Postpartum thyroid dysfunction
Postpartum thyroiditis affects 5 to 10% of women in the postpartum period and is the most common cause of postpartum thyroid dysfunction. Women with a positive TPOAb level have up to a 50% risk of developing postpartum thyroiditis and those with a past history of postpartum thyroiditis have up to a 70% risk.2,17 Postpartum thyroiditis is typically associated with transient hyperthyroidism followed by transient hypothyroidism with eventual return to euthyroidism. A quarter of women with postpartum thyroiditis have isolated hyperthyroidism and half have isolated hypothyroidism.2 Postpartum thyroiditis is a painless thyroiditis and women may be asymptomatic or have only mild symptoms of thyrotoxicosis or hypothyroidism.
In women with postpartum hyperthyroidism the main differential diagnosis is Graves’ disease, which is generally associated with a positive TRAb result and signs such as a goitre with a bruit or ophthalmopathy. In patients who develop thyrotoxicosis after six months’ postpartum, Graves’ disease is the most likely diagnosis. If there is uncertainty about the diagnosis a technetium uptake scan can be performed; however, if the mother is breastfeeding, breast milk will need to be expressed and discarded during the scan and generally for 48 hours afterwards. If antithyroid medication is required for postpartum management of Graves’ disease in breastfeeding mothers, the lowest effective dose should be used and the tablet ingested following a breastfeed. Doses of carbimazole up to 20 mg and propylthiouracil 300 mg daily have been shown to be safe in breastfeeding women with less than 1% of the parent drug being transferred into breast milk.2
Thyroid disorders are common during pregnancy.18,19 Early screening of at-risk women and appropriate treatment can improve pregnancy outcomes. Guidelines on the treatment of subclinical hypothyroidism in pregnancy have recently been updated to account for changes in the evidence base.2 ET