Approach to initial diagnostic testing for nonclassic 21-hydroxylase deficiency

This algorithm summarizes our suggested approach to initial diagnostic testing for nonclassic CAH due to 21OHD. Biochemical testing for nonclassic 21OHD is warranted in any individual with clinical features consistent with 21OHD and in asymptomatic individuals with an affected family member. Common clinical features of nonclassic 21OHD are shown in the inset. This algorithm is intended for use with additional UpToDate content on the diagnosis and management of nonclassic 21OHD in children, adolescents, and adults.

21OHD: 21-hydroxylase deficiency; ACTH: corticotropin; CAH: congenital adrenal hyperplasia.

* If clinical suspicion for nonclassic 21OHD remains high, a cosyntropin (ACTH) stimulation test is the next step, especially if the screening basal 17-hydroxyprogesterone level is >82 ng/dL (2.5 nmol/L) or in the highest quartile of the age-specific reference range.

¶ Most laboratories use mass spectrometry-based assays to measure 17-hydroxyprogesterone. However, if immunoassay was used, additional evaluation is warranted when 17-hydroxyprogesterone values are >1000 to 2000 ng/dL (30 to 61 nmol/L). Additional evaluation includes measuring an ACTH-stimulated 17-hydroxyprogesterone level and/or genotyping of the CYP21A2 gene.

Δ In nonclassic 21OHD, 21-hydroxylase activity is sufficient for adequate cortisol production. In the more severe form of classic 21OHD, cortisol deficiency develops. A serum 17-hydroxyprogesterone value >10,000 ng/dL (300 nmol/L) suggests possible classic 21OHD. ACTH stimulation testing should be performed to diagnose cortisol deficiency. Refer to other UpToDate content on the diagnosis of adrenal insufficiency in children and adults.

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Approach to initial diagnostic testing for nonclassic 21-hydroxylase deficiency