Adrenal gland enlargement was first described by the Napolitan anatomist De Crecchio . The adrenal cortex is formed in the 4th week of gestation, functionally secreting steroids by the 6-7th week of gestation . Biosynthesis of the steroids: cortisol, aldosterone, and androgens from cholesterol occurs under the Adrenocorticotrophic Hormone (ACTH) stimulus with the involvement of five key enzymes : P450scc, 3β-OH dehydrogenase (3β-HSD), 17α -hydroxylase (17α-OH), 21-hydroxylase (21-OH), 11β-hydroxylase (11β-OH) [3,4] .
These steroidogenic enzymes are members of the cytochrome P450 family of oxidases. Congenital Adrenal Hyperplasia (CAH) – is a complex and heterogeneous group of conditions, inherited as Autosomal Recessive (AR) disorders. The resultant deficiencies in one of the five enzymes involved in adrenal steroidogenesis lead to defects in the steroidogenic pathways and biosynthesis of cortisol, aldosterone and androgens. Accumulation of steroid precursors as well as a resulting rise in ACTH levels drives enlargement of the adrenal gland and overproduction of adrenal androgens.
Precursor steroids proximal to the blocked step accumulate and can be shunted into other metabolic pathways, particularly that of androgen biosynthesis. The biochemical and clinical phenotype depends on the specific enzymatic defect and the impairment of specific enzyme activity .
All variants are accompanied with glucocorticoid deficiency but each variant of CAH is characterized by a distinct hormonal milieu reflecting the location of the specific block in the path of steroidogenesis. Defects of the enzymes 21-OH and 11β-OH only affect adrenal steroidogenesis, whereas 17α-OH and 3β-HSD deficiency also impact steroid biosynthesis in the gonads.