Overdiagnosis of 21-hydroxylase late onset congenital adrenal hyperplasia: correlation of corticotropin test and human leukocyte antigen typing.

OBJECTIVE

To evaluate the reliability of the ACTH test as a means for detection of late onset congenital adrenal hyperplasia (CAH) and discriminating it from polycystic ovary syndrome (PCOS), by repeating the test after 6 months of cyproterone acetate and ethinyl E2 treatment.

DESIGN

Follow-up comparison study.

SETTING

Reproductive Endocrinology in an university tertiary center.

PATIENTS

Thirty-one young women with hirsutism, oligoamenorrhea, and acne, 21 of them detected as late onset CAH, and 10 as non-late onset CAH (PCOS).

INTERVENTION

Cyproterone acetate and ethinyl E2 treatment for > or = 6 months. The ACTH test, before and after 6 months of cyproterone acetate + ethinyl E2 treatment, and human leukocyte antigen (HLA) typing.

MAIN OUTCOME MEASURE

The ACTH test interpretation correlated to HLA typing.

RESULTS

By repeating the ACTH stimulation test in the 31 women (after cyproterone acetate + ethinyl E2 administration), we found a diminution in the rate of accumulation of 17 alpha-hydroxyprogesterone (delta 17-OHP) + P, in all 21-hydroxylase late onset CAH cases. As a result of treatment with cyproterone acetate + ethinyl E2, a decrease in the accumulation rate of 17-OHP + P, below the discriminative value for late onset CAH (6.5 ng/dL per minute), was noted among 12 of 21 women defined primarily as late onset CAH. Among the nine other women, a decrease in the accumulation rate of 17-OHP + P was noted, however not < 6.5 ng/dL per minute.

CONCLUSIONS

The interpretation of delta 17-OHP + P for the diagnosis of late onset CAH may be too sensitive as to the correct clinical diagnosis of late onset CAH. By repeating the ACTH test after 6 months of treatment with cyproterone acetate-ethinyl E2, specificity and accuracy may be improved.