Basal 17-hydroxyprogesterone cannot accurately predict nonclassical congenital adrenal hyperplasia in children and adolescents

Aim: This study explored whether using the suggested diagnostic serum basal level of 17-hydroxyprogesterone (6.0 nmol/L) would lead to underdiagnosis of nonclassical congenital adrenal hyperplasia. Methods: We retrospectively studied 123 patients with nonclassical congenital adrenal hyperplasia, defined as an adrenocorticotropic hormone-stimulated 17-hydroxyprogesterone level of more than 45 nmol/L. Of these 13 had basal 17-hydroxyprogesterone levels of less than 6.0 nmol/L and 110 exceeded that level. The 42 controls had idiopathic premature pubarche. Clinical and laboratory data were reviewed and compared. Results: There were no differences between patients with 17-hydroxyprogesterone levels of <6.0 nmol/L or ≥6.0 nmol/L based on age at presentation, gender, anthropometric measurements, bone age advancement, age at glucocorticoid initiation and hydrocortisone dosage. Patients with basal 17-hydroxyprogesterone <6.0 nmol/L had significantly lower stimulated 17-hydroxyprogesterone levels (p = 0.02) and higher stimulated serum cortisol levels (p < 0.008). Children with nonclassical congenital adrenal hyperplasia and premature pubarche were clinically indistinguishable from controls with idiopathic premature pubarche. Androgen levels were significantly higher in the nonclassical congenital adrenal hyperplasia group. Conclusion: A basal 17-hydroxyprogesterone threshold of 6.0 nmol/L was not a sensitive predictive marker for diagnosing nonclassical congenital adrenal hyperplasia. Children whose clinical presentation suggests nonclassical congenital adrenal hyperplasia should undergo diagnostic adrenocorticotropic hormone stimulation testing.