Free leptin index and thyroid function in male highly trained athletes

Abstract

Objective: Exercise training may cause changes in thyroid function. This thyroid response may be due to exercise-induced modulation of energy metabolism but also of the adipocytes endocrine function. In particular, the role of leptin and of circulating soluble leptin receptor (sOB-R) was unexplored. The aim of this study was to assess the relationships between thyroid function, whole body energy metabolism, and adipokines -mainly leptin and its receptor, sOB-R. Methods: We measured serum TSH, free tri-iodothyronine (FT 3 ), free thyroxine, leptin, and sOB-R and assessed energy homeostasis by means of indirect calorimetry, in 27 highly trained athletes and 27 sedentary, healthy men. Results: TSH-FT 3 ratio was lower in athletes (P!0.03), either in sustained power or anaerobic powersprint athletes (nZ13) or marathon runners (nZ14). Whole body respiratory quotient was lower in athletes. Fasting serum sOB-R was higher and leptin lower in athletes than controls. Also serum adiponectin, resistin, and retinol binding protein-4 concentrations were different in athletes than in controls. The ratio between leptin and sOB-R, the free leptin index (FLI), was lower in athletes than in controls (0.025G0.014 vs 0.085G0.049; P!0.001). In multivariate analysis, FLI retained independent association with TSH-FT 3 ratio. Conclusion: Male, elite athletes had lower TSH-FT 3 ratio and FLI than controls while FLI was independently associated with TSH-FT 3 ratio supporting the hypothesis that the level of biologically active leptin is involved in the adaptive response of thyroid function in professional athletes.

Combined effects of androgen anabolic steroids and physical activity on the hypothalamic–pituitary–gonadal axis

“…Some authors reported no exercise induced effects on serum 435 TSH in trained athletes and sedentary individuals [42,43] whereas 436 other suggested a basal [41], or acute decrease of TSH concentra-437 tion after long term exercise [44,45] and resistance training [46] 438 similar to our results (Fig. 6B).…”

“…38 Satellite cells are the basis for skeletal muscle recovery and 39 regeneration following injury caused by trauma or unfamiliar 40 exercise. In a rat model Schmalenbruch and Lewis could 41 demonstrate that unloaded adult muscle has a relatively slow 42 nuclei turnover of 1-2% compared to young muscle [9]. This is 43 known to change dramatically in response to injury.…”

Associations of Aerobic and Strength Exercise with Clinical Laboratory Test Values

“…Thyroid hormones play an important role in metabolism, growth, tissue differentiation, fatty acid oxidation, and thermoregulation in response to exercise training [51][52][53]. Previous studies evaluating thyroid function in athletes have shown contradicting results [54,55]. In elite soccer players, TSH levels have been shown to increase over a competitive season [54].…”

Physiological changes of Exercise of Thermogenesis, Thyroid Homeostasis and Inflammations

“…Some authors reported no major effect of exercise training on serum TSH levels in professional athletes and sedentary individuals suggesting that the influence of chronic exercise is likely to be small; in contrast other authors suggested long-term exercise training may lead to downregulation of thyroid hormone concentrations. Among the candidate factors, this response may be induced by the exercise induced negative energy balance as well as signaling alterations in the hypothalamus-pituitary-thyroid and hypothalamusadipocyte-leptin axes [5].…”