Subclinical hypothyroidism: no thyroid benefits from metformin

  • Palui R & al.
  • J Endocrinol Invest
  • 24 May 2019

  • International Clinical Digest
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Takeaway

  • Metformin therapy is not associated with significant changes in thyroid function in patients with subclinical hypothyroidism (SCH), according to an open-label, randomized controlled trial.

Why this matters

  • Several observational studies have suggested that metformin can reduce thyroid-stimulating hormone (TSH) levels in patients with hypothyroidism.

Key results

  • Metformin was associated with similar TSH (6.69 vs 6.85 mIU/L; P=.717), free triiodothyronine (2.71 vs 2.69 pg/mL; P=.77), and free thyroxine (0.99 vs 1.02 ng/dL; P=.397) levels as control.
  • Metformin and control were associated with similar rates of serum TSH normalization (34.8% vs 26.1%; P=.52).
  • In patients treated with metformin, patients with negative thyroid antibody had a higher rate of serum TSH normalization than patients with positive thyroid antibody (71.4% vs 18.8%; P=.026).
  • Metformin was associated with improvements in fasting plasma glucose (P=.001), serum high-density lipoprotein cholesterol (P=.014), and indices of insulin sensitivity (P=.047 for Homeostasis Model Assessment 2 for Insulin Resistance; P=.014 for Quantitative Insulin Sensitivity Check Index; P=.018 for Matsuda Index).

Study design

  • 46 patients with SCH (TSH, 5.5-10 mIU/L), 23 who received metformin 1500 mg/day and 23 who did not, were analyzed.
  • Funding: Jawaharlal Institute of Postgraduate Medical Education and Research, India.

Limitations

  • Small patient sample size.
  • Open-label study.