[1][2] As a result, higher levels of 17α-hydroxypregnenolone appear in the blood with adrenocorticotropic hormone (ACTH) challenge, which stimulates adrenal corticosteroid synthesis.

3β-HSD II mediates three parallel dehydrogenase/isomerase reactions in the adrenals that convert Δ4 to Δ5 steroids: pregnenolone to progesterone, 17α-hydroxypregnenolone to 17α-hydroxyprogesterone, and dehydroepiandrosterone (DHEA) to androstenedione.

[citation needed] However, complexity arises from the presence of a second 3β-HSD isoform (HSD3B1) coded by a different gene, expressed in the liver and placenta, and unaffected in 3β-HSD-deficient CAH.

[citation needed] In an XX (genetically female) fetus, elevated amounts of DHEA can produce moderate virilization by conversion in the liver to testosterone.

[citation needed] The extent to which mild 3β-HSD CAH can cause early appearance of pubic hair and other aspects of hyperandrogenism in later childhood or adolescence is unsettled.

[citation needed] Undervirilization of genetic males with 3β-HSD CAH occurs because synthesis of testosterone is impaired in both adrenals and testes.

[citation needed] If the infant boy is only mildly undervirilized, the hypospadias can be surgically repaired, testes brought into the scrotum, and testosterone supplied at puberty.

Male sex can be assigned and major reconstructive surgery done to close the midline of the perineum and move the testes into a constructed scrotum.

These severe, classical forms can be observed at birth by the following symptoms: boys may not develop masculine characteristics fully, while girls may have an enlarged clitoris.