Familial postpartum transient hyperthyroidism.

Postpartum painless thyroiditis with transient hyperthyroidism is being recognized with increasing frequency. Evidence tends to support an autoimmune cause. We treated a 33-year-old woman who experienced typical postpartum painless thyroiditis. Her sister had had a similar episode 13 years previously, and their mother had had postpartum hyperthyroidism 42 years earlier. We believe that this familial association provides further support for autoimmunity in postpartum thyroiditis.