A Life Course Approach to the Relationship Between Fetal Growth and Hypothalamic-Pituitary-Adrenal Axis Function

Prenatal cortisol exposure impairs adrenal function but not glucose metabolism in adult sheep

Adverse environmental conditions before birth are known to programme adult metabolic and endocrine phenotypes in several species. However, whether increments in fetal cortisol concentrations of the magnitude commonly seen in these conditions can cause developmental programming remains unknown. Thus, this study investigated the outcome of physiological increases in fetal cortisol concentrations on glucose-insulin dynamics and pituitary-adrenal function in adult sheep. Compared with saline treatment, intravenous fetal cortisol infusion for 5 days in late gestation did not affect birthweight but increased lamb body weight at 1-2 weeks after birth. Adult glucose dynamics, insulin sensitivity and insulin secretion were unaffected by prenatal cortisol overexposure, assessed by glucose tolerance tests, hyperinsulinaemic-euglycaemic clamps and acute insulin administration. In contrast, prenatal cortisol infusion induced adrenal hypo-responsiveness in adulthood with significantly reduced cortisol responses to insulin-induced hypoglycaemia and exogenous adrenocorticotropic hormone (ACTH) administration relative to saline treatment. The area of adrenal cortex expressed as a percentage of the total cross-sectional area of the adult adrenal gland was also lower after prenatal cortisol than saline infusion. In adulthood, basal circulating ACTH but not cortisol concentrations were significantly higher in the cortisol than saline-treated group. The results show that cortisol overexposure before birth programmes pituitary-adrenal development with consequences for adult stress responses. Physiological variations in cortisol concentrations before birth may, therefore, have an important role in determining adult phenotypical diversity and adaptability to environmental challenges.

Defining the role of the hypothalamic-pituitary-adrenal axis in the relationship between fetal growth and adult cardiometabolic outcomes

Animal and human data demonstrate independent relationships between fetal growth, hypothalamic-pituitary-adrenal axis function (HPA-A) and adult cardiometabolic outcomes. While the association between fetal growth and adult cardiometabolic outcomes is well-established, the role of the HPA-A in these relationships is unclear. This study aims to determine whether HPA-A function mediates or moderates this relationship. Approximately 2900 pregnant women were recruited between 1989-1991 in the Raine Study. Detailed anthropometric data was collected at birth (per cent optimal birthweight [POBW]). The Trier Social Stress Test was administered to the offspring (Generation 2; Gen2) at 18 years; HPA-A responses were determined (reactive responders [RR], anticipatory responders [AR] and non-responders [NR]). Cardiometabolic parameters (BMI, systolic BP [sBP] and LDL cholesterol) were measured at 20 years. Regression modelling demonstrated linear associations between POBW and BMI and sBP; quadratic associations were observed for LDL cholesterol. For every 10% increase in POBW, there was a 0.54 unit increase in BMI (standard error [SE] 0.15) and a 0.65 unit decrease in sBP (SE 0.34). The interaction between participant's fetal growth and HPA-A phenotype was strongest for sBP in young adulthood. Interactions for BMI and LDL-C were non-significant. Decomposition of the total effect revealed no causal evidence of mediation or moderation.