Postpartum thyroid dysfunction: a viewpoint from Thailand.

Abstract

Postpartum thyroid dysfunction (PPTD) refers to changes in thyroid function that occur during the first 12 months postpartum. The changes in thyroid function can either be thyrotoxicosis or hypothyroidism which may be transient or permanent in nature. The aetiology is multiple, including postpartum thyroiditis, new onset or exacerbation of Graves' disease, exacerbation of primary hypothyroidism due to Hashimoto's thyroiditis, central hypothyroidism due to postpartum pituitary necrosis or central hypothyroidism due to lymphocytic hypophysitis. There is a paucity of data concerning PPTD in South East Asia. However, available data indicate a seemingly high prevalence of central hypothyroidism due to postpartum pituitary necrosis in Thailand. The alterations in the course of Graves' disease during pregnancy and postpartum are similar to those reported elsewhere. However, the dosage of antithyroid drug used during pregnancy in Thai women is quite small. The lower environmental iodine in Thailand may be one of the responsible factors. Interestingly, the prevalence of PPTD due to postpartum thyroiditis reported from Thailand was only 1.1% which was less than that reported in other countries. The discrepancy in the geographic prevalence of postpartum thyroiditis may result from the interaction of immunogenetic heterogeneity of different ethnic background, environmental iodine intake, and other unidentified environmental factors.