What is the management of hypothyroidism in a 9-week pregnant patient with a recent Thyroid-Stimulating Hormone (TSH) level of 1.19, currently on 75 micrograms of Synthroid (levothyroxine)?

From the Guidelines

Your current TSH level of 1.19 while taking 75 mcg of Synthroid is within the normal range for pregnancy, which is good news, and I recommend continuing your current dose but getting your thyroid levels checked again in 4 weeks, then every 4-6 weeks throughout pregnancy. During pregnancy, thyroid function should be monitored more frequently as requirements often increase 1. For women with pre-existing hypothyroidism, it is essential to maintain optimal thyroid levels to support fetal brain development, especially in the first trimester. The target TSH during pregnancy is typically between 0.1-2.5 mIU/L in the first trimester, so your current level is appropriate. Some key points to consider:

• Thyroid hormone is crucial for fetal brain development, especially in the first trimester 1.
• Your body's demand for thyroid hormone naturally increases during pregnancy due to increased blood volume, placental metabolism of thyroid hormone, and transfer of thyroid hormone to the developing fetus.
• About 25-50% of women with hypothyroidism need dose increases during pregnancy, so regular monitoring is essential to ensure optimal levels are maintained throughout your pregnancy 1. It is also important to note that hypothyroidism in the first trimester is associated with cognitive impairment in children, and hypothyroidism (clinical and subclinical) in pregnant women increases the risk of preterm birth, low birth weight, placental abruption, and fetal death, but 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

For pregnant patients with pre-existing hypothyroidism, measure serum TSH and free-T4 as soon as pregnancy is confirmed and, at minimum, during each trimester of pregnancy. In pregnant patients with primary hypothyroidism, maintain serum TSH in the trimester-specific reference range The recommended daily dosage of levothyroxine sodium tablets in pregnant patients is described in Table 3. Pre-existing primary hypothyroidism with serum TSH above normal trimester- specific range Pre-pregnancy dosage may increase during pregnancy Increase levothyroxine sodium dosage by 12. 5 to 25 mcg per day. Monitor TSH every 4 weeks until a stable dose is reached and serum TSH is within normal trimester-specific range.

The patient's current TSH level is 1.19, which is within the normal range for the first trimester of pregnancy. No dosage adjustment is necessary at this time. However, it is essential to continue monitoring TSH levels every 4 weeks to ensure that the patient remains euthyroid throughout the pregnancy 2.

From the Research

Hypothyroidism and Pregnancy

• A recent TSH level of 1.19 on 75 mcg Synthroid indicates that the patient's hypothyroidism is being managed with levothyroxine replacement therapy 3.
• For women with hypothyroidism who become pregnant, it is recommended to increase their weekly dosage by 30% up to nine doses per week, followed by monthly evaluation and management 3.
• Given that the patient is currently 9 weeks pregnant, it is essential to monitor their TSH levels closely and adjust the levothyroxine dosage as needed to ensure optimal management of their hypothyroidism.

TSH Levels and Levothyroxine Dosage

• The patient's current TSH level of 1.19 is within the normal range, indicating that their hypothyroidism is being adequately managed with the current levothyroxine dosage 4, 5.
• However, it is crucial to note that TSH levels can fluctuate during pregnancy, and regular monitoring is necessary to ensure that the patient's hypothyroidism remains well-managed 3, 6.
• The goal of levothyroxine replacement therapy is to maintain a normal TSH level, which can help reduce the risk of death associated with hypothyroidism 6.

Management of Hypothyroidism during Pregnancy

• The management of hypothyroidism during pregnancy requires close monitoring of TSH levels and adjustment of levothyroxine dosage as needed 3, 7.
• It is essential to balance the need to maintain normal TSH levels with the potential risks of over-treatment or under-treatment of hypothyroidism during pregnancy 4, 5.
• Regular evaluation and management by a healthcare provider are crucial to ensure optimal outcomes for both the mother and the fetus.