Correlation of dietary iron intake and serum iron with thyroid stimulating hormone (TSH) and free thyroxine (FT4) levels in adult hyperthyroid patients

Abstract

Abstract Objectives National Baseline Health Research 2013 showed that there were 706,757 (0.4%) hyperthyroid patients in Indonesia. Hyperthyroidism is characterized by abnormal thyroid stimulating immunoglobulin (TSI) which causes low TSH and high FT4 levels. Hyperthyroid patients have a decrease of serum iron levels due to acute phase reactions of hyperthyroidism. This study aimed to analyze the correlation between dietary iron intake and serum iron with TSH and FT4 levels in adult hyperthyroid patients. Methods This study was conducted in February–July 2020 at the Clinic of Magelang Health Research and Development Center. Sampling of this cross sectional study was based on inclusion criteria in order to obtain 50 adult hyperthyroid patients. Dietary iron intake was collected with 2 × 24 h dietary recall, serum iron was measured with colorimetric analysis, the levels of TSH and FT4 were measured by ELISA. The collected data were analyzed using Spearman correlation and multivariate linear regression with 95% confidence level. Results Deficiencies of dietary iron intake was found in 20 hyperthyroid patients (40%). Low serum iron levels were found in 10 hyperthyroid patients (20%). Spearman correlation analysis showed that dietary iron intake had a negative correlation with TSH (r=−0.294; p<0.05) but did not correlate with FT4 (r=−0.142; p>0.05), while serum iron didn’t associated with both TSH (r=0.110; p>0.05) and FT4 (r=0.142; p>0.05). Furthermore, regression analysis showed that dietary iron intake, serum iron, phytate, and thyrozol intake correlate with TSH levels (R square=0.193; p<0.05) and FT4 levels (R square=0.341; p<0.05), but there were no independent association between dietary iron intake and serum iron with TSH and FT4 levels (p>0.05). Conclusions Intake and serum of iron didn’t correlate with TSH and FT4 levels in adult hyperthyroid patients.