By doing the appropriate tests as recommended by the doctor, the doctor can more accurately assess the condition and develop a treatment plan.
Patients with thyroid nodules or suspected thyroid cancer may be recommended to have blood work done. What are the indicators that are included in the “thyroid work”? How should patients with thyroid cancer understand what these indicators mean?
What indicators are included in “A 7” and “A 5”?
What indicators are included in “A 7” and “A 5”?
The 5 tests are the most basic tests of thyroid function and include thyroid hormones (T3, T4, FT3, FT4) and thyroid stimulating hormone (TSH). If you are simply testing thyroid function, these 5 items are sufficient.
The 7 thyroid tests, which add the thyroid autoimmune antibodies TPOAb (thyroid peroxidase autoantibodies) and TGAb (thyroglobulin autoantibodies) to the 5 thyroid tests, can aid in the diagnosis of autoimmune thyroiditis such as Hashimoto’s thyroiditis.
Thyroglobulin (Tg) and calcitonin (CT) are often added as an adjunct to the diagnosis of thyroid tumor conditions.
TRAb (thyrotropin receptor antibodies), a thyroid autoimmune antibody, is usually ordered only after the detection of hyperthyroidism (“hyperthyroidism”) for definitive diagnosis and staging, and is not used as a routine thyroid function test.
It is important to note that calcitonin can help diagnose medullary thyroid cancer; the rest of the thyroid function indicators do not help diagnose thyroid cancer.
The following is a description of each of these indicators.
Thyroid hormone
What indicators are included in thyroid hormones?
Broadly defined, thyroid hormones include triiodothyronine (T3), thyroxine (T4), free T3 (FT3), and free thyroxine (FT4). They reflect the function of the thyroid gland.
What do thyroid hormone indicators say?
Simply, elevated indicators mean that there is too much thyroid hormone in the body, suggesting “hyperthyroidism,” while decreased indicators mean that there is not enough thyroid hormone, suggesting hypothyroidism (“hypothyroidism”). T3 and T4 are less sensitive than FT3 and FT4, and are no longer commonly used in some hospitals. At my center, FT3 and FT4 reference values range from 2.63 to 5.7 and 9.01 to 19.05 picomoles per liter (pmol/L), respectively.
Of course, there are more precise clinical criteria for diagnosing “hyperthyroidism” and “hypothyroidism,” and they have many different causes and different treatment modalities. The most important thing is to make sure that you have a good understanding of the situation.
Remind you that there is no correlation between thyroid hormones and thyroid cancer, and if these 4 indicators are abnormal, they are not usually indicative of thyroid cancer, so you don’t need to worry too much.
Thyroid stimulating hormone (TSH)
What does TSH indicate?
TSH is a hormone that regulates thyroid function. When thyroid hormone decreases, the body boosts thyroid secretion by increasing TSH production.
Thus, it suggests the opposite of thyroid hormone: an increase in TSH suggests not enough thyroid hormone (“hypothyroidism”), while a decrease suggests too much thyroid hormone (“hyperthyroidism”).
TSH is more sensitive than T3 and T4 in reflecting thyroid function. It can signal to us early in the process of abnormal thyroid function. For example, an elevated TSH with normal T3 and T4 without any clinical symptoms is called “subclinical hypothyroidism,” suggesting that thyroid function has begun to decline. Depending on the level of TSH elevation, some patients may need to take medication.
- What does TSH indicate in patients with thyroid cancer?
What does TSH indicate in patients with thyroid cancer?
In patients with thyroid cancer, TSH screening has additional implications.
Studies suggest that TSH has a role in promoting thyroid tumor development, so thyroid hormone therapy is routinely taken after thyroid cancer surgery, both to supplement thyroid hormones and to suppress TSH. therefore, for patients with postoperative thyroid cancer, the indicator that is of most interest to physicians is TSH, and medications are adjusted based on TSH values.
At this point, the range of control of TSH is different from normal. Do not worry about a lower-than-normal TSH after taking the medication, because that is what your doctor wants. There is still some debate as to what the postoperative TSH should be, and the general consensus is that control below 1 milligram per liter (mIU/L) is satisfactory.
Thyroid autoimmune antibodies (TPOAb, TGAb)
The normal immune response is an important protection against the outside world, but sometimes the immune system makes a mistake and “beats itself up”, which is when autoimmune disease occurs, and autoimmune antibodies can be found in blood tests.
The routine clinical screening tests for thyroid autoimmune antibodies include TPOAb and TgAb, which are needed whether you suspect thyroid cancer or not. If the values are outside the normal range, it is important to ask your doctor for judgment and management.
Tumor markers (Tg, CT)
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Thyroglobulin (Tg): can be used to monitor tumor recurrence after total thyroidectomy
Tg originates from thyroid tissue and may be elevated by inflammation, benign, or malignant tumors, so it is not generally used as a tumor marker to diagnose thyroid cancer.
But when patients with papillary and follicular thyroid cancer have elevated Tg after total thyroidectomy, it is more likely to be due to tumor tissue release, suggesting postoperative residual, recurrent, or metastatic disease. Therefore, after total thyroidectomy, follow-up review of Tg can be an important tool to detect tumor recurrence.
Calcitonin (CT): can be used for screening and postoperative follow-up of medullary thyroid cancer
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Elevated calcitonin is often strongly associated with medullary thyroid cancer and is therefore used to screen for medullary cancer in patients with thyroid nodules. It is not easily “misdiagnosed” or “missed” and is highly accurate.
Postoperative calcitonin testing can also be used for follow-up of medullary carcinoma, and persistent elevations are often indicative of postoperative residual, recurrent, or metastatic disease.
Summary
A complete thyroid function test should include 7 items: T3/FT3, T4/FT4, TSH, TPOAb, TGAb, Tg, and CT. It is important to check all 7 of these items when a thyroid nodule is found, including in patients with suspected thyroid cancer, for preoperative clarification of the combination of hyperthyroidism, Hashimoto’s thyroiditis, and whether it is a medullary carcinoma.
If it is a review, you need to follow your doctor’s advice to get the appropriate tests so that you can more accurately assess your condition and develop a treatment plan.
Co-written by Dr. Yiming Cao, Cancer Hospital of Fudan University