HONOLULU — Hypothyroidism has only a minor effect on weight gain, and correcting it does not result in significant weight loss, according to the findings of an observational study.
“[Physicians] have been trained that hypothyroidism causes weight gain and any child who is overweight needs to have hypothyroidism ruled out,” said the study's investigator Dr. Paul Kaplowitz, chief of the division of endocrinology at Children's National Medical Center, Washington, D.C.
“In fact, hypothyroidism causes very minor weight gain and does not cause the kind of obesity that we're seeing so commonly in our young patients. [With] a child who is 20, 30, 50 pounds overweight, hypothyroidism should not be very high on your list,” he said in an interview about the poster, which he presented at the joint meeting of the Pediatric Academic Societies and the Asian Society for Pediatric Research.
Dr. Kaplowitz and his colleague, Dr. Melissa Crocker, studied 29 moderate to severe hypothyroid and 57 hyperthyroid children referred for an initial evaluation between March 2004 and October 2007. Weight and height measurements were made at diagnosis, at the first follow-up 1–4 months after initiating therapy, and at a second follow-up at about month 6 (hyperthyroid) or month 11 (hypothyroid).
At the first follow-up, the 26 hypothyroid children receiving treatment (mean age 10.7 years) had lost an average of 0.4 kg, exactly the same amount as the 3 uncorrected hypothyroid children. At the second follow-up, the euthyroid children had gained an average of 2.0 kg while the uncorrected children had gained 0.6 kg.
Since some of this weight gain could have been explained by natural or catch-up growth, the investigators looked at the change in the standard deviation of the children's body mass index. This turned out to be -0.2 for the euthyroid children and -0.5 for the uncorrected children, which was not significantly different.
Dr. Kaplowitz said the most interesting observation was that there was no significant difference in the body mass index between the hyperthyroid and hypothyroid patients at diagnosis. “It's variable in both groups. The difference between the two is very small relative to the difference within each group.”
The mean BMI of the 57 hyperthyroid children was 21.1 kg/m
Dr. Kaplowitz said that thyroid testing might be appropriate if the child had additional symptoms beyond weight gain. “The most common symptom of hypothyroidism was feeling fatigued, but feeling colder and more depressed and decreased appetite were also common.”
However, if a patient is losing weight, “think about hyperthyroidism and see if they have any of these suggestive signs: feeling hot, doing poorly in school, enlarged thyroid. Definitely hyperthyroidism should be considered if they're losing weight and have any other symptoms.”
The investigators said that they had no conflicts of interest to declare.
Hypothyroidism causes very minor weight gain and does not cause the kind of obesity so commonly seen in young patients. DR. KAPLOWITZ