Hypothyroidism: up levothyroxine dose after pregnancy confirmed.(Obstetrics)

ALEXANDRIA, VA. -- Women of reproductive age who have clinical hypothyroidism should be counseled to increase their levothyroxine by two doses per week as soon as pregnancy is confirmed and to have their thyroid-stimulating hormone levels checked as soon as possible, Dr. P. Reed Larsen said at a symposium sponsored by the American Thyroid Association.

The two additional doses equal an increase of about 30% in levothyroxine (LT4) intake--enough to offset the increased thyroxine need that has been shown to arise in half of pregnant women by the eighth gestational week, said Dr. Larsen of Harvard Medical School, Boston.

A growing body of evidence suggests that maternal hypothyroidism in the first trimester puts the fetus at increased risk for neurodevelopmental abnormalities, including a decreased IQ.

Preconceptional counseling is necessary because most women, even if they regularly see an endocrinologist for their thyroid condition, don't seek specific counsel on the subject when they conceive, Dr. Larsen said. "Everyone's excited about a new pregnancy, and calling the endocrinologist about their thyroid hormone dose isn't tops on their list of things to do."

Even a 30% increase in LT4 may not be enough to ...