Thyroid Function Changes During Pregnancy: Key Concerns

Q: Thyroid Function Changes During Pregnancy: Key Concerns

There are many factors to consider regarding thyroid diseases, and the complexities increase during pregnancy. <br>It is recommended that you schedule a follow-up appointment to discuss this with your attending physician without delay. <br>This is the most timely and effective wa

Is there a trend for hypothyroidism to progress to hyperthyroidism?

Hello Doctor: I am currently 34 weeks pregnant.
At the end of May this year, I had my thyroid function tested at the hospital, and the blood test results were as follows: Free T4: 0.79 (normal range: 0.89-1.76), TSH: 3.55 (normal range: 0.55-4.78), Anti-TPO: 28 (<60).
The doctor informed me that I have hypothyroidism and started me on "Eltroxin" 75 micrograms per day (to be taken until the end of June, for a total of one month).
In late June, I had a follow-up test, and the results were: Free T4: 1.43 (normal range: 0.89-1.76), TSH: 0.18 (normal range: 0.55-4.78).
The doctor then increased the dosage to 100 micrograms per day, which I need to take for another month (continuing Eltroxin until the end of July).
I would like to ask the following questions:
1.
The data from June shows that Free T4 has risen to within the normal range, but TSH has dropped significantly below the lower limit.
Does this condition still indicate hypothyroidism?
2.
Does the increase in Eltroxin dosage from 75 to 100 micrograms indicate that my condition has worsened or improved? If my condition has improved, why does the dosage still need to be increased? (I understand that different doctors have different considerations, and I would like to hear your perspective first.)
3.
Given that TSH dropped significantly in June and the medication dosage was increased, is there a risk that TSH will drop even lower in July, and that Free T4 may exceed the upper limit (potentially leading to hyperthyroidism)? Is there a possibility that my attending physician has prescribed an excessive dosage?
4.
After giving birth, if I choose to breastfeed, can I continue taking Eltroxin, or should I temporarily stop the medication and treat my thyroid condition later when I am not breastfeeding?
5.
Since I have hypothyroidism, what is the likelihood that my baby will have congenital hypothyroidism? Is there a chance of avoiding this condition? I did not think of these questions immediately during my follow-up appointment at the end of June, and my next appointment is not until the end of July.
Therefore, I wanted to seek clarification in advance through this platform.
Thank you for your time and guidance!

Jojo, 30~39 year old female. Ask Date: 2018/07/11

Dr. Lin Jianliang reply Internal Medicine

There are many factors to consider regarding thyroid diseases, and the complexities increase during pregnancy.
It is recommended that you schedule a follow-up appointment to discuss this with your attending physician without delay.
This is the most timely and effective way to address your concerns.
Thank you for your message.

Reply Date: 2018/07/11

More Info

Understanding thyroid function changes during pregnancy is crucial for both maternal and fetal health. Thyroid hormones play a vital role in regulating metabolism, growth, and development, particularly during pregnancy when the demand for these hormones increases. Your situation, as described, raises several important concerns regarding thyroid function and its implications for your health and that of your baby.

1. Thyroid Hormone Levels and Diagnosis: Your initial test results indicated low Free T4 levels (0.79) and a normal TSH (3.55), which led to a diagnosis of hypothyroidism. After treatment with levothyroxine (昂特欣), your Free T4 levels improved to 1.43, but your TSH dropped significantly to 0.18. This low TSH level suggests that your thyroid hormone levels are now adequate or even elevated, which can indicate a transition towards hyperthyroidism if the TSH continues to drop. In general, a low TSH in the context of normal Free T4 levels can be a sign of over-treatment, especially in the context of thyroid hormone replacement therapy.

2. Medication Adjustment: The increase in your levothyroxine dosage from 75 to 100 micrograms does not necessarily indicate that your condition has worsened; rather, it reflects the need to maintain optimal thyroid hormone levels during pregnancy. The goal is to ensure that Free T4 remains within the normal range, as both under-treatment and over-treatment can have adverse effects. It is not uncommon for dosages to be adjusted during pregnancy due to the increased metabolic demands and changes in hormone levels.

3. Risk of Hyperthyroidism: Your concern about potentially becoming hyperthyroid due to the increased dosage of levothyroxine is valid. If your TSH continues to decrease and Free T4 levels rise above the normal range, it could indicate hyperthyroidism. Regular monitoring of your thyroid function tests is essential to avoid this scenario. Your healthcare provider should be vigilant in adjusting your medication based on these results to prevent any complications.

4. Postpartum Considerations: After delivery, it is generally safe to continue taking levothyroxine while breastfeeding, as it does not significantly affect breast milk and is considered safe for nursing mothers. However, your healthcare provider may want to reassess your thyroid function postpartum, as the hormonal changes after childbirth can affect your thyroid status.

5. Congenital Hypothyroidism Risk: Regarding your concern about the risk of your baby developing congenital hypothyroidism, it is important to note that while there is a genetic component to thyroid disorders, the overall risk is relatively low. Routine newborn screening for congenital hypothyroidism is performed in many countries, which helps in early detection and treatment if necessary. Your healthcare provider can give you more specific information based on your family history and thyroid condition.

In conclusion, it is essential to maintain regular follow-ups with your healthcare provider to monitor your thyroid function throughout your pregnancy and postpartum period. Adjustments to your medication should be made based on your test results, and any concerns regarding your health or your baby's health should be discussed promptly with your physician. This proactive approach will help ensure the best outcomes for both you and your child.

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