Comparison of assay methods for quantifying sex hormone concentrations across the menstrual cycle in rhesus macaques

Immunoassays have been the preferred method for steroid hormone analysis for more than 50 years. Automated immunoassays (AIAs) offer high-throughput, rapid data turnaround, and low cost for measuring steroid hormone concentrations. The application of liquid chromatography-tandem mass spectrometry (LC-MS/MS) for steroid quantification provides greater specificity and selectivity for individual steroids, the ability to simultaneously analyze multiple steroids, and high-throughput and automation. We compared AIA and LC-MS/MS for analysis of 17β-estradiol (E2) and progesterone (P4) over the course of several menstrual cycles in 12 rhesus macaques (Macaca mulatta). Serum samples were collected every four days across four menstrual cycles from each monkey. AIAs were performed on a Roche cobas e411 analyzer. Analysis of E2 and P4 was performed by LC-MS/MS on a Shimadzu-Nexera-LCMS-8060 instrument. Scatter plots with Passing-Bablok regression showed excellent agreement between AIA and LC-MS/MS for both E2 and P4. Bland-Altman plots revealed no bias for either method; however, AIA overestimated E2 at concentrations >140 pg/ml and underestimated P4 at concentrations >4 ng/ml compared to LC-MS/MS. A comparison of testosterone (T) concentrations measured by AIA and LC-MS/MS in the same samples was also performed. In contrast to E2 and P4, AIA and LC-MS/MS yielded significantly different results for T concentrations, with AIA consistently underestimating concentrations relative to those obtained by LC-MS/MS. Well-characterized AIAs are an excellent tool for daily monitoring of monkey menstrual cycles or providing single data points requiring fast turnaround. In certain situations where AIA may provide inaccurate estimations of E2 and P4 concentrations, LC-MS/MS assays are preferable.

Labeled oxytocin administered via the intranasal route reaches the brain in rhesus macaques

Oxytocin may have promise as a treatment for neuropsychiatric disorders. Its therapeutic effect may depend on its ability to enter the brain and bind to the oxytocin receptor. To date, the brain tissue penetrance of intranasal oxytocin has not been demonstrated. In this nonhuman primate study, we administer deuterated oxytocin intranasally and intravenously to rhesus macaques and measure, with mass spectrometry, concentrations of labeled (exogenously administered) and endogenous oxytocin in 12 brain regions two hours after oxytocin administration. Labeled oxytocin is quantified after intranasal (not intravenous) administration in brain regions (orbitofrontal cortex, striatum, brainstem, and thalamus) that lie in the trajectories of the olfactory and trigeminal nerves. These results suggest that intranasal administration bypasses the blood-brain barrier, delivering oxytocin to specific brain regions, such as the striatum, where oxytocin acts to impact motivated behaviors. Further, high concentrations of endogenous oxytocin are in regions that overlap with projection fields of oxytocinergic neurons.

Simultaneous quantitation of multiple contraceptive hormones in human serum by LC-MS/MS

OBJECTIVE

The objective was to develop a method to simultaneously quantify five commonly used hormonal contraceptives (HCs) and two endogenous sex steroids by liquid chromatography-tandem triple quadrupole mass spectrometry (LC-MS/MS) and apply this method to human serum samples.

STUDY DESIGN

We developed a method to simultaneously analyze ethinyl estradiol (EE2), etonogestrel (ENG), levonorgestrel (LNG), medroxyprogesterone acetate (MPA) and norethisterone (NET), along with estradiol (E2) and progesterone (P4), in human serum for a Shimadzu Nexera-LCMS-8050 LC-MS/MS platform. We analyzed serum collected from women self-reporting use of oral contraceptives, contraceptive implants or injectable contraceptives (n=14) and normally cycling women using no HC (n=15) as well as pooled samples from women administered various HCs (ENG, n=6; LNG, n=14; MPA, n=7; NET, n=5).

RESULTS

Limits of quantitation were 0.010ng/mL for E2, EE2 and P4; 0.020ng/mL for ENG, LNG and MPA; and 0.040ng/mL for NET. Precisions for all assays, as indicated by coefficient of variation, were less than or equal to 12.1%. Accuracies for all assays were in the range of 95%-108%. Endogenous hormone values obtained from analysis of human serum samples are in agreement with levels previously reported in the literature for normally cycling women as well as for women taking the appropriate HC.

CONCLUSIONS

We have developed a robust, accurate and sensitive method for simultaneously analyzing commonly used contraceptive steroids and endogenous sex steroids in human serum.

IMPLICATIONS

This analytical method can be used for quantitating contraceptive steroid levels in women for monitoring systemic exposure to determine drug interactions, nonadherence, misreporting and proper dosing.