Endocrine Abstracts

Objective: Immunoassays of steroids are still used in the diagnosis and biochemical monitoring of patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency (21 OHD). However, high levels of steroid intermediates can promote cross-reactivity between steroids giving rise to falsely elevated levels.

Design: Fifty-nine patients with classic 21OHD (38 women) were studied. Blood samples were collected in the morning after overnight medication fasting. Immunoassay and liquid chromatography-tandem mass spectrometry (LC-MS/MS) quantitation of the following steroids were performed: 17OH-progesterone (17OH), 21-deoxycortisol (21DF, an 11-hydroxylated derivative of 17OHP), 11-deoxycortisol, testosterone and androstenedione.

Results: Concentrations of testosterone, androstenedione and 17OHP were lower when measured with LC-MS/MS compared with immunoassays, with exception of testosterone levels in men. Testosterone results differed by 30.0% in females and only a small difference in men (+1.1%). The difference was even larger for androstenedione (31.3%) and 17OHP (57.0%).

The correlation between 21DF and 17OHP was good (r=0.87), but three patients did not have measurable 21DF which indicate that 21DF is not superior to 17OHP to monitor replacement therapy. Subjects with no enzyme activity had significantly lower mean 11-deoxycortisol concentrations compared with subjects with severe enzyme failure, analyzed by LC-MS/MS. Levels of other steroid hormones did not differ significantly between the genotypes and methods.

Conclusions: LC-MS/MS is superior to immunoassays in monitoring patients with 21-OHD on corticosteroid replacement therapy as they are more specific and can be multiplexed. Immunoassays seems to overestimate high levels of 17OHP and androstenedione considerably.