Changes in the concentration of testosterone in serum during the menstrual cycle, as determined by liquid chromatography.

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Abstract
We used a newly developed high-performance liquid chromatographic (HPLC) method to determine the concentration of testosterone in serum from women and compared the results with those obtained by conventional radioimmunoassay. We used a conventional silica gel column and organic solvent mixture (ethanol plus n-hexane containing a small amount of water). The detection limit for testosterone was as low as 0.2 micrograms/L, sufficient to correctly determine the concentration of the hormone in serum from women. For the calibration curve, we plotted the peak-height ratio of testosterone to 19-nortestosterone. The menstrual-cycle-related rhythm of the concentration of testosterone in serum was related to follicular and luteal phase-shifting, the concentration being considerably greater in the luteal phase than in the follicular phase. In contrast, RIA showed only minor and irregular fluctuation in the concentrations of the hormone throughout the menstrual cycle. When we used the HPLC to measure the hormonal change in a woman with an irregular menstrual cycle, we found that her testosterone concentration increased abnormally early after menstruation.