Thyreotropin levels in diabetic patients on metformin treatment

Abstract

Objective: A retrospective study to evaluate the changes in TSH concentrations in diabetic patients treated or not treated with metformin and/or L-thyroxine (L-T 4 ). Methods: Three hundred and ninety three euthyroid diabetic patients were divided into three groups on the basis of metformin and/or L-T 4 treatment: Group (MK/LK), 119 subjects never treated with metformin and L-T 4 ; Group (MC/LK), 203 subjects who started metformin treatment at recruitment; and Group (MC/LC), 71 patients on L-T 4 who started metformin recruitment. Results: The effect of metformin on serum TSH concentrations was analyzed in relation to the basal value of TSH (below 2.5 mIU/l (Q1) or between 2.51 and 4.5 mIU/l (Q2)). In patients of group MC/LC, TSH significantly decreased independently from the basal level (Q1, from 1.45G0.53 to 1.01G1.12 mU/l (PZ0.037); Q2, from 3.60G0.53 to 1.91G0.89 mU/l (P!0.0001)). In MC/LK group, the decrease in TSH was significant only in those patients with a basal high-normal serum TSH (Q2: from 3.24G0.51 to 2.27G1.28 mU/l (PZ0.004)); in MK/LK patients, no significant changes in TSH levels were observed.In patients of group MC/LK showing high-normal basal TSH levels, a significant decrease in TSH was observed independently from the presence or absence of thyroid peroxidase antibodies (AbTPO; Q2 AbTPO C: from 3.38G0.48 to 1.87G1.08 mU/l (P!0.001); Q2 AbTPO K: from 3.21G 0.52 to 2.34G1.31 mU/l (P!0.001)). Conclusions: These data strengthen the known TSH-lowering effect of metformin in diabetic patients on L-T 4 treatment and shows a significant reduction of TSH also in euthyroid patients with higher baseline TSH levels independently from the presence of AbTPO.

Metformin and low levels of thyroid-stimulating hormone in patients with type 2 diabetes mellitus

“…Our findings support the hypothesis that metformin may lead to reductions in TSH levels in patients with treated hypothyroidism, [4][5][6][7]22,23 with no effects in euthyroid patients. 3,6,7 In the former group, we found that metformin monotherapy was associated with a 55% increased risk of low TSH levels (0.4 mIU/L), when compared with sulfonylurea monotherapy.…”

“…3,6,7 In the former group, we found that metformin monotherapy was associated with a 55% increased risk of low TSH levels (0.4 mIU/L), when compared with sulfonylurea monotherapy. This finding is concordant with the results of 3 previous studies.…”

“…1 However, despite its excellent safety profile, 2 studies have suggested that its use may lower thyroid-stimulating hormone (TSH) levels in patients with diabetes and hypothyroidism. [3][4][5][6][7][8][9] In some studies, the use of metformin was associated with reductions in TSH levels below the reference range, [4][5][6][7] potentially exposing patients to the harmful consequences of subclinical hyperthyroidism (e.g., cardiovascular conditions and fractures 10 ). In contrast, metformin was not associated with changes to TSH levels in euthyroid patients.…”

Metformin inhibits goitrogenous effects of type 2 diabetes

“…While three studies in patients with hypothyroidism and/or levothyroxine treatment showed a reduction of serum TSH levels under metformin treatment (9,10,11), a retrospective study demonstrated significantly higher serum TSH levels in euthyroid patients with T2DM treated with metformin compared with those treated with other diabetic agents (12). However, in that study, metformin use was not associated with serum TSH levels after adjustment for several potential confounding factors of which goiter was the only significant one (12).…”

Metformin: od mehanizmov delovanja do napredne klinične uporabe

“…Za metformin so pokazali, da zniža serumsko raven tirotropina (TSH) (91). Vpliva tudi na prerazporeditev in zmanjšanje maščobnega tkiva v telesu (12).…”