Hypothyroidism - Highlights

Highlights

Hypothyroidism and Heart Disease

• Mildly underactive thyroid (subclinical hypothyroidism) may increase the risk of developing an irregular heart beat (atrial fibrillation), but it is not associated with other heart problems, suggests an important 2006 study in the Journal of the American Medical Association (JAMA).
• Previous studies have indicated that mildly underactive thyroid is associated with coronary artery disease and heart failure. The JAMA study contradicts these findings.
• According to the study’s researchers, there is no increased heart disease risk if mildly underactive thyroid is left untreated.

Pregnancy and Hypothyroidism

• Pregnant women with low thyroid levels have a greater risk for birth defects that affect a child’s mental and developmental health. A 2006 article in Pediatrics suggested that most of these problems occur during the first 3 months of pregnancy.
• Both hypothyroidism and mildly underactive thyroid increase the risk for premature delivery and birth defects.
• The American Thyroid Association recommends that women with a personal or family history of thyroid disease have their thyroid levels tested both before and after they get pregnant.
• During pregnancy, women with hypothyroidism should have their thyroid levels checked at least once per trimester. They may need to have their medication dosage increased.

Congenital Hypothyroidism

The timing and dosage of levothyroxine (T4) treatment is important for babies who are born with hypothyroidism (congenital hypothyroidism). Early and aggressive drug treatment may help lessen mental and developmental problems. However, research also suggests that the effects of congenital hypothyroidism persist over time. Children with milder forms of the disease may have fewer health problems later in life than children with more severe forms.

Drug Interactions

The cancer drug imatinib (Gleevec) may interfere with levothyroxine and worsen hypothyroidism, according to a study in Clinical Pharmacology and Therapeutics.

Review Date: 04/19/2006
Reviewed By: Harvey Simon, M.D., Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital