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THOMAS W. BOYDEN, RICHARD W. PAMENTER, PHILIP STANFORTH, THOMAS ROTKIS, JACK H. WILMORE, Evidence for Mild Thyroidal Impairment in Women Undergoing Endurance Training, The Journal of Clinical Endocrinology & Metabolism, Volume 54, Issue 1, 1 January 1982, Pages 53–56, https://doi.org/10.1210/jcem-54-1-53
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Abstract
The effects of endurance training on body composition and the pituitary-thyroid axis were studied in 29 healthy, young (mean age, 28.7 yr), regularly menstruating women. Women who were initially jogging a mean of 13.5 miles/l week were selected for this study to minimize dropouts. Body composition, measured by hydrostatic weighing, and nonfasting plasma concentrations of T4, T3, rT3, TSH, and TRH-stimulated TSH, measured by RIA, were examined initially and after each subject's weekly mileage had increased to 30 miles (Δ30) for at least 2 consecutive weeks.Two subjects were found to have compensated primary hypothyroidism and were not included in the subsequent data analysis. At Δ30, mean total body weight did not change, mean fat weight decreased (−1.02 kg; P <0.005), and mean lean weight increased (+0.75 kg; P < 0.05). T4 and unstimulated TSH did not change. However, mean (±SE) T3decreased from 107.2 ± 4.4 to 97.9 ± 3.4 ng/dl (P <0.025), and mean rT3 decreased from 170.9 ± 13.9 to 154.6 ± 13.2 pg/ml (P < 0.025). The decreases in T3 and rT3 were accompanied by significantly greater TSH responses to TRH stimulation [mean (±SE) area under TSH curve, 1381.4 ± 123 vs. 1712.8 ± 202 μIU/ml min; P < 0.01]. These results indicate that physically active women who undergo additional endurance training 1) become more lean without a change in total body weight, and 2) have changes in T3, rT3; and TRH-stimulated TSH indicative of mild thyroidal impairment.(J Clin Endocrinol Metab53: 53, 1982)
