The Interplay Between High Cumulative Doses of Radioactive Iodine and Type 2 Diabetes Mellitus: A Complex Cardiovascular Challenge.

Starting from the metabolic profile of type 2 diabetes mellitus (T2DM), we hypothesized that the mechanisms of ¹³¹I-induced cardiotoxicity differ between patients diagnosed with differentiated thyroid cancer (DTC) with/without T2DM, with metformin potentially acting as a cardioprotective agent by mitigating inflammation in patients with T2DM. To address this hypothesis, we quantified, using ELISA, the serum concentration of several key biomarkers that reflect cardiac injury (NT-proBNP, NT-proANP, ST2/IL-33R, and cTn I) in 74 female patients with DTC/-T2DM and 25 with DTC/+T2DM treated with metformin. All patients received a cumulative oral dose of 131I exceeding 150 mCi (5.55 GBq) over approximately 53 months. Our results showed the following: (i) In DTC/-T2DM patients, high-cumulative 131I doses promote a pro-inflammatory state that accelerates the development of cardiotoxicity. Monitoring NT-proBNP, ST2/IL-33R, and cTn I in these patients may help identify those at risk of developing cardiac complications. (ii) In patients with DTC/+T2DM, high-cumulative 131I doses lead to the release of NT-proANP (r = 0.63), which signals that the atria are under significant stress. (iii) In patients with DTC/+T2DM, metformin suppresses inflammation, leading to a dose-dependent reduction in cTn I (r = -0.59). Monitoring cTn I and NT-proANP, and considering the use of metformin as part of the therapeutic strategy, could help manage cardiotoxicity in T2DM patients undergoing 131I therapy.