Undiagnosed thyroid dysfunction, leptin and body mass index

I Olaizola; M L Granada; M T Julian; C Castell; A Serra; A Alastrue; A Lucas

P319

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Endocrine Abstracts (2011) 26 P319

ECE2011 Poster Presentations Obesity (47 abstracts)

Undiagnosed thyroid dysfunction, leptin and body mass index

I Olaizola ^1, , M L Granada ^3, , M T Julián ^1, , C Castell ⁷ , A Serra ^2, , A Alastrué ^4, & A Lucas ^1,

Err

Author affiliations

¹Endocrinology and Nutrition Service. Germans Trias i Pujol, Hospital, Badalona, Barcelona, Spain; ²Department of Medicine. Autonomous University of Barcelona, Badalona, Barcelona, Spain; ³Biochemistry Service. Germans Trias i Pujol, Hospital, Badalona, Barcelona, Spain; ⁴Autonomous University of Barcelona, Badalona, Barcelona, Spain; ⁵Nephrology Service. Germans Trias i Pujol, Hospital, Badalona, Barcelona, Spain; ⁶General and Digestive Surgery Service. Germans Trias i Pujol. Hospital, Badalona, Barcelona, Spain; ⁷General Direction of Public Health. Health Deparment. Generalitat of Catalonia, Barcelona, Spain.

Introduction: Leptin seems to be a major link between obesity and thyroid dysfunction.

Design: To analyze the relationship between thyrotropin (TSH) and leptin (LP) plasma concentrations and body mass index (BMI), in 785 subjects (448 women) of 41.27±9.72 years and BMI 28.91±9.8 (18.04–93.98 kg/m²), without diagnosed thyroid disease or pregnancy, concentrations of TSH, free thyroxine (FT₄), LP, glycemia and insulinemia were determined and HOMA index, calculated. The group of subjects was divided into three subgroups according to BMI: 18–30 (n=594, 1), 30–40 (n=97, 2) and >40 kg/m² (patients with morbid obesity, n=94, 3). The statistical analysis was performed with the SPSS package using the logarithm of the variables without normal distribution.

Results: The undiagnosed hypothyroidism (TSH >4 mU/l) was 2.4, 4.1 and 9.9% for subgroups 1, 2 and 3 respectively (P=0.002, 0.002). In the global group, the TSH correlated directly and significantly with BMI and the HOMA and inversely, with FT₄ (P=0.007, 0.04, 0.006). In men, TSH only correlated directly and significantly with LP (P=0.01) and in women, directly, with BMI, LP and the HOMA (P=0.015, 0.001, 0.014) and inversely with FT₄ (P=0.001). The multivariate analysis performed with TSH as the dependent variable showed that in men, the LP was the only predictor of the TSH concentration variations (P=0.049) while, in women, BMI and FT₄ were the predictors of these variations (P=0.023; <0.000).

Conclusions: Undiagnosed hypothyroidism is more prevalent in patients with obesity and even more in those with morbid obesity than in the non obese population.

The predictor factors of TSH concentration variations are different in men and women.