Sex steroid levels in corresponding cerebrospinal fluid and serum samples quantified by mass spectrometry in men

Sex steroids exert important biological functions within the CNS, but the underlying mechanisms are poorly understood. The contribution of circulating sex steroids to the levels in CNS tissue and cerebrospinal fluid (CSF) has been sparsely investigated in human and with inconclusive results. This could partly be due to lack of sensitive validated assays. To address this, we validated a gas chromatography-tandem mass spectrometry (GC-MS/MS) assay for quantification of sex steroid hormones/precursors in CSF.

GC-MS/MS quantification of dihydrotestosterone (DHT, CSF lower limit of quantification, 1.5 pg/mL), testosterone (4.9), estrone (E1, 0.88), estradiol (E2, 0.25), dehydroepiandrosterone (DHEA, 38.4), androstenedione (4D, 22.3), and progesterone (P, 4.2) in CSF, and corresponding serum samples from 47 men.

Analyses of CSF revealed that DHEA was the major sex steroid (73.5 ± 31.7 pg/mL) followed by 4D (61.4 ± 29.6 pg/mL) and testosterone (49.5 ± 18.9 pg/mL). The CSF levels of DHT, E2, and E1 were substantially lower, and P was in general not detectable in CSF. For all sex steroids except E2, strong associations between corresponding CSF and serum levels were observed. We propose that testosteronein CSF is derived from circulating testosterone, DHT in CSF is from local conversion from testosterone, while E2 in CSF is from local conversion from 4D in CNS.

We describe the first thoroughly validated highly sensitive mass spectrometric assay for a broad sex steroid hormone panel suitable for human CSF. This assay constitutes a new tool for investigation of the role of sex steroid hormones in the human CNS.

In this study, a fully validated highly sensitive mass spectrometric assay for sex steroids was applied to human CSF. The results were used to describe the relative contribution of peripheral circulating sex steroids together with locally transformation of sex steroids to the levels in CSF. The results are of importance to understand the biological processes of the human brain.