Effects of Suckling on Hypothalamic-Pituitary-Adrenal Axis Responses to Psychosocial Stress in Postpartum Lactating Women

Abstract

In several studies lactation has been shown to be associated with a hypothalamic-pituitary-adrenal axis hyporesponsiveness to physical and psychological stressors. As it is not known whether the marked blunting of endocrine stress reactivity in women can be ascribed to suckling as a short-term effect or to lactation in general, the acute effects of suckling on the hypothalamic-pituitary-adrenal axis and the sympathetic-adrenal-medullary system responses to mental stress were investigated in lactating women.Forty-three lactating women were randomly assigned either to breast-feed or to hold their infants for a 15-min period with the onset 30 min before they were exposed to a brief psychosocial stressor (Trier Social Stress Test). Both breastfeeding and holding the infant yielded significant decreases in ACTH, total plasma cortisol, and salivary free cortisol (all P < 0.01). There were no significant differences in baseline hormone levels between the groups 1 min before the stress test. In response to stress exposure, ACTH, total plasma cortisol, salivary free cortisol, norepinephrine, and epinephrine were significantly increased in all lactating women (all P < 0.001). However, total cortisol and free cortisol responses to stress were attenuated in breast-feeding women (P ‫؍‬ 0.001 and P ‫؍‬ 0.067, respectively), who also showed significantly decreasing PRL levels during the stress test (P ‫؍‬ 0.005). In addition, there was no change in plasma oxytocin or vasopressin in response to the stressor. Breast-feeding as well as holding led to decreased anxiety (P < 0.05), whereas, in contrast, stress exposure worsened mood, calmness, and anxiety in the total group (all P < 0.001).From these data we conclude that lactation in women, in contrast to that in rats, does not result in a general restraint of the hypothalamic-pituitary-adrenal axis response to a psychosocial stressor. Rather, suckling is suggested to exert a short-term suppression of the cortisol response to mental stress. (J Clin Endocrinol Metab 86: 4798 -4804, 2001) E VIDENCE FROM ANIMAL and human studies has suggested that suckling is associated with significant alterations in the reactivity of the hypothalamic-pituitaryadrenal (HPA) axis during the postpartum period (1, 2). Observations in the lactating rat have shown an endocrine hyporesponsiveness to physical and psychological stressors, including attenuated secretion of ACTH (3-7), corticosterone (3-5, 8 -11), catecholamines (12), oxytocin (9, 13-15), and PRL (12, 16).In humans, the effect of lactation on stress-responsive neurohormonal systems has been explored, to date, only for treadmill exercise. Altemus and associates (17) found significantly attenuated plasma ACTH, cortisol, and glucose responses to physical stress in lactating compared with nonlactating women. However, the effects of suckling on endocrine as well as behavioral responses to a psychosocial stress paradigm in humans have not yet been investigated. More important, it is not known whether the marked blunting of endocrine stress responsi...

Lactation and appetite-regulating hormones: increased maternal plasma peptide YY concentrations 3–6 months postpartum

“…Despite the well-known reduced hypothalamic-pituitary-adrenal axis activity in response to stressors, as well as changes in the profile of prolactin and oxytocin concentrations during breast-feeding, we did not find any relevant difference in gut-derived appetite-regulating hormones during one single breast-feeding episode (30) . Limitations of this study are the lack of data on maternal education, employment, income, feeding patterns and weight changes over time, as all these parameters could affect the metabolic profile.…”

Resilience and mental health

“…Suckling-related factors, which activate the brain oxytocin and prolactin systems, have also been found to be associated with a positive mood state (Heinrichs et al 2001). However, a label of all these behavioural or neuronal factors as potential resilience is a relative (i.e., context-dependent), but not an absolute category.…”

Oxytocin pathways in the intergenerational transmission of maternal early life stress

“…In a recent meta-analysis, OT was shown to not attenuate HPA axis reactivity after stress induction per se but does so after laboratory stress protocols that robustly activate the HPA axis (Cardoso et al, 2014). In healthy postpartum women, breastfeeding, which often serves as a proxy for OT activity, was associated with lower cortisol secretion after a psychosocial stressor (Heinrichs et al, 2001). Interestingly, at 2 months postpartum, mothers with high depression scores had lower peripheral OT concentrations during breastfeeding (Stuebe et al, 2013).…”