Metformin affects thyroid function in male rats

Abstract

An intriguing area of research in type 2 diabetes recently discovered association of metformin therapy with thyroid functional and morphological changes. We aimed to evaluate the external symptoms and biochemical indicators concerning thyroid function in rats treated with metformin. Male wistar rats were randomly divided into four groups: Group (D–/M–), Group (D–/M+), Group (D+/M–), and Group (D+/M+), according to whether they were induced to diabetic model or placed on metformin. Characteristics of food intake, body weight, and other external symptoms were recorded. Thyroid function, concluding serum thyrotropin (TSH), free triiodothyronine (FT3), free thyroxine (FT4), were measured. We found a significantly higher TSH and lower FT4 in rats in Group (D+/M–), compared with rats in Group (D–/M–), but no significant change in FT3 level. Rats on metformin treatment exhibited relatively lower body weight and symptoms like irritability and diarrhea, concomitant with marked increase in FT3 and FT4 , no matter if they were induced to diabetic model or not . A slight but significant reduction in TSH concentration was also observed in rats received metformin. These data reveal that metformin can modify thyroid function with corresponding clinical symptoms of hyperthyroidism in male rats. Metformin's contribution to suppress TSH and increase FT3, FT4 should arise our attention to its treatment interference in clinical practice.

Both Matricaria chamomilla and Metformin Extract Improved the Function and Histological Structure of Thyroid Gland in Polycystic Ovary Syndrome Rats through Antioxidant Mechanism

“…Treatment of PCOS rats with metformin significantly ameliorated the hypothyroid function as confirmed by the decreased TSH and improved T3 and T4 hormones relative to PCOS rats. The results were in agreement with those of Xiaowen et al [28], who reported that that metformin may directly affect the synthesis of thyroid hormone and then decrease the level of TSH. It has been demonstrated that metformin crosses the blood-brain barrier and a central mechanism of TSH inhibition may thus be an attractive explanation.…”

The Predictive Role of Thyroid Hormone Levels for Early Diabetic Retinal Changes in Experimental Rat and Human Diabetes

“…Consistent with another study on STZ-diabetic rats, only fT4 and not fT3 levels showed changes in the present study. 53 Furthermore, interestingly and unexpectedly, the connection between fT4 levels and dual cone numbers was not monotonic as originally assumed. Instead, our results indicate that the number of dual cones in the diabetic rat retina increases in the case of both higher and lower fT4 levels than the control average.…”

The effect of Central and peripheral thyroid resistance indices on diabetic retinopathy: a study of hospitalized euthyroid patients with T2DM in China

“…(3) The association between low levels of free THs and microangiopathy may be attributed to the impairment of vascular function, which is characterized by a decrease in the availability of nitric oxide (NO). This vascular dysfunction leads to alterations in renal hemodynamics, glomerular filtration, and disrupted autoregulation [ 25 ]. (4) Czarnyojtek showed that patients with TD exhibited elevated levels of C-reactive protein (CRP), which could potentially contribute to the onset and progression of DR [ 26 ].…”