Investigations of thyroid hormones and antibodies in obesity: leptin levels are associated with thyroid autoimmunity independent of bioanthropometric, hormonal, and weight-related determinants.
OBJECTIVE
Obesity can alter the thyroid hormone status as a result of a dysregulated endocrine loop between the hypothalamo-pituitary unit and adipose tissue. The adipocytokine leptin has been shown to promote autoimmunity; hence, we aimed to clarify whether leptin excess of obesity could increase the susceptibility to develop autoimmune thyroid disease (AITD).


METHODS
This cross-sectional study was performed in a tertiary care center.


METHODS
Free thyroid hormones, TSH, thyroglobulin, and antithyroid antibodies levels were tested in 165 obese and 118 lean subjects. Results were plotted against variables related to body composition, leptin levels, glucose homeostasis, energy expenditure, and pattern of weight accrual.


RESULTS
Compared with controls, obese patients had lower free T3 levels and free T4 levels (P<0.01), greater prevalence of hypothyroidism (P<0.05), and higher commonness of antithyroid antibodies (P<0.05). As a marker of AITD, thyroid peroxidase antibodies were more frequent in the obese group (P<0.01). Correlation analysis showed that leptin levels were associated with AITD (P<0.01) independent of bioanthropometric variables. Multiple logistic regression analysis in pooled groups identified female sex and leptin as significant predictors of AITD.


CONCLUSIONS
Obesity increases the susceptibility to harbor AITD with an emerging role for leptin as a peripheral determinant, which needs to be confirmed in future investigations.
Department of Clinical and Molecular Medicine, Università del Piemonte Orientale A. Avogadro, Novara, Italy. paolo.marzullo@med.unipmn.it
Paolo
P
Marzullo
Alessandro
A
Minocci
Maria Antonella
MA
Tagliaferri
Gabriele
G
Guzzaloni
Annamaria
A
Di Blasio
Clotilde
C
De Medici
Gianluca
G
Aimaretti
Antonio
A
Liuzzi
D000328:Adult; D000704:Analysis of Variance; D001323:Autoantibodies / Q000276:immunology*; D015551:Autoimmunity / Q000276:immunology*; D001823:Body Composition / Q000276:immunology; D015992:Body Mass Index; D001835:Body Weight; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000276:immunology; D007333:Insulin Resistance / Q000276:immunology; D020738:Leptin / Q000097:blood* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood* / Q000276:immunology; D018579:Patient Selection; D012737:Sex Factors; D013961:Thyroid Gland / Q000276:immunology*; D013974:Thyroxine / Q000097:blood* / Q000276:immunology; D014284:Triiodothyronine / Q000097:blood* / Q000276:immunology
D001323:Autoantibodies; D020738:Leptin; D014284:Triiodothyronine; D013974:Thyroxine