Elevated testosterone levels and social ranks in female rock hyrax

In mammals, males maintain significantly higher testosterone (T, 'the male hormone') levels than females throughout the year and are typically dominant over females. Our study of the cooperatively breeding rock hyrax (Procavia capensis) demonstrated a distinct exception. In most hyrax social groups that we studied, adult females were at the highest social rank within the group and showed higher than or equal T levels to males. To our knowledge, this is the first reported instance of adult female mammals demonstrating higher T levels than adult males. However, although T levels significantly correlated with rank in males, in females such correlations were not detected, suggesting a more complex interplay between behavior and endocrine factors in this species.     

Can hair steroids predict pregnancy longevity?

Maintaining pregnancy to term is important as preterm delivery is a risk factor for impaired infant development, which may have negative long-term consequences. Therefore, developing biomarkers that can predict pregnancy longevity during early gestation is essential for the prevention of preterm birth. Here we explored whether maternal hair testosterone and cortisol, representing the pre-conception and first trimester periods respectively, may be used to predict pregnancy longevity. We recruited 125 pregnant women that contributed hair samples and answered a personal information questionnaire that included pre-conception smoking. We quantified steroids using commercial enzyme-linked immunosorbent assay kits. Gestational age at delivery was obtained from medical records. We used General Linear Models to predict gestation length. The model that included first trimester cortisol, pre-conception smoking, pre-conception testosterone and the interaction between first trimester cortisol and pre-conception smoking predicted 13% of the variance in gestation length (R² = 0.130; n?=?105; p?=? 0.007). First trimester cortisol was the best predictor of gestational length. Women with high levels of cortisol in their first trimester had an increased probability of a full-term delivery. The effect of cortisol was especially pronounced in smokers (ß?=?1.69), compared to non-smokers (ß?=?0.45). Pre-conception testosterone also contributed to the model. Our study suggests that hair steroids may be used to predict pregnancy longevity, together with other contributing factors.