Metformin ameliorates insulin resistance, thyroid nodules and thyroid function

Objective: To evaluate the ameliorative impact of metformin on insulin resistance (IR), as well as thyroid nodules (TNs) and function in TN patients with IR. Methods: The clinical data of 128 TN patients with IR admitted to Yantai Laiyang Central Hospital from July 2018 to March 2020 were retrospectively analyzed and categorized into a control group (CNG, n = 64) and a study group (SG, n = 64). Patients in the CNG received standard lifestyle intervention, while those in the SG received standard lifestyle intervention in conjunction with metformin therapy for 1 year of course. Weight-related indicators, IR, thyroid function, TN diameter, and oxidative stress levels were compared between the two groups before and after treatment. Additionally, the safety of metformin was evaluated. Results: Before treatment, no significant differences were observed between the two groups in fasting plasma glucose (FPG), 2-h postprandial glucose (2hPG), glycated hemoglobin (HbA1c), fasting insulin (FINS), homeostatic model assessment of insulin resistance (HOMA-IR), systolic blood pressure (SBP), diastolic blood pressure (DBP), thyroid-stimulating hormone (TSH), malondialdehyde (MDA), TN diameter, and thyroid volume (P > 0.05). After treatment, significant statistical differences were observed in the aforementioned indicators between the two groups (P < 0.05). After 1 year of treatment, the SG exhibited lower levels of FPG, 2hPG, HbA1c, FINS, HOMA-IR, SBP, DBP, TSH, MDA, TN diameter, and thyroid volume, and showed higher levels of HOMA-beta, superoxide dismutase, and glutathione peroxidase levels compared to before treatment (P < 0.05). The incidence of adverse reactions in the SG was significantly higher than that in the CNG (P < 0.05). Taking metformin and free thyroxine (FT4) were protective factors for TSH (P < 0.05). Conclusion: Metformin could significantly improve IR and oxidative stress levels, regulate TSH levels, and shrink TNs in TN patients with IR, with high safety. The administration of metformin and FT4 were identified as protective factors for positive prognosis.