Transient cold nodule of the thyroid due to localized postpartum thyroiditis.

A 27-year-old woman with no previous personal or family history of thyroid disease was referred to us for the evaluation of thyroid nodule, five months postpartum. Thyroid scintigraphy demonstrated a left cold nodule. Fine needle aspiration cytology of the nodule showed a mixture of colloid, follicular cells and lymphocytes, suggesting lymphocytic thyroiditis. Thyroid function tests were normal and thyroid autoantibodies were negative. After two months the thyroid nodule was not palpated and thyroid scintigraphy returned to normal. Thyroid function tests remained normal twelve months after delivery. These findings suggest that postpartum thyroiditis may present as a localized transient form and should be considered in the differential diagnosis of painless solitary nodule that appears postpartum.