BIRMINGHAM, United Kingdom — Taking levothyroxine with thyroid peroxidase (TPO) antibodies but a normal thyroid function does not increase the likelihood of delivering a live baby, according to the TABLET trial.

What is the TABLET trial and why is it important?

The thyroid is a butterfly-shaped gland located on the front of the neck, and secretes thyroid hormone. Thyroid hormone circulates throughout the blood, regulates metabolism and plays an important role in reproductive function.

Thyroid peroxidase (TPO) antibodies, develop when the immune system attacks the thyroid itself. One in 10 women with normal thyroid function have TPO antibodies. Previous research showed TPO antibodies are associated with an increased risk of miscarriage and preterm birth.

During pregnancy, there is an increase demand for thyroid hormone. The presence of TPO antibodies during pregnancy can lower levels of thyroid hormones in the body. Some doctors treat women who have TPO antibodies with thyroid hormone (levothyroxine) when trying to conceive and during pregnancy hoping to improve their chances of having a baby. Nevertheless, the evidence to support this approach was weak.

The TABLET (Thyroid Antibodies and LEvoThyroxine) trial was a large multicentre, well-designed study. The study involved 940 women with at least one previous miscarriage or undergoing fertility. All women tested positive for TPO antibodies but had normal thyroid hormone levels.

Women were randomly assigned to receive 50 microgram of oral levothyroxine daily or a daily placebo before they conceived. Treatment continued until the end of the pregnancy.

What are the findings and what do they mean?

Pregnancy outcomes, including pregnancy loss, preterm birth rate, and neonatal outcomes were the same for both groups.


Two hundred and sixty-six (56.6%) women in the levothyroxine group and 274 (58.3%) women in the placebo became pregnant. One hundred and seventy-six  (37.4%) women taking levothyroxine and 178 (37.9%) women taking a placebo, had a live baby after at least 34 weeks gestation.

Levothyroxine should not be recommended in clinical practice to improve conception and live birth rates.

Unlike previous studies, this trial was high-quality involving a large number of participants across different centre in the UK. Levothyroxine did not improve pregnancy success for women with TPO antibodies and normal thyroid hormones levels.

The lead study author said:

This was a monumental trial. We screened nearly 20,000 women. It took us nearly 10 years. We could do this because the miscarriage clinical and research community is an exemplary one! I am really proud to be part of it. We will continue to look for ways to help the many women and couples who suffer the devastation of miscarriges.

Professor Arri Coomarasamy

The authors concluded that the use of levothyroxine should not be recommended in clinical practice to improve conception and live birth rates.

Source:

The original study was published in the New England Journal of Medicine

Professional Opinion

Views from Twitter

Miscarriage Association on Twitter: “The TABLET trial results show that Levothyroxine didn’t reduce the risk of miscarriage in euthyroid women with thyroid antibodies and a history of miscarriage or infertility. https://t.co/5pEX8R8New / Twitter”

The TABLET trial results show that Levothyroxine didn’t reduce the risk of miscarriage in euthyroid women with thyroid antibodies and a history of miscarriage or infertility. https://t.co/5pEX8R8New

Professor Arri Coomarasamy MBChB MD FRCOG FMedSci on Twitter: “Agree Cathy. Even in the subgroup with TSH > 2.5 (and upto the trial cut off of 3.63), there wasn’t the tiniest bit of benefit. We must really stop giving thyroxine to these women. The message needs to get out to fertility specialists who are busy titrating LT4 to get TSH <2.5! / Twitter"

Agree Cathy. Even in the subgroup with TSH > 2.5 (and upto the trial cut off of 3.63), there wasn’t the tiniest bit of benefit. We must really stop giving thyroxine to these women. The message needs to get out to fertility specialists who are busy titrating LT4 to get TSH <2.5!

Authors

Jhia Teh
Executive Editor

Fifth year medical student at Imperial College London with a BSc in Reproductive and Developmental Sciences. Academic interests include: Reproductive health, gynaecological surgery and medical education. Avid runner on the side.