TSH Levels: Medication Dilemmas in Hyperthyroidism Treatment

Issues related to undetectable TSH levels due to medication?

Hello, doctor.
I have a question I would like your assistance with.
1.
I have been diagnosed with hyperthyroidism and have been on medication for 23 days: methimazole 10mg three times a day and propranolol 10mg once a day.
A few days ago, I returned for a follow-up and reviewed my blood test results.
2.
The doctor mentioned that my T3 and T4 levels have improved, but my TSH is still undetectable (less than 0), so the doctor suggested increasing the methimazole dosage to 20mg in the morning and 20mg in the evening.
3.
I just spoke with a friend who has been practicing medicine in a clinic abroad for 40 years, and he expressed concern, stating that the dosage of methimazole should be reduced rather than increased, and advised me to seek a third opinion.
Could you please help clarify this for me? Thank you!

Michael, 40~49 year old female. Ask Date: 2019/01/05

Dr. Chen Shunfu reply Internal Medicine

This question requires a complete blood test report and a physical assessment to answer.
If you would like to consult further, please make an appointment with Dr.
Li Jian.
If no additional medications or tests are prescribed on that day and only a simple consultation is conducted, there will be no consultation fee.
Thank you.

Reply Date: 2019/01/05

More Info

When it comes to managing thyroid disorders, particularly hyperthyroidism, understanding TSH (Thyroid Stimulating Hormone) levels is crucial. In your case, it appears that you have been diagnosed with hyperthyroidism and are currently on medication, specifically Newmazole (Methimazole) and Inderal (Propranolol). Your recent lab results indicate that while your T3 and T4 levels have improved, your TSH remains undetectable, which is a common scenario in hyperthyroidism.

1. Understanding TSH Levels: TSH is produced by the pituitary gland and regulates the production of T3 and T4 from the thyroid gland. In hyperthyroidism, elevated levels of T3 and T4 suppress TSH production, often leading to very low or undetectable TSH levels. This is a normal physiological response. The fact that your TSH is less than 0 indicates that your thyroid hormone levels are still elevated, which is consistent with hyperthyroidism.

2. Medication Adjustments: Your doctor’s recommendation to increase the dosage of Newmazole to 20 mg twice daily is based on the need to further suppress the production of thyroid hormones. While it may seem counterintuitive to increase the dose when TSH is low, the goal is to bring T3 and T4 levels back into the normal range. In hyperthyroidism, the primary concern is controlling the levels of T3 and T4, and TSH is not typically used as a direct target for treatment adjustments in this context.
3. Consulting with Other Physicians: Your friend’s suggestion to reduce the dosage of Newmazole may stem from a misunderstanding of the treatment goals in hyperthyroidism. In some cases, if TSH is low but T3 and T4 are within normal limits, a reduction in medication may be warranted. However, since your T3 and T4 are still elevated, increasing the dose of Newmazole is a reasonable approach to achieve better control of your thyroid function.

4. Monitoring and Follow-Up: It is essential to have regular follow-ups and lab tests to monitor your thyroid hormone levels and TSH. The treatment for hyperthyroidism often requires adjustments based on these levels. Your healthcare provider will likely want to see how your body responds to the increased dosage of Newmazole before making further changes.

5. Potential Side Effects and Risks: While increasing the dosage of Newmazole can help control hyperthyroidism, it is also important to be aware of potential side effects, such as liver toxicity or agranulocytosis (a decrease in white blood cells). Regular blood tests will help monitor for these side effects.

6. Lifestyle Considerations: In addition to medication, managing hyperthyroidism may involve lifestyle changes, such as avoiding excessive iodine intake, managing stress, and maintaining a balanced diet. These factors can influence thyroid function and overall health.

In conclusion, the decision to increase your Newmazole dosage is based on the need to control your elevated thyroid hormone levels. It is essential to maintain open communication with your healthcare provider and to seek clarification on any concerns you may have regarding your treatment plan. Regular monitoring and adjustments will be key to managing your hyperthyroidism effectively. If you have further doubts, seeking a third opinion from an endocrinologist may provide additional reassurance and guidance.

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