Serum concentrations of DHEA, DHEAS, 17α-hydroxyprogesterone, Δ4-androstenedione and testosterone in children determined by TurboFlow-LC–MS/MS

Discrepancy between radioimmunoassay and high performance liquid chromatography tandem-mass spectrometry for the analysis of androstenedione

The discrepancy of results for the quantification of androstenedione in human serum between a radioimmunoassay (RIA) method and high performance liquid chromatography tandem-mass spectrometry (LC-MS/MS) was investigated. RIA overestimated concentrations compared to LC-MS/MS on 59 clinical samples (RIA=1.79×LC-MS/MS+0.94). RIA kit and LC-MS/MS calibrants were also determined by both methods. The RIA performed with improved accuracy on the calibrants (RIA=1.35×LC-MS/MS-0.28). Lipid, protein, electrolyte content, and pH of the two sets of calibrants were further investigated. The RIA calibrants contained little lipid material, while the LC-MS/MS calibrant material contained the same levels expected in normal serum/plasma. The pH and sex hormone binding globulin (SHBG) values were different between the RIA calibrants and the LC-MS/MS calibrant material (SHBG, 31±2 and 38±2nmol/l; pH, 8.27±0.18 and 8.66±0.03, respectively). No correlation was observed between androstenedione RIA and LC-MS/MS discrepancy and lipid or protein. LC-MS/MS sample preparation was tested for the removal of protein-bound material and recovery determined (99-108%). The corresponding RIA results overestimated androstenedione by 52-174% compared to LC-MS/MS. The results here demonstrate that LC-MS/MS is the more accurate method.

Serum levels of insulin-like factor 3, anti-Müllerian hormone, inhibin B, and testosterone during pubertal transition in healthy boys: a longitudinal pilot study

Insulin-like factor 3 (INSL3) is a promising marker of Leydig cell function with potentially high clinical relevance. Limited data of INSL3 levels in relation to other reproductive hormones in healthy pubertal boys exist. In this study, we aimed to evaluate longitudinal serum changes in INSL3 compared with LH, FSH, testosterone, inhibin B, and anti-Müllerian hormone (AMH) during puberty in healthy boys. Ten boys were included from the longitudinal part of the COPENHAGEN Puberty Study. Pubertal evaluation, including testicular volume, was performed and blood samples were drawn every 6 months for 5 years. Serum concentrations of testosterone were determined by a newly developed LC–MS/MS method, and serum concentrations of INSL3, AMH, inhibin B, FSH, and LH respectively were determined by validated immunoassays. The results showed that serum INSL3 levels increased progressively with increasing age, pubertal onset, and testicular volume. In six of the ten boys, LH increased before the first observed increase in INSL3. In the remaining four boys, the increase in LH and INSL3 was observed at the same examination. The increases in serum concentrations of LH, testosterone, and INSL3 were not parallel or in ordered succession and varied interindividually. We demonstrated that INSL3 concentrations were tightly associated with pubertal onset and increasing testicular volume. However, the pubertal increases in LH, INSL3, and testosterone concentrations were not entirely parallel, suggesting that INSL3 and testosterone may be regulated differently. Thus, we speculate that INSL3 provides additional information on Leydig cell differentiation and function during puberty compared with traditional markers of testicular function.

LC–MS/MS in endocrinology: what is the profit of the last 5 years?

Currently, chromatography (GC but more commonly HPLC) is the analytical method of choice for several hormones, either because the immunoassays suffer from extensive crossreactivity or because chromatography permits simultaneous measurements of hormones. However, sometimes the conventional detection systems with HPLC methods do not meet desired specificity. With the increase of robust and affordable LC–MS/MS systems, the next step forward in specificity was taken. LC–MS/MS is rapidly being incorporated in the endocrine laboratories. To be useful in the clinical diagnostic practice, it is of utmost importance that methods are both analytically and clinically vaidated, as until now, the majority of applications of LC–MS/MS in the clinical laboratories are ‘home-made’ methods, therefore special case must be taken. This review aims to focus on Clinical and Laboratory Standards Institute or comparable validated LC–MS/MS methods for targeted hormone analysis used for diagnostic purposes in human samples, published in the last 5 years.