Measurement of the cortisol production rate in two sisters with 17α-hydroxylase deficiency using [1,2,3,4- 13C]cortisol and isotope dilution mass spectrometry

Abstract

[1,2,3,4- 13C]cortisol was i.v. administered to two sisters aged 11 yr (patient I) and 3 yr (patient II) who suffer from 17α-hydroxylase deficiency. This is the first time that the cortisol production rate (CPR) in patients with 17α-hydroxylase deficiency has been measured with a stable labelled tracer using the urinary method. The urine was collected for 3 days. High-performance liquid chromatography (HPLC) of ≈100 ml urine extracts was carried out to isolate the small amount of cortisol metabolites excreted. The cortisol metabolites were oxidized to 11-oxo-aetiocholanolone. The isotope dilution in the methyl oxime tert-butyldimethylsilyl ether derivatives was measured by selected ion monitoring gas chromatography/mass spectrometry (GC/MS). The CPR calculated from tetrahydrocortisone (THE) and the cortolones was 765 and 536 nmol/day, respectively in patient I. The CPR in patient II was only calculated from THE and was 62 nmol/day. If radioactive labelled cortisol had been used, much larger quantities of urine would have been needed for isolation of sufficient mass of metabolites, even then purification may have been difficult. Steroid profiling of 1 ml urine samples by GC and identification by GC/MS revealed high concentrations of pregnenolone, progesterone, 11β-hydroxy progesterone and corticosterone metabolites. Tetrahydrocorticosterone and 5α-tetrahydrocorticosterone were found in urine at elevated excretions of 2.5 and 5.7, 0.9 and 2.0 μmol/24h, in patients I and II respectively. No cortisol metabolites were detected by routine GC or GC/MS as the low amounts excreted co-eluted with the relatively abundant corticosterone metabolites.