Congenital adrenal hyperplasia laboratory tests

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]

Overview

Laboratory Findings

obtaining an early morning baseline serum 17-OHP in symptomatic individuals.

obtaining a complete adrenocortical profile after a cosyntropin stimulation test to differentiate 21-hydroxylase deficiency from other enzyme defects and to make the diagnosis in borderline cases.

genotyping only when results of the adrenocortical profile after a cosyntropin stimulation test are equivocal.

The diagnosis of 21-hydroxylase deficiency is based on measuring 17-OHP

elevated 21-deoxycortisol, androstenedione, and testosterone Elevated plasma renin activity reduced ratio of aldosterone to PRA indicate impaired aldosterone synthesis and can differentiate salt wasters from simple virilizers.

ACTH the gold standard for diagnosis. ACTH stimulation testing is not necessary in children with a basal 17-hydroxyprogesterone less than 82 ng/dL (2.5 nmol/L). However, follow-up ACTH stimulation testing should be performed in children whose baseline values fall between 82 and 200 ng/dL (2.5 to 6 nmol/L) and should be considered to confirm the diagnosis for values greater than 200 ng/dL (6 nmol/L).

In adult women, the diagnosis of NCCAH is strongly suggested by a basal 17-hydroxyprogesterone value greater than 200 ng/dL (6 nmol/L) and confirmed with an ACTH stimulation test.

Serum 17-hydroxyprogesterone value exceeding 1500 ng/dL (43 nmol/L) [5,6]

confirms the diagnosis. Rarely, stimulated values at 60 minutes in affected patients range between 1000 ng/dL (30 nmol/L) and 1500 ng/dL (43 nmol/L) 

genotyping is recommended if stimulated values are in this range.

When a lower post-ACTH cutoff for 17-hydroxyprogesterone (>1000 ng/dL) is used, the false-positive rate is

17-hydroxyprogesterone >1500 ng/dL (43 nmol/L) after ACTH stimulation confirms the diagnosis. For patients with equivocal results (values between 1000 ng/dL [30 nmol/L] and 1500 ng/dL [43 nmol/L]), we perform genotyping to distinguish between a heterozygote carrier and an affected patient.

●The biochemical criteria used for diagnosis in men are the same as those used for women [13].

The biochemical findings in patients with classic 21-hydroxylase deficiency are more severe. Untreated patients with classic congenital adrenal hyperplasia (CAH) have basal 17-hydroxyprogesterone concentrations greater than 3500 ng/dL (105 nmol/L) [1],

[3,4].

reveal the IVS2 mutation, which is seen in both salt-wasters and non-salt-wasters (15, 113, 114).

Compound heterozygotes for two different CYP21A2 mutations usually have a phenotype compatible with the milder mutation.

Heterozygotes have slightly elevated 17-OHP levels after ACTH stimulation, Identifying heterozygote carriers — If it is important to document the presence of a carrier state for genetic counseling, CYP21A2 genotyping should be performed. There is no clear consensus as to whether heterozygote carriers are at increased risk of developing hyperandrogenic symptoms. In several studies of women with hirsutism, 8 to 13 percent were identified as carriers [20-22], similar to the rate seen in nonhirsute women in two of the studies [21,22]. However, no relative with a single mutation was clinically symptomatic in another study of 242 subjects [17].

References


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