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Publication AbstractsPituitary-Adrenal and Pituitary-Thyroid Hormone Responses During Exercise-Cold Exposure After 7 Days of Exhaustive ExerciseJohn W. Castellani, Andrew J. Young, Dean A. Stulz, David W. DeGroot, Laurie A. Blanchard, Janet E. Staab, and Michael N. SawkaAviat Space Environ Med 2002; 73:544-50 AbstractBackground: After several days of exhaustive exercise in mild-warm environments, cutaneous vasoconstrictor responses to cold exposure are less effective in conserving body heat than in the rested condition. Hypothalamic-pituitary-adrenal and hypothalamic-pituitary-thyroid axes hormones could mediate this response since they may affect vasoconstriction. The effects of exertional fatigue on pituitary-adrenal hormones and thyroid hormone responses to exercise-cold stress are unknown. Hypothesis: We hypothesized that 7 consecutive days of exercise would decrease adrenocorticotropin (ACTH) and cortisol, while elevating thyroid stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) and that these hormones would be related to a blunted vasoconstrictor response to cold. Methods: Nine male volunteers walked, completely wetted, for up to 6 h in 5°C air, when rested (day 0, control) and after 7 consecutive days (day 7) of exhaustive exercise (4 h each day of mixed aerobic and anaerobic activities in thermoneutral conditions). Blood was sampled on day 0 and day 7 at baseline (0700 hours), and before and immediately after cold exposure. Results: At 0700 hours, ACTH and cortisol were elevated (p < 0.05) after 7 d of exercise, compared with control conditions. Following exercise-cold exposure, cortisol, T3, and T4 increased (p < 0.05) similarly on both day 0 and day 7. ACTH and TSH did not increase as a result of exercise-cold exposure on either day. Conclusions: These data indicate that 7 d of exercise elevates basal (0700 hours) pituitary-adrenal stress hormones (ACTH, cortisol). However, 7 d of exercise did not modify adrenal or thyroid hormone responses, relative to the day 0 cold exposure, suggesting that they are not responsible for the blunted vasoconstriction during exercise-cold exposure following 7 consecutive days of exercise.Keywords: ACTH, cortisol, skin temperature, thyroxine, vasoconstriction. Information on subscribing, and on obtaining copies of an article or of an entire issue. Table of Contents for Volume 73, Number 6 of the ASME journal.
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