The Simultaneous measurement of serum testosterone and 5α-dihydrotestosterone by gas chromatography-mass spectrometry (GC-MS).

BACKGROUND: Simultaneous measurement of testosterone (T) and 5α-dihydrotestosterone (DHT) is important for diagnosing androgen deficiency states and hyperandrogenism in males and females, respectively. However, immunoassays used for T and DHT determination suffer from inadequate specificity and sensitivity, while tandem mass spectrometry is expensive and demanding in use. METHODS AND RESULTS: We developed a selective gas chromatography-mass spectrometry (GC-MS) method for parallel T and DHT measurement. The assay showed a linear response up to 46.5nmol/L, intra- and interassay imprecision and inaccuracy <15% and recoveries in spiked samples >90% for both analytes. The limit of quantitation was 0.117nmol/L for T and 0.168nmol/L for DHT. Comparison with immunoassays revealed good agreement for T in males, but a bias in favour of immunoassays at low concentrations for T in females and DHT in both sexes. We established reference ranges for T and DHT and suggest interval partitioning for T according to age in men and menstrual cycle in women. Assay validation in a clinical setting suggests that measuring DHT or T/DHT ratio may help identify patients with polycystic ovary syndrome. CONCLUSION: We developed a selective, simple and inexpensive GC-MS method for parallel measurement of T and DHT with potential use in the clinical laboratory.

Establishing reference intervals for sex hormones on the analytical platforms Advia Centaur and Immulite 2000XP.

Reliable reference intervals for sex hormones are indispensable in evaluations of the hypothalamo-pituitary-gonadal axis. This study established reference intervals for estradiol, progesterone, luteinizing hormone, follicle-stimulating hormone, and prolactin with the immunoassay platforms Advia Centaur and Immulite 2000XP (Siemens Healthcare, Germany). We recruited healthy men (n=220), women in the follicular (n=139) or luteal (n=87) phases of the menstrual cycle, and postmenopausal women (n=103). Data was analyzed according to CLSI EP28-A3c guidelines. Although reference intervals established with both platforms showed good agreement with ranges quoted by the assay manufacturer, two discrepancies were noted. First, intervals for prolactin in women were influenced by hormonal status, and the partition analysis supported their separation into subgroups based on menstrual cycle. Second, the upper limit for estradiol in the follicular phase was nearly a half of that provided by the manufacturer. This discrepancy was attributed to the stringent definition of the follicular phase (consistently set at days 3-5 after menstruation onset). Our findings suggest that reference values for prolactin should both be gender specific and account for menstrual cycle phase. The results also emphasize that clear-cut selection criteria are required when assembling populations for establishing endocrine reference intervals.