Postpartum autoimmune thyroiditis is well documented after full-term pregnancy and occurs in 3 to 16 percent of women. The same phenomenon, however, has not been clearly associated with early termination of pregnancy. Marqusee and associates report on patients with normal thyroid function before conception or at the time of pregnancy loss who develop thyroiditis within one year of their loss.

Five women with recent pregnancy loss (at five to 20 weeks of gestation) and normal thyroid function before conception were followed for at least 20 months with measurement of thyroid function and antithyroid antibodies. Thyroiditis, defined as transient biochemical hypothyroidism and/or hypothyroidism within one year of pregnancy loss, was diagnosed in all five women. Two patients had subclinical hypothyroidism alone, with elevated thyroid-stimulating hormone levels that resolved within one month. The other three women were diagnosed with hyperthyroidism at three to 11 months after pregnancy loss when they presented with palpitations and tremulousness.

Because of the proximity of the hyperthyroidism to the pregnancy loss and the high likelihood of thyroiditis, patients were not treated with antithyroid medications. Within eight weeks of the diagnosis of hyperthyroidism, all three women became hypothyroid, and all three conceived again during this hypothyroid phase. Two of these women were treated with thyroid supplementation during their pregnancies until after their deliveries and remained euthyroid.

The authors conclude that the immunologic changes resulting from a short-term pregnancy can lead to painless thyroiditis after pregnancy loss. Women who are antithyroid-antibody positive are at greater risk of developing thyroiditis. Women who have had a recent pregnancy loss require evaluation of thyroid function to optimize maternal thyroid hormone levels in early pregnancy.