The Relationship between Serum Iron and Thyroid Function in the Patients with Type 2 Diabetes.

PURPOSE

Our primary objective in this study is to determine the relationship between serum iron (Fe) and thyroid functions in type 2 diabetes mellitus (T2DM) patients.

MATERIALS AND METHODS

Glucose metabolic parameters, trace elements, such as Fe, and thyroid functions for 1657 type 2 diabetic patients treated at the Shanghai Pudong Hospital's Department of Endocrinology from 2018 to 2021 were assessed.

RESULTS

Variations in free thyroid hormones (FTH) and total thyroid hormones (TTH) were insignificant; however, thyroid-stimulating hormone (TSH) levels were markedly elevated in patients with positive thyroid peroxidase antibody (TPOAb) and/or positive antithyroglobulin antibody (TgAb) (p<0.05). Additionally, gender disparities affected FTH levels (p<0.05) but not TTH and TSH levels. The female gender was significantly negatively correlated with serum Fe levels (r=-0.381, p<0.05). Serum Fe deficiency also had an effect on FT3 in both genders, FT4 and TT4 in males (p<0.05), but not TSH (p>0.05). The multilinear regression model showed that TT3 (β=0.702), eGFR (β=0.109), Fe (β=0.003), female gender (β=-0.061), and age (β=-0.061) were the major determinants for FT3 change. Moreover, renal function, which was represented as the estimated glomerular filtration rate (eGFR), had no effects on Fe and TSH levels but on the levels of FTH and TTH (p<0.05). FT3/FT4 exhibited correlations with Fe (r=0.252) and eGFR (r=0.285). Finally, changes in Fe levels had no significant impact on fasting plasma glucose (FPG), fasting C-peptide, HbA1c, and glycated albumin levels (p>0.05).

CONCLUSION

In addition to age, gender, and renal functions, serum Fe levels in T2DM patients have a significant relationship with thyroid functions.