Can Low TSH Levels Affect Birth Control Pill Use?

Can I take contraceptive pills if my TSH level is low?

Hello Doctor, I previously had a habit of taking emergency contraceptive pills.
After stopping the medication last month, my menstruation has not arrived.
After consulting with a gynecologist, I was informed that I have a 4 cm cyst and that I should be monitored in three months.
Blood tests were arranged to check TSH, PRL, FSH, LH, E2, and other hormones.
The results showed that my TSH level was too low, while the others were normal, raising suspicion of hyperthyroidism (however, there is no pain when pressing on my neck, no tremors, and no weight loss; instead, I have gained three kilograms recently.
The only symptoms I have are heat intolerance, excessive sweating, and slightly increased heart rate).
Therefore, I was referred to an endocrinologist.
After the referral, I had additional blood tests for Anti-TPO, Free T4, Free T3, TSH Receptor Ab, GPT, etc., to confirm the cause, but I will only see the report on September 7, so I do not know the results yet.

I would like to ask you: my menstruation has now arrived, and I want to start taking the contraceptive pill on the fifth day of my period, but I am concerned that after my appointment with the endocrinologist on September 7, there may be more blood tests.
I am unsure if taking the contraceptive pill will affect the blood test results.
Will taking the contraceptive pill impact the thyroid tests? Additionally, I would like to know if it is possible to have low TSH levels while having normal T3 and T4 levels.
What could this indicate in terms of potential diseases? Thank you for your time, Doctor!

Niming, 10~19 year old female. Ask Date: 2020/08/28

Dr. Yuan Tianmin reply Breast and Thyroid

An occasional blood test does not necessarily indicate the possibility of hyperthyroidism.
It may require repeated blood tests, especially if you are taking certain medications, and you may need to wait for additional data to determine whether hyperthyroidism is truly present.

Reply Date: 2020/08/28

More Info

Low TSH levels can indeed have implications for various aspects of health, including the use of birth control pills. In your case, it’s important to understand the relationship between thyroid function and hormonal contraceptives, as well as the potential effects of low TSH levels on your overall health.

Firstly, TSH (Thyroid Stimulating Hormone) is produced by the pituitary gland and regulates the production of thyroid hormones (T3 and T4) by the thyroid gland. Low TSH levels typically indicate hyperthyroidism, where the thyroid gland is overactive and produces excessive amounts of thyroid hormones. This condition can lead to symptoms such as weight loss, increased heart rate, sweating, and sensitivity to heat, among others. However, you mentioned that you are experiencing weight gain and other symptoms that do not align with typical hyperthyroidism, which can sometimes complicate the diagnosis.

Regarding your question about the use of birth control pills, hormonal contraceptives can interact with thyroid hormone levels. Some studies suggest that estrogen-containing contraceptives can increase the levels of thyroid-binding globulin (TBG), which may lead to an increase in total T4 levels while free T4 levels remain unchanged. This means that while the total amount of thyroid hormone in the blood may appear elevated, the active form of the hormone (free T4) may not be affected. Therefore, starting a birth control pill like "Yue Ji" (悅己) could potentially influence your thyroid hormone levels, but it is unlikely to directly affect the TSH measurement itself.

However, it is crucial to consider that any hormonal changes in your body, including those induced by birth control pills, may complicate the interpretation of your thyroid function tests. If you start taking the pill before your follow-up appointment on September 7, it could potentially alter the results of your thyroid function tests, making it more challenging for your endocrinologist to assess your thyroid status accurately.

As for the possibility of having low TSH levels with normal T3 and T4 levels, this can occur in certain situations. For instance, it may be seen in subclinical hyperthyroidism, where TSH is suppressed, but T3 and T4 levels remain within the normal range. This condition can arise from various causes, including thyroid nodules or autoimmune conditions like Graves' disease. It’s essential to follow up with your endocrinologist, who may recommend additional tests, such as thyroid antibodies or imaging studies, to determine the underlying cause of your low TSH levels.

In summary, while starting birth control pills may not directly affect the TSH levels, it could complicate the interpretation of your thyroid function tests. It is advisable to wait until after your follow-up appointment and the completion of your blood tests before starting any new medications, including hormonal contraceptives. This will ensure that your healthcare provider has the most accurate information to assess your thyroid function and make informed decisions regarding your treatment plan. Always consult with your healthcare provider before making any changes to your medication regimen, especially in the context of thyroid issues.

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