Suppression of hypothalmic-pituitary-adrenal axis responses to stress in lactating women.
In the rat, lactation suppresses a variety of physiological responses to stress. We investigated whether stress-responsive neurohormonal systems are also restrained during breast feeding in humans. We chose treadmill exercise as a stressor because this stimulus produces an exercise intensity-dependent activation of the hypothalamic-pituitary-adrenal axis and the sympathomedullary system that is independent of differences in physical conditioning among subjects. Ten lactating and ten nonlactating women who were between 7 and 18 weeks postpartum performed 20 min of graded treadmill exercise. The final 5 min of exercise was set to elicit 90% of the maximal oxygen uptake of each subject. Plasma ACTH, cortisol, and glucose responses to exercise were significantly attenuated in lactating women (P < 0.001, P < 0.05, and P < 0.001, respectively). Basal norepinephrine levels were also reduced in lactating women (P < 0.05). These results indicate that stress-responsive neurohormonal systems are restrained in lactating women.
Altemus
M
M
Division of Intramural Research Programs, National Institute of Mental Health, Bethesda, Maryland 20892, USA.
Deuster
P A
PA
Galliven
E
E
Carter
C S
CS
Gold
P W
PW
D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000378:metabolism; D000328:Adult; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D004837:Epinephrine / Q000097:blood; D004958:Estradiol / Q000097:blood / Q000378:metabolism; D005080:Exercise Test; D005260:Female; D006728:Hormones / Q000097:blood / Q000378:metabolism*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology*; D007774:Lactation / Q000502:physiology*; D009638:Norepinephrine / Q000097:blood; D010121:Oxytocin / Q000097:blood / Q000378:metabolism; D010913:Pituitary-Adrenal System / Q000502:physiology*; D049590:Postpartum Period / Q000502:physiology*; D011388:Prolactin / Q000097:blood / Q000378:metabolism; D051381:Rats; D013312:Stress, Physiological; D013997:Time Factors; D014667:Vasopressins / Q000097:blood / Q000378:metabolism
D001786:Blood Glucose; D006728:Hormones; D014667:Vasopressins; D004958:Estradiol; D010121:Oxytocin; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D006854:Hydrocortisone; D009638:Norepinephrine; D004837:Epinephrine