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Clinical trial studies the use of Metformin in Women with PCOS


Can taking metformin during pregnancy reduce risk of gestational diabetes and  excessive weight gain?

Polycystic ovary syndrome (PCOS) is a common hormonal disorder affecting women of reproductive age. It is characterized by multiple small cysts in the ovaries, irregular menstrual periods, and high levels of male hormones. Women with PCOS are at higher risk of developing hypothyroidism, a condition in which the thyroid gland doesn't produce enough hormones. Both PCOS and hypothyroidism are associated with adverse pregnancy outcomes, but the interaction between these conditions during pregnancy is not well understood.

A recent clinical trial investigated the thyroid status and its association with pregnancy complications in women with PCOS, and in relation to metformin treatment. Metformin is a drug commonly used to treat PCOS, as it can improve insulin resistance and lower blood sugar levels.

The study involved 288 pregnant women with PCOS who were randomized to treatment with metformin or a placebo from the first trimester to delivery. The researchers measured serum levels of thyroid stimulating hormone (TSH) and free thyroxine (fT4) at several points during pregnancy and related them to metformin treatment and pregnancy complications. They also analyzed thyroid peroxidase antibodies (TPO-ab) at inclusion and at gestational week 36.

The results showed that the overall prevalence of subclinical and overt hypothyroidism was low, with 1.5% and 0% of the participants affected, respectively. The TSH level was not affected by metformin, but fT4 was significantly higher in the metformin group, with less decrease throughout pregnancy compared to the placebo group. This suggests that metformin treatment during pregnancy was associated with less decrease in fT4 compared to placebo, while it did not affect TSH.

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Interestingly, a smaller decrease in fT4 during pregnancy was associated with less weight gain and tended to be associated with a lower risk of gestational diabetes. This highlights the potential benefits of maintaining adequate thyroid hormone levels during pregnancy in women with PCOS.


This study provides important insights into the complex interaction between thyroid status, PCOS, and metformin treatment during pregnancy. While the overall prevalence of hypothyroidism was low in women with PCOS, metformin treatment was associated with less decrease in fT4 throughout pregnancy. This may have important implications for pregnancy outcomes, as maintaining adequate thyroid hormone levels during pregnancy could help reduce the risk of gestational diabetes and excessive weight gain.

If you have PCOS and are pregnant or planning to become pregnant, it's important to discuss your thyroid function with your healthcare provider and consider the potential benefits of metformin treatment.

National Library of Medicine, Feb-21-22
ClinicalTrials.gov NCT00159536 and NCT03259919

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This content is for informational and educational purposes only. It is not intended to provide medical advice or to take the place of such advice or treatment from a personal physician. All readers/viewers of this content are advised to consult their doctors or qualified health professionals regarding specific health questions. CenTrial Data Ltd. does not take responsibility for possible health consequences of any person or persons reading or following the information in this educational content. Treatments and clinical trials mentioned may not be appropriate or available for all trial participants. Outcomes from treatments and clinical trials may vary from person to person. Consult with your doctor as to whether a clinical trial is a suitable option for your condition. Assistance from generative AI tools may have been used in writing this article.