Colleen Nyberg

Diurnal cortisol rhythms and child growth: Exploring the life history consequences of HPA activation among the Tsimane'

Although psychosocial stress has also been implicated as a contributor to growth failure by imposing energetic constraints during development, the direct physiological pathways by which these life history trade‐offs are imposed are not well understood. This study explores associations between diurnal cortisol rhythms and differential patterns of linear child growth among the Tsimane, a horticulturalist and foraging society in the Bolivian Amazon.

Navigating Transitions in Hypothalamic–Pituitary–Adrenal Function from Pregnancy Through Lactation: Implications for Maternal Health and Infant Brain Development

Despite the tremendous interest in understanding the effects of prenatal stress on fetal health and the programming of adult disease risk, the adaptive functions of hypothalamic–pituitary–adrenal (HPA) axis activity in healthy pregnancies and during lactation have been less widely considered. Existing research has addressed the influence of glucocorticoids on altered patterns of fetal growth and development in humans (Kuzawa and Sweet 2009; Seckl and Holmes 2007; Sloboda et al. 2005; 2009a, b) and the effects of prenatal stress in animal models, particularly with respect to offspring birth weight and stress reactivity (Drake et al. 2005; Neumann 2001; Seckl and Meaney 2004). With several important exceptions, the majority of this research has invoked the concept of “maternal stress” to encapsulate the premise that maternal activation of the HPA axis is associated with adverse birth outcomes, without the simultaneous acknowledgment that progressive elevation of the maternal HPA activity across the course of pregnancy is part of an anthropoid-typical pattern of neuroendocrine activity (Bowman et al. 2001; Smith et al. 1999). Even less is known about the HPA dynamics of pregnancy in non-Western populations with distinct infectious disease ecologies and marginal energetic status (Nyberg 2012). Given the human reproductive strategy of giving birth to secondarily altricial infants (Martin 2007), basal glucocorticoids may play a pivotal role in facilitating parturition and accelerating fetal tissue maturation in coordination with the timing of birth (Power and Schulkin 2006; Pike 2005; Smith et al. 2001). These constraints on the duration of gestation may be imposed, in part, by the metabolic demands of pregnancy (Ellison 2001, 2003; Martin 1996) and are further impacted by the obstetrical dilemma, imposed by the “tight fit” between fetal head circumference and the maternal pelvis that occurred as a result our hominin transition to obligate bipedalism (Rosenberg 2001; Rosenberg and Trevathan 1996). As a result, human birth is physiologically stressful, even by primate standards (Leigh 2004; Martin 1996; Rosenberg 2001; Rosenberg and Trevathan 1996).