Hyperthyroidism in pregnancy: achieve euthyroid status as early as possible.(Obstetrics)

ALEXANDRIA, VA. -- Achieving euthyroid status as early in pregnancy as possible--and ideally, before conception--is crucial in preventing maternal and fetal complications from maternal hyperthyroidism.

Uncontrolled hyperthyroidism in pregnancy is rare, but its consequences are serious. Dr. Jorge Mestman said at a symposium sponsored by the American Thyroid Association.

The relative risk of prematurity can soar to as much as 16 times the rate seen in the general population if maternal hyperthyroidism isn't controlled during gestation. In addition, there are both a 9-fold increase in the relative risk of low birth weight and a 5-fold increase in the relative risk of severe preeclampsia. Central congenital hypothyroidism in the neonate is also a possible complication, said Dr. Mestman, director of the diabetes and metabolic diseases center at the University of Southern California in Los Angeles.

Severe, uncontrolled maternal hyperthyroidism may result in maternal congestive heart failure, thyroid storm, or placental abruption: the infant may be stillborn or have thyroid dysfunction.

The relative risks of these outcomes are still elevated--although not as dramatically--in women whose hyperthyroidism is controlled sometime during the pregnancy, he said at the symposium, which was also sponsored by the American Association of Clinical Endocrinologists.

Most women with poorly controlled or uncontrolled hyperthyroidism have preexisting conditions, such as Graves' disease or toxic adenoma. However, a hyperthyroidism of pregnancy called gestational transient thyrotoxicosis (GTT) occurs in as many as 15% of otherwise normal pregnancies. It is more common in women who are pregnant with multiples and is related to inappropriate secretion of HCG. This is a self-limited condition that needs no antithyroid medication.

The diagnosis of GTT is a clinical one, Dr. Mestman said; thyroid tests will show low serum TSH and a normal or elevated free [T.sub.4] level. Patients with Graves' disease will have had prepregnancy symptoms that will continue and perhaps increase during pregnancy; women with GTT will have had ...