To Örebro University

Background: It has not yet been established whether men in heterosexual relationships adapt their hormone levels to their female partner's menstrual cycle to allocate reproductive resources to the period when the female is actually fertile.

Aim: This prospective observational study tested the hypothesis that some males have peaks in testosterone or acne (a possible biomarker for androgen activity) near their partners' ovulation, whereas other males display the opposite pattern.

Methods: 48 couples supplied menstrual cycle data, male salivary samples, and a protocol of daily activities for 120 days. Daily saliva samples were analyzed for testosterone concentrations by enzyme-linked immunosorbent assay. The main hypothesis was tested by analyzing whether each individual male's testosterone/acne response to ovulation (either an increase or a decrease in comparison to the individual's average levels) was stable over time. To do this, we analyzed the Spearman correlation between individually normalized periovulatory testosterone and acne during the first half of the study versus the second half of the study.

Outcomes: Correlation between each male individual's periovulatory testosterone and acne patterns during the first half of the study versus the second half of the study.

Results: No predictability in the male individuals' testosterone (Spearman's rho = -0.018, P = .905) or acne (Spearman's rho = -0.036, P = .862) levels during ovulation was found.

Clinical translation: The study being "negative," there is no obvious translational potential in the results.

Strengths and limitations: The main strength of this study lies in the excellent compliance of the study participants and the large number of sampling timepoints over several menstrual cycles, thereby allowing each male individual to be his own control subject. A limitation is that samples were only obtained in the morning; however, including later timepoints would have introduced a number of confounders and would also have hampered the study's feasibility.

Conclusions: The current results strongly indicate that male morning testosterone levels neither increase nor decrease in response to the partner's ovulation. This discordance to previous laboratory studies could indicate either that (i) the phenomenon of hormonal adaptation of men to women does not exist and earlier experimental studies should be questioned, (ii) that the phenomenon is short-lived/acute and wanes if the exposure is sustained, or (iii) that the male testosterone response may be directed toward other women than the partner. Copyright (C) 2018, The Authors. Published by Elsevier Inc. on behalf of the International Society for Sexual Medicine.