What is the best course of action for a 25-year-old woman with elevated Thyroid-Stimulating Hormone (TSH) levels and normal Thyroxine (T4) levels who wants to get pregnant?

From the Guidelines

For a 25-year-old woman with elevated TSH and normal T4 levels who wants to get pregnant, treatment with levothyroxine is recommended to minimize the risks of miscarriage, preterm birth, and developmental issues in the baby. This recommendation is based on the possible association between high TSH and increased fetal wastage or subsequent neuropsychological complications occurring in the offspring due to thyroid insufficiency 1. The goal is to normalize TSH levels to below 2.5 mIU/L before conception and maintain this level during pregnancy.

• Key considerations for treatment include:
  • Starting levothyroxine at a dose of 50-75 mcg daily, taken on an empty stomach 30-60 minutes before breakfast
  • Monitoring TSH levels every 4-6 weeks until stable, then every trimester during pregnancy, with dose adjustments as needed
  • Increasing levothyroxine requirements by 25-50% during pregnancy, as the requirement for levothyroxine in treated hypothyroid women frequently increases during pregnancy 1
  • Taking prenatal vitamins containing folic acid, but separating these from levothyroxine by at least 4 hours to avoid interference with thyroid hormone absorption
• It is essential to monitor women on thyroid replacement therapy and educate them about its impact on pregnancy, as women who are adequately treated before pregnancy and those diagnosed and treated early in pregnancy have no increased risk of perinatal morbidity 1.

From the FDA Drug Label

Hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, pre-eclampsia, stillbirth and premature delivery. Maternal hypothyroidism may have an adverse effect on fetal and childhood growth and development. Since elevations in serum TSH may occur as early as 4 weeks gestation, pregnant women taking Levothyroxine Sodium Tablets, USP should have their TSH measured during each trimester. An elevated serum TSH level should be corrected by an increase in the dose of Levothyroxine Sodium Tablets, USP

The best course of action for a 25-year-old woman with elevated Thyroid-Stimulating Hormone (TSH) levels and normal Thyroxine (T4) levels who wants to get pregnant is to give thyroxine now (hypothyroid), as hypothyroidism during pregnancy is associated with a higher rate of complications.

• Key points:
  • Elevated TSH levels should be corrected before pregnancy
  • Hypothyroidism during pregnancy can have adverse effects on fetal and childhood growth and development
  • Thyroxine treatment should be initiated to prevent these complications 2
  • Levothyroxine therapy should not be discontinued during pregnancy, and hypothyroidism diagnosed during pregnancy should be promptly treated 2

From the Research

Thyroid-Stimulating Hormone (TSH) Levels and Pregnancy

• A 25-year-old woman with elevated TSH levels and normal Thyroxine (T4) levels who wants to get pregnant should be managed carefully to prevent adverse effects on both mother and fetus 3.
• The American Thyroid Association guidelines recommend that women with subclinical hypothyroidism (SCH) should be treated with levothyroxine to achieve a normal TSH level 4.

Levothyroxine Treatment

• Levothyroxine treatment can be initiated at a dose of 50 mcg/day, but the dose may need to be adjusted based on TSH levels 5, 4.
• A study found that 57.4% of women with SCH were thyroid peroxidase antibody positive, and the median gestational age at the initiation of levothyroxine treatment was nine weeks 4.
• The risk of gestational diabetes mellitus was significantly higher in women with SCH, but the risks of miscarriage, gestational hypertension, intra-uterine growth restriction, low birth weight, and preterm birth were not significantly higher 4.

TSH Level Monitoring

• TSH levels should be monitored every 4 weeks through midgestation to identify abnormal values 6.
• A trimester-specific TSH lower reference range of 0.1 mIU/liter can be used to identify patients who require dose reduction 6.
• Women with treated hypothyroidism should increase their levothyroxine dose by two tablets/week once pregnant to prevent maternal hypothyroidism 6.

Management Options

• Option A: Give thyroxine now (hypothyroid) - this may be necessary if the woman's TSH levels are elevated and she is planning to become pregnant 3, 4.
• Option B: Give thyroxine during pregnancy - this may be necessary if the woman's TSH levels become elevated during pregnancy 3, 6.
• Option C: Follow Up - regular monitoring of TSH levels is necessary to adjust levothyroxine doses and prevent adverse effects on mother and fetus 3, 4, 6.
• Option D: Proceed to pregnancy without any treatment - this is not recommended as untreated hypothyroidism can cause adverse effects on both mother and fetus 3.