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Effect of Levo-thyroxine Treatment on Weight and BMI in Children with Acquired Hypothyroidism

« Back to Volume 24, Issue 2, November 2008 - Table of Contents

Lomenick and colleagues performed a retrospective analysis of children with the diagnosis of hypothyroidism evaluated in their clinics between July 1995 and July 2006. These authors sought to determine short-term and long-term changes in weight with levo-thyroxine treatment of hypothyroidism. Inclusion criteria were met by 68 subjects, ie under 18 years of age at the time of initial assessment, diagnosis of acquired hypothyroidism, initiation of levo-thyroxine treatment at the first clinic visit, and seen at least once in follow-up. History, physical exams, and laboratory data were obtained from the medical records. Subjects were examined for weight to the nearest 0.1 kg and height to the nearest 0.1 cm as well as BMI. Subjects were divided into 2 groups based on their weight at the second clinic visit compared to their weight at the initial visit; those who lost weight (Group 1; n=21) and those who had no change in weight or who gained weight (Group 2; n=47). Variables were assessed at baseline, first follow-up visit after starting treatment, first visit 2 years after starting treatment, and the first visit 4 years after starting treatment.

The degree of hypothyroidism was variable (TSH 5.5 – 1600 µU/mL) and 81% of the subjects were female. There were no differences in mean age, weight, height, or BMI at baseline between Groups 1 and 2. Children in Group 1 had more severe hypothyroidism with an initial mean TSH of 414 vs 41.4 in Group 2. As anticipated, mean TSH decreased (147 – 5.0 µU/mL) from the initial visit to the first follow-up (an average of 4.4 months after starting treatment). The decrease was not associated with a significant change in mean weight, mean weight percentile, weight z-score, BMI, BMI percentile, or BMI z-score. Mean weight loss in Group 1 children was 2.3 kg which was not significant from baseline.

Thirty subjects had at least 2 years of follow-up. During this interval BMI percentile did not change significantly nor did BMI z-score, weight percentile, or weight z-score. Nineteen children had 4 years of follow and again there was no significant change in BMI percentile, BMI z-score, weight percentile, or weight z-score. Thirty-nine of the 68 subjects were classified as overweight or obese initially (based on BMI). These children exhibited no change in weight or BMI from baseline to the first follow-up. At the second visit (first follow-up) significant correlations were found between initial TSH and change in weight percentile, BMI, BMI z-score, and BMI percentile. After 2 years the initial TSH was negatively correlated with BMI percentile and after 4 years there was a trend toward a correlation between initial TSH and change in BMI percentile.

The authors pointed out that the association between hypothyroidism and weight gain is well described in pediatric textbooks including textbooks on endocrinology and pediatric endocrinology. Indeed practitioners evaluating overweight children often request thyroid tests and prescribe levo-thyroxine for mild hypothyroidism in hope of assisting with weight loss. The current study does not support the notion of hypothyroidism as a cause of obesity and the authors suggested that practitioners should not expect significant changes in weight after treatment in most children with hypothyroidism.

Lomenick JP, El-Sayyid M, Smith WJ. Effect of levo-thyroxine treatment on weight and body mass index in children with acquired hypothyroidism. J Pediatr. 2008:152:96-100.

Editor’s Comment

Lomenick and colleagues have performed a very valuable study. Pediatric endocrinologists who receive referrals from primary care physicians of overweight children with slight elevations in TSH levels are well aware that treatment of such subclinical hypothyroidism rarely achieves significant weight loss. Despite the retrospective nature of this manuscript, it provides significant and important supporting evidence for discouraging unrealistic expectations in families whose overweight children have mild elevations in TSH. This manuscript should be mandatory reading for all physicians who hold out such hope to children or who make referrals to pediatric endocrinologists of such children. The pediatric endocrinology community should congratulate Lomenick and his colleagues and thank them for such a timely manuscript.

William L. Clarke, MD

« Back to Volume 24, Issue 2, November 2008 - Table of Contents

Last Updated: 2/2/2011