Thyroid disorders during pregnancy

Thyroid disorders are amongst the most prevalent endocrine dysfunctions of women in their reproductive phase. During pregnancy the demand for thyroid hormones increases. Iodine deficiency during pregnancy can result in hypothyroidism. The WHO recommends a dietary allowance of 200 mug Iodine daily during pregnancy. Even under adequate iodine supply, subclinical hypothyroidism due to Hashimoto's thyroiditis is detected in up to 2.5% of pregnant women. Untreated overt hypothyroidism during pregnancy results in neuropsychointellectual impairment of the offspring. Manifest hyperthyroidism develops in 0.2% of pregnant women, in >90% of these women due to Grave's disease. Untreated hyperthyroidism during pregnancy due to Grave's disease leads to a high risk of preterm delivery, low birth weight, and eclampsia and therefore must be treated with propylthiouracil. In the first trimester transient gestational hyperthyroidism can develop that spontaneously resolves during the second trimester with decreasing levels of choriogonadotropin levels and mostly does not require therapy. In up to 10% of pregnancies postpartum thyroiditis develops which can result in transient mild hyperthyroidism in the postpartal period and leads to permanent hypothyroidism in up to 30% of the afflicted women.