What should be done for a patient with high TSH and normal T4 who wants to get pregnant?

Management of High TSH with Normal T4 in a Patient Planning Pregnancy

For a 25-year-old recently married woman with high TSH, normal T4 who wants to get pregnant, thyroxine treatment should be initiated immediately to normalize TSH levels before conception. 1

Diagnosis and Classification

• This patient has subclinical hypothyroidism, defined by elevated TSH with normal free T4 levels 1
• Subclinical hypothyroidism is common, with chronic autoimmune (Hashimoto) thyroiditis being the most frequent cause in the United States 1
• Risk factors for elevated TSH include female sex, advancing age, white race, type 1 diabetes, family history of thyroid disease, and previous hyperthyroidism 1

Treatment Recommendations

• Levothyroxine therapy should be initiated immediately before pregnancy rather than waiting until pregnancy occurs 1
• The goal of treatment is to normalize TSH levels before conception to optimize both maternal and fetal outcomes 1
• Starting dose is typically 1.6 mcg/kg/day for patients without risk factors 2
• For this patient planning pregnancy, treatment is particularly important as hypothyroidism during pregnancy is associated with higher rates of complications including spontaneous abortion, pre-eclampsia, stillbirth, and premature delivery 3

Monitoring During Pregnancy

• Once pregnant, TSH levels should be measured during each trimester 3
• An elevated TSH level during pregnancy should be corrected by increasing the dose of levothyroxine 3
• After delivery, the levothyroxine dosage should return to the pre-pregnancy dose 3
• A serum TSH level should be obtained 6-8 weeks postpartum to ensure appropriate dosing 3

Rationale for Treatment

• Untreated hypothyroidism (even subclinical) during pregnancy may have adverse effects on fetal and childhood growth and development 3
• Maternal hypothyroidism increases risk of pregnancy complications 1
• Elevations in serum TSH may occur as early as 4 weeks gestation, making pre-conception normalization of thyroid function optimal 3
• Treatment is particularly important in women planning pregnancy as thyroid hormones are essential for normal fetal brain development 1

Special Considerations

• If both adrenal insufficiency and hypothyroidism are present, steroids should always be started prior to thyroid hormone to avoid an adrenal crisis 1
• Thyroid antibody testing (TPO) may be warranted to identify autoimmune thyroiditis 1
• Certain foods and medications may affect levothyroxine absorption, requiring dosage adjustments (soybean flour, cotton seed meal, walnuts, dietary fiber) 3
• Levothyroxine should be taken on an empty stomach, typically 30-60 minutes before breakfast, for optimal absorption 3

Follow-up

• Regular monitoring of TSH levels is essential during pregnancy 3
• Thyroid function tests should be repeated every 4 weeks until the TSH level is stable 1
• After delivery, continue monitoring as postpartum thyroiditis may occur 1

By initiating levothyroxine treatment before pregnancy, this patient will have the best chance for a successful pregnancy outcome with minimal risk to both mother and fetus.