The identification and simultaneous quantification of neuroactive androstane steroids and their polar conjugates in the serum of adult men, using gas chromatography–mass spectrometry

Certain androstane steroids (AS) modulate ionotropic receptors, as do the pregnane steroids. Whereas women produce significant amounts of neuroactive progesterone metabolites, the steroid neuromodulators in men originate mainly from the 3-oxo-4-ene C19-steroids, which are converted to their 3α- and 3β-hydroxy-5α/5β-reduced metabolites. The neuromodulating effects of AS prompted us to monitor circulating levels of the steroids to estimate metabolic pathways in the periphery that may influence brain concentrations of AS. Hence, the serum levels of 20 steroids and 16 steroid polar conjugates including 17-oxo- and 17β-hydroxy-derivatives of 5α/β-androstane-3α/β-hydroxy-androstane steroids were quantified in 15 men (16–62 years of age) using GC–MS. The conjugated AS for the most part reached micromolar concentrations, these being two or three orders of magnitude higher than those of the free steroids. The ratios of conjugates to free steroids were one to two orders of magnitude higher than the values for the corresponding pregnane steroids. This data suggested that conjugation may considerably restrain the transport of free AS from the periphery into the central nervous system.