The effect of Metformin treatment in obese insulin-resistant patients with euthyroid goiter

Effects of Slow-Acting Metformin Treatment on the Hormonal and Morphological Thyroid Profile in Patients with Insulin Resistance

Metformin appears to reduce TSH levels in untreated hypothyroid patients. In contrast, in euthyroid patients with type 2 diabetes mellitus (T2DM), metformin is initially devoid of effects on TSH. However, it is followed by a significant reduction in TSH level after twelve months of treatment. Additionally, some evidence suggests that metformin may also improve thyroid morphological abnormalities. This study aimed to evaluate the effects of metformin not only on TSH and thyroid hormone values, but also on thyroid volume and nodules. A total of 50 patients (mean age: 36.9 ± 12.8 years) with insulin resistance (homeostatic model assessment (HOMA) index ≥2.5) and with thyroid uninodular disease were recruited for this study. They were prescribed slow-acting metformin at a daily dose of 500 mg for six months. Treatment with metformin in euthyroid patients with uninodular thyroid disease and insulin resistance reduces TSH levels, increases FT4 and FT3 values, and decreases thyroid and nodule volumes. These data suggest that metformin may be an effective drug not only for the treatment of T2DM and metabolic syndrome, but also for thyroid disease.

Subclinical hypothyroidism has no association with insulin resistance indices in adult females: A case-control study

Longitudinal studies have indicated an association between thyroid function and insulin resistance (IR) or a neutral relationship. Both the lowest tertile of free thyroxine (fT4) and the highest tertile of free triiodothyronine (fT3) were found to be associated with IR in cross-sectional studies. The aim of the present study was to analyze the association between IR and subclinical hypothyroidism in a female adult population from Bucharest, Romania. This is a retrospective pilot case-control study that included female patients examined by two endocrinologists and a diabetologist in an outpatient clinic. The retrospective follow-up had a one-year duration and included the evaluation of thyroid function tests and IR indices based on fasting insulinemia and C-peptide. The study included 176 women, 91 with subclinical hypothyroidism, with a median age of 60±17 years and a mean body mass index (BMI) of 27.79±4.76 kg/m². The majority of the population (50%) was diagnosed with autoimmune thyroiditis, and 17.05% with goitre. The univariate logistic regression using hypothyroidism as the explaining variable found no evidence of a significant relationship between a decreased thyroid function and IR (OR 1.32; P=0.36). Metabolic syndrome was probably the most important determinant of IR in the population group studied. Thus, it was not the thyroid function per se, but the coexistence of other elements of this syndrome that prevailed in determining IR. Advantages to the study are the design that permitted evaluation of IR and the thyroid function at different moments in time as well as the uniformity of the blood tests. The multivariate analyses were adjusted for age, lipid profile and treatment; however, one limiting factor was the absence of other hormonal blood tests. In summary, there was no association between the thyroid function tests (TSH, fT4) and IR indices in adult Romanian women in a case-control study with one-year retrospective follow-up.