title: Metformin inhibits goitrogenous effects of type 2 diabetes.
abstract: OBJECTIVE
  Data on the association between type 2 diabetes mellitus (T2DM) and thyroid volume are sparse. An experimental study demonstrated an inhibitory effect of metformin on the growth of human thyroid cells. So far no study on humans has investigated potentially modulating effects of metformin on the association between T2DM and thyroid volume. Therefore, we investigated these effects in a population-based cohort study.
  
  
  METHODS
  We used data from the Study of Health in Pomerania and included 2570 individuals for cross-sectional and 1088 individuals for longitudinal analyses. T2DM was defined by physician-diagnosed self-report or intake of antidiabetic medication.
  
  
  RESULTS
  In the cross-sectional data, females with T2DM treated with antidiabetic medication other than metformin had a larger thyroid volume (β=4.69; 95% CI 1.87 to 7.50) and a higher odds ratio (OR) for goiter (OR=1.71; 95% CI 1.05 to 2.79) than females without T2DM, whereas in males, no such association was detected. In females or males treated with metformin, T2DM was not associated with thyroid volume or goiter. In longitudinal analyses, incident T2DM not treated with metformin was significantly associated with a higher risk for incident goiter in the total population (incidence rate ratio (IRR)=1.70; 95% CI 1.10 to 2.91). Individuals with T2DM having changed from metformin to other antidiabetic agents during follow-up also had a higher risk for incident goiter than individuals without T2DM (IRR=2.71; 95% CI 1.74 to 4.20).
  
  
  CONCLUSIONS
  We demonstrate an inhibitory effect of metformin on prevalent and incident goiter. Anti-goitrogenous effects of metformin add to the general benefits of metformin treatment of T2DM.
authors.affiliation: Institute for Community Medicine, University of Greifswald, Greifswald, Germany. till.ittermann@uni-greifswald.de
authors.forename: Till
authors.initials: T
authors.lastname: Ittermann
authors.forename: Marcello R P
authors.initials: MR
authors.lastname: Markus
authors.forename: Sabine
authors.initials: S
authors.lastname: Schipf
authors.forename: Michael
authors.initials: M
authors.lastname: Derwahl
authors.forename: Christa
authors.initials: C
authors.lastname: Meisinger
authors.forename: Henry
authors.initials: H
authors.lastname: Völzke
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D003430:Cross-Sectional Studies; D048909:Diabetes Complications / Q000517:prevention & control*; D003924:Diabetes Mellitus, Type 2 / Q000150:complications* / Q000188:drug therapy*; D005260:Female; D005500:Follow-Up Studies; D005858:Germany / Q000453:epidemiology; D006442:Glycated Hemoglobin / Q000378:metabolism; D006042:Goiter / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control*; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D015994:Incidence; D007328:Insulin / Q000627:therapeutic use; D016014:Linear Models; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D055118:Medication Adherence; D008687:Metformin / Q000627:therapeutic use*; D008875:Middle Aged; D016017:Odds Ratio; D015995:Prevalence; D057566:Self Report; D013961:Thyroid Gland / Q000187:drug effects*; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers; D006442:Glycated Hemoglobin; D007004:Hypoglycemic Agents; D007328:Insulin; D008687:Metformin; C517652:hemoglobin A1c protein, human