Clinical Thyroidology® for the Public

Summaries for the Public from recent articles in Clinical Thyroidology
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HYPOTHYROIDISM
No benefit of levothyroxine in women with recurrent pregnancy loss with normal thyroid function despite positive thyroid antibodies

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BACKGROUND
Miscarriage or pregnancy loss is unfortunately relatively common and can occur in about 2 to 3% of pregnancies. Untreated hypothyroidism is a risk factor for miscarriage and this increased risk is reduced by treatment with levothyroxine. The presence of thyroid antibodies, specifically thyroid peroxidase antibody (TPO) is also one of the factors associated with pregnancy loss, even when the thyroid levels are normal. TPO antibodies are a marker for autoimmune thyroid disease and is the antibody found in patients with Hashimoto’s thyroiditis. It is not clear that treatment with thyroid hormone prevents miscarriage in women with thyroid autoimmunity alone. This study was done to find out if treatment with thyroid hormone in women with history of previous pregnancy losses and TPO antibodies but normal thyroid function helps prevent miscarriage.

THE FULL ARTICLE TITLE
 Van Dijk MM et 2022 Levothyroxine in euthyroid thyroid peroxidase antibody positive women with recurrent pregnancy loss (T4LIFE trial): A multicentre, randomized, double-blind, placebo-controlled, phase 3 trial. Lancet Diabetes Endocrinol. Epub 2022 Mar 14. PMID: 35298917.

SUMMARY OF THE STUDY
A total of 187 women between 18 and 42 years old, from 15 different hospitals in Denmark, Netherlands and Belgium participated in the study. All women had a history of pregnancy loss (two or more pregnancy losses). They had normal levels of thyrotropin hormone (TSH) indicative of normal thyroid function and positive TPO antibodies. The participants were divided in two groups. One group received levothyroxine at a dose according to their weight and level of TSH. The other group received placebo (no medication). The average age in both groups was similar: 34.9 years old for the treated group and 33.7 years old for the placebo group. TSH levels were also similar in both groups. At the end of the study there was no difference in live birth rates (babies born after 24 weeks of gestation), pregnancy loss, or preterm birth (birth before 37 weeks’ gestation) between the two groups of patients.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study confirms previous studies showing that treatment with thyroid hormone in women with history of pregnancy loss and TPO antibodies but normal thyroid function does not prevent miscarriage. Based on the current scientific evidence, thyroid hormone treatment should not be routinely offered to pregnant women with normal thyroid function.

— Susana Ebner MD

ABBREVIATIONS & DEFINITIONS

Hypothyroidism: a condition where the thyroid gland is underactive and doesn’t produce enough thyroid hormone. Treatment requires taking thyroid hormone pills.

Hashimoto’s thyroiditis: the most common cause of hypothyroidism in the United States. It is caused by antibodies that attack the thyroid and destroy it.

Levothyroxine (T4): the major hormone produced by the thyroid gland and available in pill form as Synthroid™, Levoxyl™, Tirosint™ and generic preparations.

TSH: thyroid stimulating hormone — produced by the pituitary gland that regulates thyroid function; also the best screening test to determine if the thyroid is functioning normally.

TPO antibodies: these are antibodies that attack the thyroid instead of bacteria and viruses, they are a marker for autoimmune thyroid disease, which is the main underlying cause for hypothyroidism and hyperthyroidism in the United States.

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