Does your surrogate candidate have a Thyroid Disorder? Here’s what you need to know about their medical screening if you’re unsure about whether your surrogate candidate will be recommended to move forward with a surrogacy journey by a maternal-fetal medicine physician.

Thyroid & Fertility

Thyroid hormones (T3 and T4) interact directly with your reproductive system. When these levels are off, it disrupts the communication loop between your brain and your ovaries. The key concern for a surrogate could be Implantation Failure. Thyroid hormones are necessary to make the uterine lining “receptive” to an embryo.

The pituitary gland in your brain makes TSH (thyroid-stimulating hormone), which tells your thyroid how hard to work.

Two main thyroid problems affect fertility:

• Hypothyroidism – underactive thyroid (high TSH, low or low-normal T4)
• Hyperthyroidism – overactive thyroid (low TSH, high T4/T3)

Good News! Thyroid disorders are highly manageable and often not a deterrent for an MFM recommendation to move forward with a surrogacy journey.

1. Optimization of TSH Levels

If a surrogate goes to their primary care doctor or OB/GYN, they may be told that their TSH (Thyroid Stimulating Hormone) is normal if it is below 4.5 or 5.0 mIU/L.

However, “Normal for Life” is not “Normal for Pregnancy.” A Maternal-Fetal Medicine doctor may convey different information. When trying to conceive, you MFM may aim for a TSH level below 2.5 mIU/L. This can be managed with medication (usually Levothyroxine) before getting pregnant. 

2. Managing Medication Safety

• Hypothyroidism: Levothyroxine is essentially a replacement for the hormone your body isn’t making. It is safe to take while trying to conceive. It helps reduce the risks associated with pregnancy for a surrogate.
• Hyperthyroidism: If a surrogate candidate has Graves’ disease, they may need to switch medication. Methimazole is common, but we often switch patients to Propylthiouracil (PTU) or strictly monitor Methimazole doses during the first trimester to minimize risks to the embryo. This switch should happen before a surrogate gets pregnant.

Manageable Risks for a Surrogate

During an MFM screening, these are the most common risks that we are looking to prevent for a potential surrogate.

• Miscarriage: This is the most immediate risk. Thyroid hormone is vital for the early survival of the pregnancy. Untreated hypothyroidism significantly increases the rate of first-trimester loss.
• Neurodevelopmental Issues: In the first 12 to 18 weeks of pregnancy, the baby has no functioning thyroid of its own. It relies entirely on yours for brain development. Severe, untreated hypothyroidism in the mother has been linked to lower IQ and developmental delays in children.
• Preeclampsia and Preterm Birth: Both uncontrolled hypo- and hyperthyroidism increase the stress on the mother’s cardiovascular system, raising the risk of high blood pressure (preeclampsia) and delivering the baby too early.