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Title: 17β-Estradiol and testosterone levels in axillary perspiration of men: Environmental factors, inter- and intra-individual variation
Authors: deCatanzaro, Denys
Elliott, Brittney
Issue Date: Nov-2015
Abstract: In rodents, there is accumulating evidence that sex steroids, particularly estradiol (E2), have pheromonal properties. Male mice actively direct their urine, which contains these hormones in abundance, at proximal females. Radiolabelled E2 injected into male mice has subsequently been found in females that cohabited with these males for a few days, especially in these females’ reproductive systems and brains. Little is known about the potential pheromonal properties of E2 and other sex steroids such as testosterone (T) in humans, however. Previous work from this laboratory found remarkable inter-individual variation in levels of E2 and T in axillary perspiration of men, and levels of E2 and T in the axilla correlated very poorly with levels of the same hormones in other substrates. The axilla has unique histological properties which may allow it to synthesize these hormones de novo. This project aimed to investigate inter- and intra-individual variation in levels of E2 and T in the axillary perspiration of men, and to assess the relationships of various environmental factors to these hormones. Eighty-one males were recruited from the David Braley Athletic Centre at McMaster University and asked to donate four perspiration samples approximately 1-2 weeks apart. Participants were randomly assigned to have the first two sessions conducted by a female researcher and the last two conducted by a male researcher, or vice versa. Participants also filled out, during the first session, a questionnaire assessing various environmental factors which we suspected might be related to axillary sex steroid levels. These factors included dietary phytoestrogen consumption, stress level, relationship status, and recent sexual contact. E2 and T were measured using enzyme-linked immunosorbent assay (ELISA). Overall, levels of both axillary E2 and T were fairly stable within an individual but ranged widely among individuals. E2 and T correlated very strongly with one another (i.e. from the same individual from the same session). A composite score indicating recent romantic/sexual contact with females correlated significantly with an individual’s average axillary E2, but this score did not correlate significantly with average T. However, when the samples conducted by the female researcher and male researcher were considered separately, the composite score correlated significantly with E2 in measures taken by the female researcher, but not in those taken by the male researcher. There was a similar trend, albeit non-significant, between this composite and T in samples taken by the female researcher. A multiple regression analysis was performed using age, a phytoestrogen composite score, a stress composite score, an exercise score, a homosexuality composite score, a composite score of relations with females, and a birth control pill exposure composite score as predictors of axillary E2. This did not show significant prediction when all measures of E2 were considered, but it was significant considering only the measures conducted by the female researcher. Overall, the intra-individual stability noted in levels of axillary E2 and T in men suggests stable inter-individual differences, possibly subserved by genetic factors. However, many other factors, including environmental conditions consistent throughout the duration of this project, may also affect axillary sex steroids. It is possible that contact with proximal females promotes an increase in levels of axillary E2 and T in men. Since these hormones are readily absorbed transdermally, the potential for E2 and T to be transferred via perspiration is worth further investigation.
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