Endogenous and exogenous testosterone levels after administration of deuterium-labelled testosterone propionate in hypogonadotropic hypogonadism.

A gas chromatography-mass spectrometry-selected ion monitoring technique was employed to determine simultaneously the plasma concentrations of endogenous and exogenous testosterone in three patients with hypogonadotropic hypogonadism after a single i.m. dose of testosterone propionate-19,19,19-d3. The plasma levels of testosterone-19,19,19-d3 derived from testosterone propionate-19,19,19-d3 were maintained above the normal testosterone levels (greater than 4 ng/ml) for 48 h, while the plasma levels of endogenous testosterone changed little.