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Objectives An energetically demanding environment like a wilderness expedition can lead to potent stressors on human physiology and homeostatic balance causing shifts in energy expenditure and body composition. These shifts likely have consequences on overall health and performance and may potentially differ by sex. It is therefore critical to understand the potential differential body composition and energy expenditure changes in response to a novel and challenging environment in both males and female bodies. Methods Data were collected from 75 healthy individuals (female = 41; ages 18-53) throughout a 3-month long expedition in the American Rockies. Body mass, body fat, and lean muscle mass were measured before, during, and after the course. Physical activity intensity and energy expenditure were also measured in a subset of participants using the wGT3X-BT Actigraph wrist monitor and an accompanying Bluetooth heart rate monitor. Results Over the 3-month period, individuals initially experienced declines in body mass, body fat percentage, and lean muscle mass. Participants partially rebounded from these deficits to maintain overall body mass with a slight recomposition of body fat and lean muscle mass. Our data also demonstrated that sex moderated total energy expenditure, where females experienced a modest decline whereas males experienced an increase in energy expenditure from the beginning to the end of the course. Conclusions Understanding changes in energy storage in the body and variation in energy expenditure between sexes during a 3-month expedition has critical implications for maintaining health and performance in an energetically demanding environment where resources may be scarce.

Little is known about human fathers' physiology near infants' births. This may represent a period during which paternal psychobiological axes are sensitive to fathers' new experiences of interacting with their newborns and that can provide insights on how individual differences in fathers' biology relate to post-partum parenting. Drawing on a sample of men in South Bend, IN (U.S.), we report results from a longitudinal study of fathers' oxytocin, cortisol, and testosterone (N = 211) responses to their first holding of their infants on the day of birth and men's reported caregiving and father-infant bonding at 2-4 months post-partum (N = 114). First-time fathers' oxytocin was higher following first holding of their newborns, compared to their pre-holding levels. Contrasting with prior results, fathers' percentage change in oxytocin did not differ based on skin-to-skin or standard holding. Drawing on psychobiological frameworks, we modeled the interactions for oxytocin reactivity with testosterone and cortisol reactivity, respectively, in predicting father-infant outcomes months later. We found significant cross-over interactions for (oxytocin × testosterone) in predicting fathers' later post-partum involvement and bonding. Specifically, we found that fathers whose testosterone declined during holding reported greater post-partum play if their oxytocin increased, compared to fathers who experienced increases in both hormones. We also observed a similar non-significant interaction for (oxytocin × cortisol) in predicting fathers' post-partum play. Fathers whose testosterone declined during holding also reported less involvement in direct caregiving and lower father-infant bonding if their oxytocin decreased but greater direct care and bonding if their testosterone increased and oxytocin decreased. The results inform our understanding of the developmental time course of men's physiological responsiveness to father-infant interaction and its relevance to later fathering behavior and family relationships.

Testosterone and oxytocin are psychobiological mechanisms that interrelate with relationship quality between parents and the quantity and quality of parenting behaviors, thereby affecting child outcomes. Their joint production based on family dynamics has rarely been tested, particularly cross-culturally.We explored family function and salivary testosterone and oxytocin in mothers and fathers in a small-scale, fishing-farming society in Republic of the Congo. Fathers ranked one another in three domains of family life pertaining to the local cultural model of fatherhood.Fathers who were viewed as better providers had relatively lower oxytocin and higher testosterone than men seen as poorer providers, who had lower testosterone and higher oxytocin. Fathers also had higher testosterone and lower oxytocin in marriages with more conflict, while those who had less marital conflict had reduced testosterone and higher oxytocin. In contrast, mothers in conflicted marriages showed the opposite profiles of relatively lower testosterone and higher oxytocin. Mothers had higher oxytocin and lower testosterone if fathers were uninvolved as direct caregivers, while mothers showed an opposing pattern for the two hormones if fathers were seen as involved with direct care.These results shed new light on parents' dual oxytocin and testosterone profiles in a small-scale society setting and highlight the flexibility of human parental psychobiology when fathers' roles and functions within families differ across cultures.La testostérone et l'ocytocine sont des mécanismes psychobiologiques qui sont interdépendants de la qualité de la relation entre les parents, ainsi que de la quantité et la qualité des comportements parentaux, et ainsi affectent les résultats de l'enfant. Leur production conjointe basée sur les dynamiques familiales a rarement été testée, en particulier de manière transculturelle. MÉTHODEIS: Nous avons investigué la fonction familiale, la testostérone et l'ocytocine chez les mères et les pères d'une micro société de pêcheurs-agriculteurs en République du Congo. Les pères se sont eux-mêmes classés dans trois domaines de la vie familiale relatif au modèle culturel local de la paternité. RÉSULTATIS: Les pères qui étaient considérés comme de meilleurs pourvoyeurs avaient relativement moins d'ocytocine et plus de testostérone que les hommes considérés comme des moins bons pourvoyeurs, ces derniers ayant des taux de testostérone plus bas et des taux d'ocytocine plus haut. Les pères présentaient également des taux plus élevés de testostérones et plus bas d'ocytocine dans les mariages plus conflictuels, alors que ceux engagés dans des mariages moins conflictuels présentaient une testostérone réduite et une ocytocine plus élevée. En revanche, les mères dans les mariages en conflit ont montré les profils opposés de testostérone relativement faible et d'ocytocine plus élevée. Les mères avaient des taux d'ocytocine et de testostérone plus élevés si les pères n'étaient pas impliqués directement dans les soins, tandis que les mères présentaient un schéma opposé pour les deux hormones si les pères étaient considérés comme impliqués dans les soins directs.Ces résultats ont jeté un nouvel éclairage sur les profils doubles de l'ocytocine et de la testostérone chez les parents, dans un nouveau contexte de micro société et ont mis en évidence la flexibilité de la psychobiologie parentale humaine lorsque les rôles et les fonctions des pères au sein des familles varient d'une culture à l'autre.

