Thyroid hormone responses during an 8-hour period following aerobic and anaerobic exercise.

The purpose of this study was to compare the daytime hourly responses of total thyroxine (T4) and triiodothyronine (T3) during an 8-hour recovery period following aerobic and anaerobic exercise to an equivalent non-exercise, control period. The data were examined for hourly mean differences as well as by determination of the integrated area under the curve (AUC) responses. Significant persistent elevations (hourly concentrations and AUC) from control levels in total T4 following both aerobic and anaerobic exercise were found. Total T3, however, was transiently elevated (only in the hourly concentration immediately following exercise) compared with the control following aerobic exercise, but remained unaffected by anaerobic exercise. No significant changes in the total T3 AUC responses were found due to exercise. The present findings demonstrate that exercise, aerobic and anaerobic, disrupts the daytime hourly pattern for total T4 in the blood, but apparently has minimal effect on total T3.