BMI in those under 21 associated with thyroid cancer

Aug. 27, 2021

Children and young adults who are obese are at greater risk for malignant thyroid nodules, according to new study from Monroe Carell Jr. Children’s Hospital at Vanderbilt. 

The study, Evaluation of Thyroid Nodule Malignant Neoplasms and Obesity Among Children and Young Adults, was published in JAMA Network Open.

With the incidence rate of thyroid cancer increasing in children over the last two decades, a team of Vanderbilt researchers wanted to explore possible causes, including various socioeconomic factors along with puberty, ethnicity, and body mass index z-scores (used for children, and also known as BMI-for-age percentile).

“Over the last 20 to 30 years, our institution’s number of cases of pediatric thyroid nodules has stayed relatively the same from year to year, but there has been a rise in cancer rates, and we wondered why,” said Ryan Belcher, MD, MPH, Assistant Professor of Pediatric Otolaryngology — Head and Neck Surgery, a study author. “The one thing that kept popping up in our analysis of our cases of malignancy was the BMI.”

Other previous analyses, including one published in the American Cancer Society’s Cancer journal, have shown that the incidence of pediatric thyroid cancer has been increasing by 4.43% yearly in an examination of data tracked from 1998 to 2013. This trend has continued in recent studies, Belcher noted.

For the retrospective, cross-sectional study, Belcher and a team of Vanderbilt researchers, trainees, and biostatisticians, collected a large cohort of pediatric thyroid patients from Children’s Hospital. This cohort included 116 patients under age 21 who had thyroid surgery between 2003 and 2019.

The team found that of the 116 patients in the study, 55 had malignant nodules with an average BMI z-score for that cohort of 1.4, while the other 61 patients, who had benign nodules, averaged about half that with a median z-score of 0.7. In children, a BMI z-score of 1.65 or greater is considered obese. In the group with malignant nodules, the scores went as high as 2.4.

The team initially wondered if obesity was simply delaying the ability to detect thyroid nodules on physical exam. However, there was no significant correlation between nodule size and BMI z-score. Most thyroid masses in children are first discovered during a child’s annual routine physical with their pediatrician.

Typically, the child is asymptomatic. Children with a suspected growth are referred to an otolaryngology-head and neck surgeon or endocrine surgeon and endocrinologists to determine if the growth is benign or malignant. Weiss and Belcher are both part of the newly formed Pediatric Thyroid Nodule and Cancer Program at Children’s Hospital, which was developed to improve the coordination of care of these pediatric patients and to improve their outcomes.

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