Free leptin index and thyroid function in male highly trained athletes.
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.


CONCLUSIONS
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.
Perseghin
Gianluca
G
Department of Sport, Nutrition and Health, Università degli Studi di Milano, via Kramer 4/a 20129 Milan, Italy. perseghin.gianluca@hsr.it
Lattuada
Guido
G
Ragogna
Francesca
F
Alberti
Giampietro
G
La Torre
Antonio
A
Luzi
Livio
L
D000293:Adolescent; D000328:Adult; D056352:Athletes; D004734:Energy Metabolism; D006801:Humans; D020738:Leptin / Q000097:blood*; D008297:Male; D054411:Receptors, Leptin / Q000097:blood*; D012420:Running; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000502:physiology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D020738:Leptin; D054411:Receptors, Leptin; D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine