Thyroid Treatment No 'Quick Fix' For Weight Loss In Children

"Parents of overweight children often desire a 'quick fix' for the problem and request thyroid tests, but, unfortunately, screening for hypothyroidism is not the answer," said the study's lead author, Dr. Jefferson P. Lomenick, an assistant professor at the University of Kentucky College of Medicine Department of Pediatrics' Division of Pediatric Endocrinology. "Most experts agree thyroid function tests are generally unnecessary in an overweight child if he/she has normal linear growth and no other symptoms of hypothyroidism. The results of our study support this."

The study followed 68 children with acquired hypothyroidism treated in the pediatric endocrinology clinic at Kentucky Children's Hospital from 1995 to 2006. Most of the subjects had severe cases of hypothyroidism. Researchers found treatment with levo-thyroxine, which normalized the children's thyroid levels, did not lower weight or BMI from baseline to any time point measured, either short-term or long-term.

"These findings were true for the group as a whole, as well as those children who were overweight," Lomenick said. "In fact, the entire group of 68 subjects actually gained 2.4 pounds by the first follow up visit despite their treatment. We did find that about a third of the children experienced weight loss by the second visit. However, these subjects had extremely severe cases of hypothyroidism, far worse than the children who did not lose weight, and they didn't lose that much, only about five pounds."

Lomenick said he is not surprised by these findings. "Although this is the first study in children to address this issue, there have been a few reports in adults which show similar results."

Although hypothyroidism is commonly believed to cause weight gain, Lomenick said the disease has been given a bad reputation.

"Long-standing hypothyroidism causes accumulation of a proteinaceous fluid in the subcutaneous tissues called myxedema," said Lomenick. "The amount of adipose, or fatty tissue, is not really altered with hypothyroidism. Replacement of thyroid hormone causes this fluid, which only amounts to a few pounds, to dissipate over a few weeks. Most cases of hypothyroidism are actually discovered long before myxedema even develops, which is why the majority of people experience little, if any, weight loss after treatment. The effect of hypothyroidism on weight has been vastly blown out of proportion to reality."

The study, "Effect of Levo-Thyroxine Treatment on Weight and Body Mass Index in Children with Acquired Hypothyroidism," was co-authored by Dr. W. Jackson Smith, associate professor of pediatrics and chief of pediatric endocrinology at UK, and Maysa El-Sayyid, a medical student at UK.