Body adiposity, leptin and serum throtropin association in euthyroid premenopausal women
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Date
2017-11
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The present cross-sectional, population-based study was conducted among euthyroid premenopausal women (mean age 25.7 ± 3.2 years, mean BMI 24.87 ± 3.3 kg/m2) to investigate the association of degree of obesity and serum leptin with the serum thyrotropin concentration. Eighty-one healthy euthyroid premenopausal women, (26 normal and 55 overweight and obese subjects, as per BMI) with no known selfreported history of thyroid dysfunction, were studied. The mean energy intake of the study population was 83.5% of the RDA and the mean PAL revealed that majority of the study respondents perform sedentary activity. Notably, a considerable number of subjects showed high mean values of body fat percent i.e. ≥30% (61.7%) indicating generalized obesity and waist circumference at ≥73.50 cm (71.6%) indicating abdominal obesity. The study population also exhibited a high prevalence of subcutaneous adiposity (59.3%) and intra-abdominal (40.7%) adiposity. Out of the various anthropometric indices used to determine obesity in the study population with body fat percent as ‘standard’, BMI and WHtR displayed high sensitivity and lower misclassification rate at the optimal cutoff points of ≥23.1 kg/m2 (Sens. 98%, Spec. 80.6%) and ≥0.47 (Sens. 94%, Spec. 90.4%), respectively in the ROC curve analysis. Uncomplicated euthyroid overweight and obese premenopausal women showed increased (p<0.001) serum leptin (37.31±12.4 vs 10.39±4.9 ng/ml) and moderately elevated TSH levels (3.45±1.1 vs 0.90±0.4 mIU/L) than normal subjects. Evidently, a substantial number of subjects who were obese displayed TSH distribution in the third [2.44-4.05 mIU/L (46.3%)] and fourth quartile [4.06-5.40 mIU/L (43.9%)]. The proportion of subjects with TSH distribution in upper quartiles significantly (p<0.001) increased with increasing quartiles of leptin and with the increase in abdominal, subcutaneous and intra-abdominal adiposity. The relationship of dietary intake and physical activity status of the study population was also assessed with TSH. TSH correlated significantly and positively with leptin (r=0.66); body weight (r=0.45); BMI (r=0.67); body fat percent (r=0.73); subcutaneous adipose tissue (r=0.60); intra-abdominal adipose tissue (r=0.53); waist circumference (r=0.59); hip circumference (r=0.42); neck circumference (r=0.28); BMR (r= 0.25) and negatively with physical activity level (r= -0.34) in overweight and obese euthyroid subjects. In a multivariable regression analysis, BMI (β=0.84), body fat percent (β=0.52), total abdominal fat (β=0.72) and leptin (β=0.31) associated significantly with serum TSH after adjusting for various variables. Considering the clinical evidence provided by this observational study, it may possibly be implied that a direct relationship exists between grades of obesity and TSH and that leptin might be the possible link between thyroid function and adiposity which may stimulate the rise in TSH directly or indirectly to regulate the thermogenesis in obesity.
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