Managing Thyroid Hormone Levels in Pregnancy

Thyroid hormone plays a critical role during pregnancy both in the development of a healthy baby and in maintaining the health of the mother. Read about functions of the thyroid gland.

Women with thyroid problems need to understand thyroid’s effect on pregnancy. Also, throughout pregnancy, it is necessary to monitor the thyroid function and take the required medications.

Effect of Pregnancy on Thyroid Function

Two pregnancy-related hormones- human chorionic gonadotropin (hCG) and estrogen cause an increase in thyroid hormone levels in the blood. So in a way HCG is similar to TSH and mildly stimulates the thyroid to produce more thyroid hormone. Whereas, increased estrogen produces higher levels of thyroid-binding globulin, a protein that transports thyroid hormone in the blood.

These hormonal changes are considered to be normal.The thyroid enlarges slightly in all pregnant women, but not enough to be detected by a physical exam. A noticeably enlarged thyroid can be a sign of thyroid disease and should be evaluated.

Diagnosing Thyroid Disorders in Pregnancy

Thyroid problems are difficult to diagnose in pregnancy. This is because of the following reasons:

  • Since a normal pregnancy can also have slightly elevated levels of thyroid hormones, just measuring hormonal levels is not diagnostic.
  • Symptoms of both pregnancy and thyroid disorders are somewhat common, like fatigue, weakness.

Thyroid hormone is critical to normal development of the baby’s brain and nervous system. During the first trimester, the fetus depends on the mother’s supply of thyroid hormone, which comes through the placenta. At around 12 weeks, the baby’s thyroid begins to function on its own.

Types of Thyroid Problems

Hypothyroidism in Pregnancy: Read to understand how to manage low thyroid hormone levels during pregnancy.

Hyperthyroidism in Pregnancy : Read to understand how to manage elevated thyroid hormone levels during pregnancy.

Medical Advice (Q&As) on “Managing Thyroid Hormone Levels in Pregnancy

  1. Shagun

    I am 31 years old. I conceived in Feb 2013 and after 8 weeks had a missed abortion. I am having hypothyroidism. Also, when I conceived TSH was 2.56. When I got my TSH checked for the first time it was 11.46. I am taking 25 mg thyroxine tablet.

    I am worried as this was my first pregnancy. Will I be able to conceive without complications? When should I try again? What precautions should I take? Please suggest. I want to get pregnant as soon as possible.

    1. Buddy M.D. Post author

      Thyroid hormone is very vital for the normal brain development of the fetus. This mainly happens in the first trimester.

      In the first 10 to 12 weeks of gestation, the thyroid gland of the baby is not fully developed, so it is dependent on the mother for its supply of this hormone.

      In a hypothyroid state of the mother, adequate hormone is not available to meet baby’s growth. This may lead to abortion.

      You will definitely be able to conceive again. The only thing is that your pregnancy needs close monitoring. It has to be managed in such a way that there is enough thyroxine available for you and the baby, without any toxicity.

      Before conceiving again, let your TSH value come low. It is recommended that TSH should be kept below 2.5 mIU/L prior to conception. This lowers the risk of the TSH elevating in the first trimester.

      During the first trimester, the TSH level should be maintained at a level between 0.1 and 2.5 mIU/L, 0.2 to 3.0 mIU/L during the second trimester, and 0.3 to 3.0 mIU/L in the third trimester. This is achieved by continuously adjusting the dose of the medicines being taken.

      So, your gyne would be required be keep a close eye over your hormonal levels throughout pregnancy, may be after every 4 to 6 weeks. Also, fetal development would require more frequent assessment by ultra sound.

      Are you positive for thyroid antibodies? If yes, even with normal TSH levels in the early stages of pregnancy, there is a risk of becoming hypothyroid later during term. So, one has to be even more careful.

      Read more on hypothyroidism and fetal development.

  2. Riklia

    Hi There, I am 5 weeks pregnant, I was put on lowest dose of 25 mg of levothyroxine prior to conceiving & my levels ranged from 1.6 – 1.9.
    my thyroid got tested as soon as I found out at 4 weeks pregnant & tsh was 2.56. My fertility consultant said as it’s only just over the 2.5 optimum threshold that all I need to do is take an extra 25mg every other day. I am now worried whether I am taking enough, and whether I should be doubling my dose instead of taking extra dose every other day. When can I retest? I don’t want to wait another 3 weeks if there’s a risk I’m not getting enough thyroxine at this critical time. Should I just double my dose? Would really appreciate any advice. Many thanks


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