TSH-lowering effect of metformin in type 2 diabetic patients: Differences between euthyroid, untreated hypothyroid, and euthyroid on L-T4 therapy patients

Carlo Cappelli, Mario Rotondi, Ilenia Pirola, Barbara Agosti, Elena Gandossi, Umberto Valentini, Elvira De Martino, Antonio Cimino, Luca Chiovato, Enrico Agabiti-Rosei, Maurizio Castellano

Research output: Contribution to journalArticle

Abstract

OBJECTIVE - To assess the interplay between metformin treatment and thyroid function in type 2 diabetic patients. RESEARCH DESIGN AND METHODS - The acute and long-term effects of metformin on thyroid axis hormones were assessed in diabetic patients with primary hypothyroidism who were either untreated or treated with levothyroxine (L-T4), as well as in diabetic patients with normal thyroid function. RESULTS - No acute changes were found in 11 patients with treated hypothyroidism. After 1 year of metformin administration, a significant thyrotropin (TSH) decrease (P <0.001) was observed in diabetic subjects with hypothyroidism who were either treated (n = 29; from 2.37 ± 1.17 to 1.41 ± 1.21 mIU/l) or untreated (n = 18; 4.5 ± 0.37 vs. 2.93 ± 1.48) with L-T4, but not in 54 euthyroid subjects. No significant change in free T4 (FT4) was observed in any group. CONCLUSIONS - Metformin administration influences TSH without change of FT4 in patients with type 2 diabetes and concomitant hypothyroidism. The need for reevaluation of thyroid function in these patients within 6-12 months after starting metformin is indicated.

Original languageEnglish
Pages (from-to)1589-1590
Number of pages2
JournalDiabetes Care
Volume32
Issue number9
DOIs
Publication statusPublished - Sep 2009

ASJC Scopus subject areas

  • Internal Medicine
  • Endocrinology, Diabetes and Metabolism
  • Advanced and Specialised Nursing

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    Cappelli, C., Rotondi, M., Pirola, I., Agosti, B., Gandossi, E., Valentini, U., De Martino, E., Cimino, A., Chiovato, L., Agabiti-Rosei, E., & Castellano, M. (2009). TSH-lowering effect of metformin in type 2 diabetic patients: Differences between euthyroid, untreated hypothyroid, and euthyroid on L-T4 therapy patients. Diabetes Care, 32(9), 1589-1590. https://doi.org/10.2337/dc09-0273