Serum Thyroid-Stimulating Hormone Levels and Body Mass Index Percentiles in Children with Primary Hypothyroidism on Levothyroxine Replacement

Abstract

Objective:To determine the association, if any, between thyroid-stimulating hormone (TSH) levels and body mass index (BMI) percentiles in children with primary hypothyroidism who are chemically euthyroid and on treatment with levothyroxine.Methods:This retrospective cross-sectional study consisted of a review of medical records from RUSH Medical Center and Stroger Hospital, Chicago, USA of children with primary hypothyroidism who were seen in the clinic from 2008 to 2014 and who were chemically euthyroid and on treatment with levothyroxine for at least 6 months. The patients were divided into two groups based on their TSH levels (0.34-<2.5 mIU/L and ≥2.5-5.6 mIU/L). The data were analyzed by Spearman rank correlation, linear regression, cross tabulation and chi-square, Mann-Whitney U test, and Kruskal-Wallis test.Results:One hundred and forty-six children were included, of which 26% were obese (BMI ≥95%), 21.9% overweight (BMI ≥85-<95%), and 52.1% of a healthy weight (BMI ≥5-<85%). There was a significant positive correlation between TSH and BMI percentiles (r=0.274, p=0.001) and a significant negative correlation between TSH and serum free T4 (r=-0.259, p=0.002). In the lower TSH group, 68.4% of the children had a healthy weight, while the percentage of obese children was 60.5% in the upper TSH group (p=0.012).Conclusion:In children diagnosed with primary hypothyroidism who are chemically euthyroid on treatment with levothyroxine, there is a positive association between higher TSH levels and higher BMI percentiles. However, it is difficult to establish if the higher TSH levels are a direct cause or a consequence of the obesity. Further studies are needed to establish causation beyond significant association.

Assessment of the Effect of Selenium Supplementation on Production of Selected Cytokines in Women with Hashimoto’s Thyroiditis

“…Therefore, it is possible that even small changes in thyroid function, as manifested by changes in thyroid hormone levels within the normal range, may have affected BMI through small, but long-term, changes in the body's energy metabolism, consistent with the assumption made by Knudsen et al [72]. In addition, a positive correlation between TSH I and BMI was noted (Table 2), which is consistent with the results of other studies conducted among people without thyroid dysfunction [73][74][75][76], as well as studies involving children with primary hypothyroidism treated for at least 6 months with L-T 4 to restore euthyroidism [77]. Siemi ńska et al also noted a dependence between TSH and BMI among postmenopausal women both with properly functioning thyroid and subclinical hypothyroidism (there were cases in that study with anti-TPO antibodies present) [78].…”

Thyroid hormone levels and BMI-SDS changes in adolescents with obesity

“…When treated with levothyroxine, only modest weight loss can be seen and this is mediated primarily by loss of excess water and salt rather than fat ( 22 ). In children with primary hypothyroidism who are euthyroid on treatment with levothyroxine, a positive association between TSH levels and BMI percentiles was shown ( 23 ). On the other hand, hyperthyroidism is traditionally linked to weight loss or even underweight.…”

Levothyroxine in Children

“…These data suggest there is no place for LT4 in the general management of obesity in children with TSH levels consistent with subclinical hypothyroidism. Correlations of higher TSH levels with higher BMI in hypothyroid children controlled on LT4 have been observed [68], but this association is probably not independently causative for obesity [1,69].…”