When women think about pregnancy, the thyroid gland is seldom the first thing that leaps to mind. Nestled in the neck, the gland makes hormones that govern metabolism, helping to regulate body weight, heart rate and a host of other factors.
But if the thyroid malfunctions, it can produce too little or too much of these hormones. During pregnancy those conditions, known as hypothyroidism and hyperthyroidism, respectively, may lead to miscarriage, premature birth and pre-eclampsia — and in the case of hypothyroidism, impaired intelligence in the child.
But the big unanswered question — and crux of the debate — is whether treatment would help women with a mild, common form of thyroid deficiency, called subclinical hypothyroidism. For now, medical societies advise testing only high-risk women.
Symptoms of a wayward thyroid can be subtle, and pregnancy can mask them. Fatigue, weight gain and dry skin — all typical in pregnant women — can also result from hypothyroidism, said Dr. Alex Stagnaro-Green, an endocrinologist at Touro University College of Medicine in Hackensack, N.J.
The opposite condition, hyperthyroidism, affects roughly 2 in 1,000 pregnancies. But again, its symptoms — poor sleep, weight loss and nervousness after childbirth — could result from other postpartum conditions. (Renaissance painters unknowingly depicted the link between thyroid problems and pregnancy by showing women with goiters from an overactive thryoid after childbirth.)
Hypothyroidism, which usually arises from underlying autoimmune disease, is the more frequent and worrisome concern. As many as 10 to 20 percent of reproductive-age women test positive for antibodies that attack the thyroid gland and may eventually destroy it. Their risk of miscarriage is doubled.
Studies do suggest that T4-replacement therapy is protective. But few large clinical trials have rigorously tested this intervention in mildly thyroid-deficient women. So far, promising results have come from one major, well-designed Italian study that showed miscarriage and preterm delivery rates dropped sharply when thyroid hormone pills were given to pregnant women who tested positive for thyroid antibodies.
For now, until there is confirmation that treatment truly helps, Dr. Stagnaro-Green said he still favored selective thyroid screening. But he added, “My belief is that data will be forthcoming that will push us towards universal screening.”
Source