Study Finds No Link Between BMI and Thyroid Cancer in Teens With Nodules

Although obesity is typically linked to the development of many cancers, including thyroid cancer, a cross-sectional study didn’t find this association in adolescents.

Among 362 patients under the age of 19 with thyroid nodules, thyroid cancer wasn’t associated with BMI z score (OR 1.14, 95% CI 0.91-1.43), reported Ari J. Wassner, MD, of Boston Children’s Hospital, and colleagues in JAMA Otolaryngology-Head & Neck Surgery.

However, BMI z score was linked to larger nodule diameter (Spearman r=0.12, 95% CI 0.02-0.23), as well as a greater likelihood of undergoing thyroid surgery (OR 1.32, 95% CI 1.08-1.62).

Looking more closely in a multivariable analysis, having a larger nodule diameter was independently tied to a higher likelihood of requiring thyroid surgery (OR 1.07, 95% CI 1.05-1.09). On the other hand, the likelihood of undergoing thyroid surgery was no longer significantly tied to BMI z score (OR 1.24, 95% CI 0.99-1.54).

“In this cohort, patients with a higher BMI were more likely to undergo thyroid surgery, which may be partly because of the association of increased BMI with larger nodules,” Wassner’s group explained. “We hypothesize that this may reflect greater difficulty in detecting thyroid nodules clinically in children with larger body habitus, leading to delayed diagnosis.”

The group noted that a higher BMI is likely not considered an independent risk factor for thyroid cancer in children with thyroid nodules.

“Routine thyroid examination is important in children, and any nodules detected should be evaluated based on the established risk factors described in current consensus guidelines,” they recommended.

This analysis looked only at patients treated at Boston Children’s Hospital from 1998 through 2020. All patients were evaluated for a non-autonomous thyroid nodule that was 1 cm or larger in diameter. Overall, thyroid cancer was present in 99 of the 362 patients (27%).

“Unresected nodules were considered to be malignant on the basis of cytologic test results or benign on the basis of cytologic test results and a lack of nodule growth for 1 or more years or indeterminate cytologic test results and a lack of growth for 2 or more years,” the group explained. As for resected nodules, the presence of thyroid cancer was assessed histopathologically.

Of the cohort, 80% were girls, and median age was 15.5. The majority were white, and only 21% had multiple nodules. Patients were excluded from this analysis if they carried a genetic risk for thyroid cancer.

Among the total cohort, the largest nodule diameter was a median of 23 mm, and a median of 28 mm among those with thyroid cancer.

Median levels of thyroid-stimulating hormone weren’t different between those with or without thyroid cancer (1.8 mIU/L vs 1.4 mIU/L, respectively). Presence of thyroid cancer also didn’t differ between the sexes or between race/ethnicity.

Wassner and team also performed a sub-analysis, exclusively looking at patients who underwent thyroid surgery (48%), and found that BMI z score still wasn’t significantly linked with the presence of thyroid cancer (OR 0.93, 95% CI 0.68-1.27).

Instead of looking at BMI z score as a continuous variable, the group separately compared patients with a BMI greater than the 95th percentile versus those below. This analysis also resulted in similar findings.

Although these findings contrast with a prior surgical series that did in fact find an association between BMI z score and malignant nodules, Wassner’s group pointed out that prior studies limited to only resected nodules “may be biased by factors that affect the selection of patients for surgery.”