  interfere with ovulation and fertility in adults.
Congenital adrenal hyperplasia
Polycystic ovary syndrome
Lipoid congenital adrenal hyperplasia
Late onset congenital adrenal hyperplasia
Persistent adrenarche syndrome
Congenital iodine deficiency syndrome
Congenital hypothyroidism
Congenital hyperinsulinism