High rate of persistent hypothyroidism in a large-scale prospective study of postpartum thyroiditis in southern Italy.
J Clin Endocrinol Metab. 2011 ,96(3):652-7.
Limited data exist concerning the hormonal status of women with PPT at the end of the first postpartum year. The authors conducted a large prospective study of the incidence and clinical course of PPT. The study was conducted at two ambulatory clinics in southern Italy, an area of mild iodine deficiency. A total of 4394 women were screened for thyroid function and thyroid auto-antibodies at 6 and 12 months postpartum. Women were classified as being at high or low risk of having thyroid disease before any thyroid testing. Incidence, clinical presentation, and course of postpartum thyroiditis were assessed. Postpartum thyroiditis (hypothyroidism and or hyperthyroidism) developed in 3.9% (169 of 4384). Women classified as being at high risk for thyroid disease had a higher incidence of PPT than women classified as low risk (11.1 vs. 1.9%; odds ratio, 6.69). Eighty-two percent of the 169 women with PPT had a hypothyroid phase during the first postpartum year. At the end of the first postpartum year, 54% of the 169 women had persistent hypothyroidism. Conclusions: One of every 25 pregnant women in southern Italy developed PPT. Women at high risk for thyroid disease have an increased rate of PPT. The high rate of permanent hypothyroidism at 1 yr should result in a reevaluation of the widely held belief that most women with PPT are euthyroid at the end of the first postpartum year.
As noted by J Lazarus in a related editorial comment (JCEM 96,p614,2011), in this large and carefully done study the incidence of PPT was at the lower end of many series reporting from 4-9% incidence. Noteworthy was the especially high incidence of presumed permanent hypothyroidism (54%) seen at 12 months post-partum. Sixty percent of cases were among those classified as clinically at high-risk for PPT, but 40% would be missed if this categorization was used for testing. L De Groot