What is TSH suppression therapy? What does it do?
TSH (thyrotropin, thyroid stimulating hormone), also known as “thyroid stimulating hormone,” is a hormone that is used in the treatment of thyroid cancer.
TSH (thyrotropin, thyroid stimulating hormone), also known as “thyroid stimulating hormone,” is a hormone secreted by our pituitary gland that promotes thyroid cell growth and hormone production. In patients with thyroid cancer, high TSH may accelerate the progression of the disease and increase the risk of recurrence.
The secretion of TSH is regulated by the level of thyroid hormones in the blood. When thyroid hormones are elevated, TSH is reduced; when thyroid hormones are reduced, TSH is elevated.
TSH suppression therapy takes advantage of this, where patients take oral thyroid hormone pills after surgery to suppress TSH at lower levels. Also called endocrine therapy.
Which patients are candidates for TSH suppression therapy?
Most patients with differentiated thyroid cancer (including papillary and follicular carcinomas), especially those at high risk of recurrence, need this therapy after surgery.
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But patients with medullary thyroid carcinoma and undifferentiated/lowly differentiated carcinoma, usually do not need it. This is because the growth of these two types of cancer is not dependent on the action of TSH.
Patients with medullary and undifferentiated carcinoma, however, should also take medication, as appropriate, after surgery, not to suppress TSH, but to replace the thyroid hormone that is missing after surgery. If a total thyroidectomy is performed, you need to take levothyroxine tablets for life after surgery; if only a single thyroid is removed, you generally need to take it for 3 months and then stop for 1 month after surgery, and then stop when thyroid function is normal on recheck.
How does TSH suppression therapy work?
The drug of choice for TSH suppression therapy is levothyroxine sodium tablets (L-T4), with trade names such as Eugenol or Raltez. These two drugs are chemically identical and there is no difference in efficacy.
It is important to note that there are different sizes of medications, and one tablet may be 50 micrograms or 100 micrograms. When you talk to your doctor, you need to tell him or her which size you are taking so you don’t get the wrong dose.
For more information on how to take thyroxine pills scientifically, click below:
How to review during treatment?
Many factors can affect the amount of thyroid hormone we need, such as weight, age, gender, season, and metabolic rate. In patients who have undergone unilateral thyroidectomy, the initial dose is usually 50 micrograms, after which it is dynamically adjusted by your doctor based on TSH levels. After the TSH “target” is reached, blood is drawn every 3 months for 1 year, every 3-6 months for 2 years, and every 6-12 months for 5 years to ensure that the TSH level is maintained within the target range.
The “target” level of TSH is determined by the physician, taking into account the surgical approach, postoperative follow-up time, risk of recurrence, and risk of side effects of treatment. When the risk of recurrence is high, the TSH needs to be reduced to a lower level; when the risk of recurrence is low, the requirements are less stringent.
What are the side effects of TSH suppression therapy?
Oral thyroid hormone pills are not fundamentally different from the thyroid hormone produced in our bodies, and when the medication is taken in the right amount, there are no side effects, even when taken for a long time.
However, if you take excessive amounts of thyroid hormone over a long period of time, especially if TSH is maintained at very low levels (less than 0.1 milliunits per liter) for a long time, it can lead to hyperthyroidism, which can aggravate your heart even if you don’t have symptoms. If you have pre-existing heart disease, arrhythmias, heart dysfunction and even angina and myocardial infarction may occur.
Postmenopausal women who take large doses of thyroxine may suffer from osteoporosis and even fractures. Oral calcium supplements and vitamin D can be taken under medical supervision.
Is TSH suppression therapy used alone, or in combination with other therapies?
There are many different types of thyroid cancer.
The primary and only promising route to cure for thyroid cancer is surgery, and TSH suppression therapy is important but usually used as an adjunct to surgery, and the vast majority of patients with differentiated thyroid cancer require TSH suppression therapy after surgery. It is unrealistic to expect to cure thyroid cancer with TSH suppression therapy alone.
Radioactive iodine-131 (I-131) therapy (RAI) is also an adjuvant therapy after surgery for differentiated thyroid cancer, but is needed in only some patients.
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TSH suppression therapy can be used in combination with RAI, but needs to be suspended for at least 2-3 weeks prior to RAI treatment and resumed after RAI treatment is completed. This is because only when the body has high TSH levels can the thyroid cells take up sufficient iodine for the purpose of radiotherapy.
Co-written by Dr. Naisi Huang, Cancer Hospital of Fudan University