The activity of hypothalamicpituitary axis is increased in obese patients and some hormonal changes can be observed as a consequence. Although the effects of hypothyroidism or hyperthyroidism on weight are clearly demonstrated data regarding the effects of relatively minor defects is limited. There are different results in the literature concerning thyroid function status in obesity, some indicating no change, others elevated serum thyroid stimulating hormone (TSH), free triiodothyronine (fT3) and free thyroxine (fT4) levels and some others TSH in the upper normal range as well as fT4 in the lower normal. Considering the increasing prevalence of obesity and its association with higher rates of morbidity and mortality, the relation between thyroid functions and body mass becomes more important. In the present study, the relation between body mass index (BMI) and alterations in thyroid functions within normal ranges was aimed to be investigated in obese patients. Three hundred and 57 euthyroid obese patients (309 females, 48 males, mean age: 42 years) were included in the study. Thyroid functions, BMI and epidemiological characteristics of the patients were retrospectively evaluated (Table 1). The patients were divided into two groups according to a cut-off BMI value of 40 kg/m2. No statistically significant difference was detected between the groups in respect of gender, place of birth, place of residence, smoking and family history. Obese patients with BMI≥40 kg/m2 were older and showed lower serum free thyroxine level (fT4) than obese patients with BMI<40 kg/m2 (P<0,01). Our data indicated that, although thyroid functions were normal in the studied obese population, fT4 and BMI were related. Minor variations in thyroid functions may importantly influence the prevalence of obesity in a population.
25 - 29 Apr 2009
European Society of Endocrinology