OBJECTIVES Social support positively affects health through pathways such as shaping intrapersonal emotional and psychological well-being. Lower testosterone often interrelates with psychological and behavioral orientations that are beneficial to participation in emotionally supportive relationships. Yet, little research has considered the ways in which testosterone may contribute to health outcomes related to emotional support. METHODS We draw on testosterone, social support data, and cardiovascular disease (CVD)-relevant indicators (inflammatory markers; blood pressure [BP]) from older men (n = 366) enrolled in the National Health and Nutrition Examination Survey, a US nationally representative study. We test whether men's testosterone moderates associations between emotional social support and markers related to CVD risk. RESULTS For men with relatively lower testosterone, higher levels of social support predicted lower white blood cell (WBC) counts, consistent with reduced inflammation. In contrast, men with higher testosterone exhibited elevated WBC counts with greater support. In a diverging pattern, men with lower testosterone had higher systolic and diastolic BP with higher support, whereas the slopes for systolic and diastolic BP, respectively, were comparatively flatter for men with higher levels of testosterone. CONCLUSIONS We suggest that our findings are theoretically consistent with the idea that testosterone helps shape intrapersonal and interpersonal experiences and perceptions of men's emotional support networks, thereby affecting the health implications of that support. The somewhat divergent results for WBC count vs BP highlight the need for inclusion of other neuroendocrine markers alongside testosterone as well as refined measures of perceived and received support.

Human paternal behavior is multidimensional, and extant research has yet to delineate how hormone patterns may be related to different dimensions of fathering. Further, although studies vary in their measurement of hormones (i.e., basal or reactivity), it remains unclear whether basal and/or reactivity measures are predictive of different aspects of men's parenting. We examined whether men's testosterone and cortisol predicted fathers' involvement in childcare and play with infants and whether fathers' testosterone and cortisol changed during fathers' first interaction with their newborn. Participants were 298 fathers whose partners gave birth in a UNICEF-designated “baby-friendly” hospital, which encourages fathers to hold their newborns 1 h after birth, after mothers engage in skin-to-skin holding. Salivary testosterone and cortisol were measured before and after fathers' first holding of their newborns. Basal and short-term changes in cortisol and testosterone were analyzed. Fathers were contacted 2–4 months following discharge to complete questionnaires about childcare involvement. Fathers' cortisol decreased during the time they held their newborns on the birthing unit. Fathers' basal testosterone in the immediate postnatal period predicted their greater involvement in childcare. Both basal and reactivity cortisol predicted fathers' greater involvement in childcare and play. Results suggest that reduced basal testosterone is linked with enhanced paternal indirect and direct parenting effort months later, and that higher basal cortisol and increases in cortisol in response to newborn interaction are predictive of greater paternal involvement in childcare and play, also months later. Findings are discussed in the context of predominating theoretical models on parental neuroendocrinology.

OBJECTIVES This study explores the acute endocrine reactivity of testosterone and cortisol in women engaging in everyday physical activity in a high altitude environment. METHODS Data were collected from 35 women living in the Himalayas, with women recruited from both high (>10 000 ft.) and low altitude villages (