Mothers have lower testosterone than non-mothers: evidence from the Philippines.

Testosterone (T) is lower among fathers and men in committed relationships, suggesting that the hormone mediates the trade-off between mating and parenting effort. The function of T in women and responses of the hormone to relationships or motherhood are less well understood. Here we report relationships between T and pairbonding and motherhood in a random sample of 67 women (20.9 to 22.4 years old) participating in a population-based birth cohort study in the Philippines. Testosterone was measured in saliva collected at bedtime and at waking the following morning to capture circadian dynamics. Compared to non-mothers and non-pairbonded women, mothers and pairbonded women had 32% (p<0.0001) and 23% (p<0.004) lower waking T, respectively, but similar evening T. The lower waking T in mothers largely reflected reduced T in mothers of young offspring (<2 years), with mothers of older offspring (2+ years) having intermediate T. These differences were independent of measures of breastfeeding, contraceptive pill use, menstrual cycle, sleep quality, education, employment, and socioeconomic status. Our findings highlight a similar relationship between parenting and committed relationships and T in women as documented in men and suggest that caregiving of dependent young may modulate female T. Future research should clarify whether this cross-sectional association reflects a suppressive effect of motherhood on T, whether these relationships vary across cultures, and the role of T within the endocrine architecture regulating female reproductive and caregiving strategies.