Abstract
The concentrations of testosterone deposited in hair during hair growth may provide a retrospective reflection of the concentrations of bioactive testosterone in plasma. The objective of this study was to develop a radioimmunoassay with a sufficiently low limit of detection to measure the testosterone-like immunoreactivity in smaller hair samples (5 mg) than used in earlier studies, and to compare three different extraction procedures. The competitive radioimmunoassay consisted of a polyclonal antiserum (immunogen testosterone-7α-BSA) and a radioligand synthesised from testosterone-3-CMO-histamine. The within-assay and total coefficients of variation in the working range was 3% and 4.5%, respectively. The limit of detection was 0.87 pg/mL, which is equivalent to 0.12 pg/mg testosterone in 5 mg of hair. The concentration of testosterone-like immunoreactivity in hair samples was 1.23 (SD 0.47) pg/mg in women and 2.67 (SD 0.58) pg/mg in men (pulverised hair). Significantly improved precision was found when pulverised hair was used compared to non-pulverised hair. Our data indicate that pulverisation of the hair prior to hormone extraction is crucial. Detection limits fit for the intended purpose are achievable with 5 mg samples of hair.
Highlights
The main biological effects of sex hormones are dependent on their long term concentrations in the tissues, which is one of the reasons why repeated blood sampling is a prerequisite for diagnosing hypogonadism[1]
The RIA developed in the present study enables measurement of testosterone-like immunoreactive molecules in 5 mg samples of hair – a smaller sample amount than earlier reported
The objective of this study was to develop a RIA with a sufficiently low limit of detection to measure the testosterone-like immunoreactivity in both women and men, in smaller hair sample amounts (5 mg) than previously used, and to compare three different hair extraction procedures
Summary
The main biological effects of sex hormones are dependent on their long term concentrations in the tissues, which is one of the reasons why repeated blood sampling is a prerequisite for diagnosing hypogonadism[1]. In the current study we examine the effects of sex and the disintegration of the hair (during the extraction process) on the concentrations of testosterone-like immunoreactivity in hair. The rationale for this is that we expect the biological difference between men and women to overshadow any other physiological or circumstantial sources of variation that could affect the androgenic hormone concentrations in hair. The objective of this study was to develop a RIA with a sufficiently low limit of detection to measure the testosterone-like immunoreactivity in both women and men, in smaller hair sample amounts (5 mg) than previously used, and to compare three different hair extraction procedures. Our primary aim when comparing extraction procedures was to explore the effect on the measurement precision expressed as the relative standard deviation (RSD) of triplicate samples from each individual
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