According to the 2011 "Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and Postpartum," about 25% of women have what's considered "classical" postpartum thyroiditis -- where a period of hyperthyroidism is followed by a period of hypothyroidism, and then normalization of thyroid function within the first year. The hyperthyroid phase typically occurs between 2 and 6 months postpartum, and usually resolves on its own. The hypothyroid phase typically occurs from 3 to 12 months postpartum.
Some 32% of women with thyroiditis have isolated postpartum hyperthyroidism, and 43% have thyroiditis with isolated postpartum hypothyroidism. An estimated 10% to 20% of women who have postpartum thyroiditis that manifests as hypothyroidism end up with permanent hypothyroidism.
Postpartum thyroiditis develops in a third to half of women who have thyroid antibodies in the first trimester, compared to approximately 8% of all pregnant women. Postpartum thyroiditis is more common in women who have other autoimmune disorders. For example: 25% of women who have Type 1 diabetes mellitus or chronic viral hepatitis develop postpartum thyroiditis; 14% of women with lupus develop it; and it affects 44% of women with a prior history of Graves' disease. Having postpartum thyroiditis in a previous pregnancy means a woman has a 70% chance of developing it in subsequent pregnancies.
Postpartum Thyroiditis and Postpartum DepressionAccording to the Guidelines, research results are mixed, but some studies have shown a significant association between postpartum thyroiditis and postpartum depression. The Guidelines recommend that women with postpartum depression should have thyroid stimulating hormone (TSH), free thyroxine (Free T4), and thyroid peroxidase antibody (TPOAb) tests performed.
Typically, antithyroid drugs are not recommended for the hyperthyroid period of postpartum thyroiditis. If women are symptomatic, a beta blocker may be used: the recommended is propranolol, at the lowest possible dose to relieve symptoms.
The Guidelines recommend that after the hyperthyroid phase, TSH should be monitored every two months until 1 year postpartum, to screen for hypothyroidism.
If symptoms are severe, or if conception is being attempted, a woman in the hypothyroid phase of postpartum thyroiditis should be treated. If a woman is asymptomatic, the Guidelines recommend having TSH rechecked every four to eight weeks.
In a woman who is being treated for the hypothyroid phase of postpartum thyroiditis, how long the treatment should continue is determined by whether she is attempting pregnancy, pregnant again, or breastfeeding, in which case, continued treatment is recommended. Otherwise, the Guidelines recommend that the treatment be tapered down within 6 to 12 months after the start of treatment, and potentially discontinued.
The Guidelines recommend that any woman with a prior history of postpartum thyroiditis have an annual TSH test performed to evaluate for permanent hypothyroidism.
Stagnaro-Green, Alex, et. al. "Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and Postpartum." Thyroid. Volume 21, Number 10, 2011 (Online)