How much do you know about thyroid nodules?

Author: Zhang Aobo, attending physician, Beijing Friendship Hospital, Capital Medical University

Reviewer: Liu Liangfa, Chief Physician, Beijing Friendship Hospital, Capital Medical University

The thyroid gland is an important endocrine organ in the human body, located below the thyroid cartilage in the neck and on both sides of the trachea. The thyroid gland is shaped like a butterfly, like a shield, hence the name thyroid gland.

Figure 1 Original copyright image, no permission to reprint

As the incidence of thyroid tumors continues to increase worldwide, how to correctly understand thyroid nodules and rationally prevent, screen, diagnose and treat them has become a focus that everyone needs to pay attention to.

In March 2023, my country launched the second edition of the guidelines for the diagnosis and treatment of thyroid nodules and differentiated thyroid cancer. We now briefly explain the latest views of domestic experts.

1. What are thyroid nodules? What are their epidemiological characteristics?

Thyroid nodules are common diseases that refer to discrete lesions in the thyroid gland caused by abnormal, focal growth of thyroid cells. They are more common in women than in men.

There are usually no clinical symptoms of thyroid nodules in the early stages. As the nodules continue to grow, a visible or palpable mass may appear in the neck. Even when the nodules compress the tissues surrounding the thyroid gland, hoarseness, a feeling of pressure, difficulty breathing, and difficulty swallowing may occur.

The prevalence of thyroid nodules larger than 0.5 cm in diameter found by ultrasound in Chinese adults is 20.43%, of which 8%-16% are malignant tumors. The prevalence of thyroid nodules increases with age and body mass index (BMI).

Screening for thyroid nodules in the general population is not currently recommended unless there are high risk factors for thyroid cancer, including a history of head and neck radiation exposure during childhood, a history of whole-body radiation, a family history of thyroid cancer in a first-degree relative, and a family or personal history of genetic syndromes associated with thyroid cancer.

2. What are the commonly used examination methods for thyroid nodules?

For patients who have been found to have thyroid nodules or are suspected of having thyroid nodules, ultrasound examination is the preferred examination method.

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Ultrasound examination helps to distinguish benign from malignant thyroid nodules and predict their risk of malignancy. At present, the standard thyroid ultrasound examination report in my country uses the "Thyroid Imaging Reporting and Data System (TIRADS)" to grade thyroid nodules, with a total of 6 levels.

Thyroid nodules of grades 1-3 are usually benign. Grade 4 is divided into grades 4A, 4B and 4C, with malignant possibilities of 2%-10%, 10%-50% and 50%-90% respectively. