Related Experiment Video
Updated: May 21, 2026

Homogeneous Time-resolved Förster Resonance Energy Transfer-based Assay for Detection of Insulin Secretion
Published on: May 10, 2018
Thyreotropin levels in diabetic patients on metformin treatment
Carlo Cappelli1, Mario Rotondi, Ilenia Pirola
1Endocrine and Metabolic Unit, Department of Medical and Surgical Sciences, Clinica Medica, University of Brescia, c/o 1 Medicina Spedali Civili Piazzale Spedali Civili 1, 25100 Brescia, Italy. cappelli@med.unibs.it
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 (M-/L-), 119 subjects never treated with metformin and L-T(4); Group (M+/L-), 203 subjects who started metformin treatment at recruitment; and Group (M+/L+), 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 M+/L+, TSH significantly decreased independently from the basal level (Q1, from 1.450.53 to 1.011.12 mU/L (P=0.037); Q2, from 3.600.53 to 1.910.89 mU/L (P<0.0001)). In M+/L group, the decrease in TSH was significant only in those patients with a basal high-normal serum TSH (Q2: from 3.24±0.51 to 2.27±1.28 mU/l (P=0.004)); in M-/L- patients, no significant changes in TSH levels were observed. In patients of group M+/L 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 +: from 3.38±0.48 to 1.87±1.08 mU/l (P<0.001); Q2 AbTPO -: from 3.21±0.52 to 2.34±1.31 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.
Related Concept Videos
Oral Hypoglycemic Agents: Biguanides and Glitazones
Hypoglycemia
Insulin: Dosing Regimen and Adverse Effects
The basal dose constitutes about 40%-50% of the total daily dose, with the rest as premeal insulin. The mealtime insulin dose should mirror...
Hypoglycemia and Glucagon
Type II Diabetes Mellitus III: Clinical Manifestations and Diagnosis
Hyperglycemia

