Effect of metformin on thyroid function tests in patients with subclinical hypothyroidism: an open-label randomised controlled trial
Though most of the observational studies have shown that metformin can reduce serum thyroid stimulating hormone (TSH) level in patients of hypothyroidism with diabetes or polycystic ovarian disease, randomised controlled trials are sparse. The primary objective of this study was to evaluate the effect of metformin on thyroid function tests (TSH, free T4, and free T3) in patients with subclinical hypothyroidism (SCH).
In this open label, parallel arm, randomised controlled trial, 60 patients of SCH (TSH 5.5–10 mIU/L) were randomised to either metformin group (1500 mg/day) or control group.
A total of 46 patients (23 in each group) completed the study and no significant difference in serum TSH, free T4 or free T3 was found in between the 2 groups. Neither there was any significant change in serum TSH, free T4 or free T3 (pre and post 6 months) within the individual groups. However, the rate of normalisation of serum TSH in patients with negative thyroid antibody was significantly higher than patients with positive thyroid antibody (71.4% vs. 18.8%; P = 0.026) in metformin group in post hoc analysis. Fasting plasma glucose, serum high-density lipoprotein and indices of insulin sensitivity significantly improved in metformin group. Four patients (17%) had mild gastrointestinal adverse effects in the metformin group.
We did not find any significant change in thyroid function test in patients with SCH with metformin therapy.
KeywordsAdipokines Insulin resistance Metformin Subclinical hypothyroidism
- Anti-Tg Ab
- Anti-TPO Ab
Anti-thyroid peroxidase antibody
Body mass index
Diastolic blood pressure
Homeostasis Model Assessment for 2 Insulin Resistance
Polycystic ovarian disease
Quantitative Insulin Sensitivity Check Index
Randomised controlled trial
Systolic blood pressure
Thyroid function test
Thyroid stimulating hormone
This study was done from intramural research fund (Grant number: JIP/Res/Intra-DM-MCH/phs1/01/2016-17 Project number 37) of Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), India.
Compliance with ethical standards
Conflict of interest
The authors declare that there is no conflict of interests.
This study was done with approval of Institute ethical committee.
Informed consent was obtained from all individual human participants included in the study.
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