Positive adaptation of HPA axis function in women during 44 weeks of infantry-based military training.

BACKGROUND: Basic military training (BMT) is a useful model of prolonged exposure to multiple stressors. 8-12 week BMT is associated with perturbations in the hypothalamic-pituitary-adrenal (HPA) axis which could predispose recruits to injury and psychological strain. However, characterisations of HPA axis adaptations during BMT have not been comprehensive and most studies included few if any women. METHODS: We studied women undertaking an arduous, 44-week BMT programme in the UK. Anxiety, depression and resilience questionnaires, average hair cortisol concentration (HCC), morning and evening saliva cortisol and morning plasma cortisol were assessed at regular intervals throughout. A 1-h dynamic cortisol response to 1 µg adrenocorticotrophic hormone-1-24 was performed during weeks 1 and 29. RESULTS: Fifty-three women (aged 24 ± 2.5 years) completed the study. Questionnaires demonstrated increased depression and reduced resilience during training (F 6.93 and F 7.24, respectively, both p < 0.001). HCC increased from 3 months before training to the final 3 months of training (median (IQR) 9.63 (5.38, 16.26) versus 11.56 (6.2, 22.45) pg/mg, p = 0.003). Morning saliva cortisol increased during the first 7 weeks of training (0.44 ± 0.23 versus 0.59 ± 0.24 µg/dl p < 0.001) and decreased thereafter, with no difference between the first and final weeks (0.44 ± 0.23 versus 0.38 ± 0.21 µg/dl, p = 0.2). Evening saliva cortisol did not change. Fasting cortisol decreased during training (beginning, mid and end-training concentrations: 701 ± 134, 671 ± 158 and 561 ± 177 nmol/l, respectively, p < 0.001). Afternoon basal cortisol increased during training while there was a trend towards increased peak stimulated cortisol (177 ± 92 versus 259 ± 13 nmol/l, p = 0.003, and 589 ± 164 versus 656 ± 135, p = 0.058, respectively). DISCUSSION: These results suggest a normal stress response in early training was followed quickly by habituation, despite psychological and physical stress evidenced by questionnaire scores and HCC, respectively. There was no evidence of HPA axis maladaptation. These observations are reassuring for women undertaking arduous employment.

Circulatory and metabolic effects of alpha-adrenergic blockade in the hyperinsulinemic ovine fetus.

OBJECTIVES: Fetuses of diabetic women exhibit hypoxemia, elevated catecholamine concentrations at birth, and increased incidence of death. Our previous findings suggested that experimental fetal hyperinsulinemia results in a surge in catecholamines with cardiovascular changes supported by increased beta-adrenergic activity. The present experiments were designed to assess the contribution of alpha-adrenergic stimulation to the hemodynamic changes in the hyperinsulinemic ovine fetus. METHODS: Combined ventricular output, regional organ blood flow, vascular resistance, metabolism, and catecholamine concentrations were measured before and during an infusion of insulin and during continued infusion with alpha-adrenergic blockade (phentolamine) in eight chronically catheterized fetal sheep. RESULTS: Fetal insulin infusion produced hyperinsulinemic-hypoglycemia, a surge in epinephrine and norepinephrine concentration, and increases in the combined ventricular output (blood flow to the fetus plus placenta) and regional blood flow to the fetus, heart, stomach, gastrointestinal tract, fat, and carcass. In the hyperinsulinemic state, alpha-adrenergic blockade was associated with additional increases in fetal norepinephrine concentration and no major changes in combined ventricular output or blood flow to the body of the fetus, except for decreased blood flow to the stomach and lungs, and a decrease in stroke volume. CONCLUSIONS: Because vasodilation characterizes the hyperinsulinemic state, alpha-adrenergic stimulation contributes less to compensatory cardiovascular changes in the hyperinsulinemic fetus than that which we previously have shown for beta-adrenergic stimulation.