Serial occurrence of two types of postpartum thyroid disorders. Usefulness of Tc-99m pertechnetate uptake

A 32-year-old woman with a history of Graves' disease had an episode of thyrotoxicosis 2.5 months after her first childbirth. Because of low thyroidal uptake of Tc-99m pertechnetate, a diagnosis of postpartum painless thyroiditis was made and the patient was observed without medication. After the normalization of serum levels of thyroid hormones, a second wave of thyrotoxic symptoms emerged. This time, the Tc-99m uptake was slightly elevated and the patient was diagnosed to have a relapse of Graves' disease. This case underscores the previously reported notion that thyroidal uptake was indispensable to distinguish these two causes of postpartum thyrotoxicosis.