Endocrine Abstracts

Hormonal male contraceptives suppress gonadotropin secretion to induce azoospermia. These also markedly reduce the testicular production of testosterone. To prevent hypogonadism, pharmaceutical preparations of testosterone therefore need to be administered as a replacement therapy. Peripheral testosterone concentrations thus reflect the exogenous hormone rather than testicular production. However because the testis contributes approximately 95% of epitestosterone (E) production, measurement of plasma and urinary E allows assessment of the degree of suppression of testicular steroidogenesis.

To measure accurately serum E concentrations, a method employing liquid chromatography/tandem mass spectrometry (LC/MS-MS) was developed. To enhance analytical sensitivity, keto-steroids (including E) from extracted serum (0.5 mL) were derivatised to form Girard P hydrazones with a permanent positive charge. The LC system (C8 column −5 μm; gradient elution mixture of water and methanol containing ammonium acetate) was coupled, via an electrospray ionisation source (positive ionisation), to a triple quadrupole tandem MS. The molecular ion was chosen as the precursor for the transition m/z 422 to 343. The lower limit of detection was 0.1 nmol/L.

In eugonadal men (n=13), the mean (SEM) E concentration was found to be 0.32 (0.04) nmol/L (range 0.1 to 0.6–nmol/L), the results agreeing reasonably well with that produced by gas chromatography/MS following extensive sample preparation (1). These preliminary data indicate that serum E concentration in eugonadal men is much lower than the 1 to 2 nmol/L measured by immunoassay (2,3). The future challenge is to gain even greater analytical sensitivity to enable assessment of the degree of suppression of testicular steroidogenesis in males using hormonal contraception.