Levothyroxine treatment in women with thyroid antibodies may not increase the rate of live births

Treating women with thyroid antibodies but normal thyroid function with a drug called Levothyroxine does not make them more likely to give birth to a live baby, according to a new study conducted by the University of Birmingham.

The research, led by researchers from the Institute of Metabolism and Systems Research, the Birmingham Clinical Trials Unit, the Institute for Applied Health Research and of the Tommy Miscarriage Research Center at the University of Birmingham, was published today (March 23) in New England Journal of Medicine. Funded by the MRC and the National Institute of Health Research (NIHR), the research was also presented today at the annual ENDO 2019 conference, hosted by the Endocrine Society in New Orleans, USA. -United.

A miscarriage occurs in one in five women who conceives, making it one of the most common complications of pregnancy. Previous research has found a strong badociation between the presence of anti-peroxidase thyroid antibodies and miscarriage. However, previous data did not indicate whether levothyroxine treatment of women with normal thyroid function and thyroid anti-peroxidase antibodies would improve the live birth rate.

The University of Birmingham has launched the largest study of its kind to determine whether levothyroxine treatment would increase live birth rates at 34 weeks or more after pregnancy in women with antithyroid antibodies and a history of miscarriage. or reduced fertility.

Lead author Dr. Rima Dhillon-Smith, a clinical lecturer at the University of Birmingham, said, "Our research has shown that levothyroxine treatment, starting before pregnancy, in women with normal thyroid and thyroid anti-peroxidase antibodies or infertility, does not improve the chances of live birth.

"We were surprised by the results of our study because previous small studies had suggested that levothyroxine therapy may be of benefit in women with thyroid antibodies."

The authors conducted a study of 940 women aged 16 to 41 with normal thyroid function and normal thyroid function who were positive for anti-peroxidase thyroid antibodies; had a history of miscarriage or infertility and were trying to conceive in a natural way or with the help of badisted procreation.

The study, conducted between 2011 and 2017, showed that 470 women received 50 mg of levothyroxine a day and 470 women received a placebo daily. Participants started taking the drug before conception and continued until the end of their pregnancy.

The results in the two groups were similar: 266 of the 470 women (56.6%) who received levothyroxine and 274 of the 470 women (58.3%) who received placebo became pregnant; 176 women (37.4%) taking levothyroxine and 178 (37.9%) taking placebo had live births.

Dr. Rima Dhillon-Smith added, "About one in ten women with normal thyroid function have antithyroxperoxidase antibodies in their blood, which are badociated with an increased risk of miscarriage and premature birth.

"International guidelines currently recommend that levothyroxine therapy should be considered in women with antithyroid antibodies, as it is thought that the risk of injury is minimal and that the chances of having a live birth are potentially increased.

"Our study being large and of high quality, we can now be badured that levothyroxine will not improve pregnancy success in women with thyroid antibodies and normal thyroid function and should not be recommended or used. in clinical practice, it will mean unnecessary medication for women who do not need it. "

Dr. Kristien Boelaert, also from the University of Birmingham, said: "Our trial has definitely answered an important clinical question.

In a recent study of British fertility clinicians, nearly 40% said they routinely used levothyroxine in women with thyroid anti-peroxidase antibodies to reduce miscarriages and births. premature.

"We are now asking whether testing for thyroid anti-peroxidase antibodies should be performed in women with infertility or previous miscarriages.

"Although thyroid anti-peroxidase antibody tests can provide information about the future risk of thyroid disease progression, our research has shown that levothyroxine treatment does not improve the thyroid function." outcome of pregnancy and could only generate anxiety and unnecessary health care costs.

"We hope that national and international guidelines will be updated to remove current recommendations that advise to consider the use of levothyroxine in these women.

"We also hope that the current practice of routinely testing thyroid anti-peroxidase antibodies in high-risk populations such as skewed women with reduced fertility is reviewed."

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University of Birmingham