Clinical Thyroidology® for the Public

Summaries for the Public from recent articles in Clinical Thyroidology
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THYROID AND PREGNANCY
Postpartum thyroiditis in women with euthyroid and hypothyroid Hashimoto’s thyroiditis prior to pregnancy

CTFP Volume 14 Issue 1

BACKGROUND
Postpartum thyroiditis is a short lived inflammation in thyroid gland that occurs in the first year after pregnancy. It is estimated to happen after 8% of pregnancies. In this condition, a course of hyperthyroidism (1 – 3 months after delivery) is followed by 6-12 months of hypothyroidism, then thyroid function returns to normal. Women may have just the hyperthyroid phase, just the hypothyroid phase, or both phases.

While postpartum thyroiditis usually occurs in women with previously normal thyroid function during pregnancy, it may also occur in mothers who suffer from hypothyroidism before pregnancy. In the United States, Hashimoto’s thyroiditis is the most common cause of hypothyroidism. This diagnosis is made with positive thyroid peroxidase (TPO) antibodies in the setting of hypothyroidism. However, not all patients with Hashimoto’s thyroiditis are hypothyroid; some have normal thyroid function despite positive TPO antibodies and do not need yet need to take thyroid hormone.

The goal of this study was to evaluate the frequency of postpartum thyroiditis in women with Hashimoto’s thyroiditis with and without hypothyroidism before pregnancy.

THE FULL ARTICLE TITLE
 Moleti M et al 2020; Postpartum thyroiditis in women with euthyroid and hypothyroid Hashimoto’s thyroiditis antedating pregnancy. J Clin Endocrinol Metab. Epub 2020 Apr 17. PMID: 32301483.

SUMMARY OF THE STUDY

This study was done in Italy. The medical records of 1378 women from 2008 to 2017 visits in a university hospital were reviewed. A total of 167 women with Hashimoto’s thyroiditis who became pregnant during the study time were included; 98 were on thyroid hormone before pregnancy and 69 had normal thyroid hormone level before pregnancy.

Overall, 65 women (38.9%) developed postpartum thyroiditis; this occurred more commonly in women with Hashimoto thyroiditis who did not need to take thyroid hormone before pregnancy than in hypothyroid women.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
Women with Hashimoto thyroiditis who are not hypothyroid before pregnancy are at increased risk of developing postpartum thyroiditis after childbirth. This study suggests that physicians and patients should be aware of this increased risk in the postpartum period. However, the number of cases reviewed in this study was relatively small and conclusion should be confirmed by subsequent studies.

— Shirin Haddady, MD MPH

ABBREVIATIONS & DEFINITIONS

Postpartum thyroiditis: an inflammation of the thyroid in women who have just delivered a baby. The inflammation first causes mild hyperthyroidism for 1-3 months after delivery. This is followed by hypothyroidism starting 4-6 months after delivery. The hypothyroidism resolves and normal thyroid function returns 12-18 months after delivery in most women. While many women have both the hyperthyroid and the hypothyroid phase, some women may only have one or the other.

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

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

Euthyroid: a condition where the thyroid gland as working normally and producing normal levels of thyroid hormone.

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