Profiling steroid hormones in amniotic fluid of midpregnancy by routine stable isotope dilution/gas chromatography-mass spectrometry: Reference values and concentrations in fetuses at risk for 21-hydroxylase deficiency

Using routine stable isotope dilution/gas chromatography-mass spectrometry, 17-hydroxyprogesterone, androstenedione, testosterone, dehydroepiandroster one, androstanediol, and 5 alpha-dihydrotestosterone have been profiled in amniotic fluid of midgestation in 77 normal fetuses and 38 untreated or dex amethasone-treated fetuses at risk for 21-hydroxylase deficiency. Dexametha sone was suspended. 5-7 days before amniocentesis. In normal fetuses, amnio tic fluid concentrations (median, range; nanograms per mt) of 17-hydroxypro gesterone did not reveal a sex difference (1.48, 0.21-4.96), whereas those of androstenedione were lower in females (0.53, 0.00-2.71) than in males (0 .93, 0.29-1.98). Testosterone levels were higher in males (0.24, 0.00-0.50) than in females (0.00, 0.00-0.27). No sex difference was found for dehydro epiandrosterone (0.47, 0.19-1.77). Levels of androstanediol and 5a-dihydrot estosterone were below the detection limit of our method in most cases. Reg arding prenatal diagnosis of 21-hydroxylase deficiency. 17-hydroxyprogester one and androstenedione presented the diagnostically most valuable steroids and were of equal diagnostic potential. They permitted successful diagnosi s in 36 of 37 fetuses at risk: 12 were untreated and unaffected, 13 were tr eated and unaffected, 4 were untreated and affected (3 salt wasters and 1 s imple virilizer), and 8 were treated and affected (5 salt wasters and 3 sim ple virilizers). In the latter group, one simple virilizer revealed normal steroid concentrations. Isotope dilution/gas chromatography-mass spectromet ry, providing the highest specificity in steroid analysis, is proposed for routine use in clinical steroid analysis whenever maximal reliability is re quested. Our study provides the first mass spectrometric reference data on amniotic fluid steroid concentrations and underscores the high accuracy of prenatal hormonal diagnosis of 21-hydroxylase deficiency.