Free leptin index and thyroid function in male highly trained athletes

Eur J Endocrinol. 2009 Dec;161(6):871-6. doi: 10.1530/EJE-09-0569. Epub 2009 Sep 22.

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 power-sprint athletes (n=13) or marathon runners (n=14). 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 (0.025+/-0.014 vs 0.085+/-0.049; 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Athletes*
  • Energy Metabolism
  • Humans
  • Leptin / blood*
  • Male
  • Receptors, Leptin / blood*
  • Running
  • Thyroid Function Tests
  • Thyroid Gland / physiology*
  • Thyrotropin / blood
  • Thyroxine / blood
  • Triiodothyronine / blood

Substances

  • Leptin
  • Receptors, Leptin
  • Triiodothyronine
  • Thyrotropin
  • Thyroxine