Relationship between body mass index and external exposure in hyperthyroid patients treated with iodine-131

Abstract

We performed this study to evaluate the correlation between Body Mass Index (BMI) and Exposure Rate (ER) of hyperthyroid patients treated with iodine-131 so that in case of any relationship, we can improve the prescribed dose for the treatment of hyperthyroid patients and its side effects on the body and the environment. In this analytical and cross-sectional study, 30 patients with hyperthyroidism treated with liquid iodine-131 were randomly selected. We recorded demographic indicators (age, height, and weight) and ER. Patients were treated with the activity of 8-29 mCi (mean 14.4 mCi) oral I-131. The external radiation of patients was measured from a distance of one meter parallel to the patient's thyroid gland at intervals of 6 to 24 hours post-iodine-131 administration. ER measurements and other acquired data were statistically analyzed by R software and its methods. Data were normalized using the Shapiro method, and due to the non-normality of the data in the correlation test, the Spearman method was used. The measurements of this study represent two main findings: 1. There is a significant relationship between ER and iodine-131 activity because the observed significance level (P-value =0.002) is smaller than the predicted error value (0.01). 2. There is no significant relationship between ER and BMI because the observed significance level (P-value =0.082) is greater than the predicted error value (0.05). The present study's findings show a negative relationship between BMI and ER. Still, since the P-value is more than 0.05, this relationship is not statistically significant.

Keywords: Hyperthyroidism; body mass index; exposure; iodine-131; radiation.

Figure 1

Variation in external exposure rate with the iodine-131 activity, including the linear regression line.

Figure 2

Height, Weight, Age, Iodine-131 activity, and External exposure rate pair plots.