Thyroid Therapy for Mild Thyroid Deficiency in Pregnancy

Published research reports have stimulated national and international controversy regarding
the value of maternal thyroxine therapy given to improve neurodevelopment of the fetus in
women with variously defined hypothyroidism. These reports have led to conflicting and
confusing recommendations as to whether or not all pregnant women in the U.S. should be
screened for subclinical hypothyroidism or hypothyroxinemia.

Pregnant women less than 20 weeks gestation will have a blood test to screen for subclinical
hypothyroidism or hypothyroxinemia. If eligible for the trial, patients will receive
levothyroxine or placebo until delivery. Blood draws will be done at monthly study visits and
the dosage will be adjusted based on test results. The children of these patients will have
developmental testing done annually until they are 5 years of age.

Comparison(s): thyroxine supplementation versus placebo given during pregnancy to determine
whether therapy is effective in improving intellectual ability at 5 years of age.

Inclusion Criteria:

- Subclinical Hypothyroidism as defined by an elevated TSH (≥ 3.00 mU/L) and a free-T4
in the normal range (i.e. 0.86 to 1.90 ng/dL) or Hypothyroxinemia as defined by a TSH
in the normal range (0.08 to 2.99 micrometers (mU)/L) and a low free-T4 (<0.86 ng/dL)

- Singleton Pregnancy

- Gestational age at randomization between 8 weeks 0 days and 20 weeks 6 days

Exclusion Criteria:

1. Major fetal anomaly or demise

2. Planned termination of the pregnancy

3. History of thyroid cancer or current thyroid disease requiring medication

4. Diabetes, on medication (insulin, glyburide)

5. Collagen vascular disease (autoimmune disease), such as lupus, scleroderma and
polymyalgia rheumatica, on medication

6. Receiving anticoagulant therapy

7. Depression, currently on treatment with tricyclics or selective serotonin reuptake
inhibitors (SSRIs)

8. Other known serious maternal medical complications including:

1. Chronic hypertension requiring antihypertensive medication (including diuretics)

2. Epilepsy or other seizure disorder, on medication

3. Active or chronic liver disease (acute hepatitis, chronic active hepatitis) with
persistently abnormal liver enzymes

4. Cancer (including melanoma but excluding other skin cancers)

5. Heart disease (tachyrhythmia, class II or greater heart disease or on heart
medication). Mitral valve prolapse without arrhythmia is not an exclusion.

6. Asthma, on oral corticosteroids

9. Known illicit drug or alcohol abuse during current pregnancy

10. Delivery at a non-network hospital

11. Participation in another intervention study that influences maternal and fetal
morbidity and mortality, or participation in this trial in a previous pregnancy

12. Unwilling or unable to commit to 5 year follow-up of the infant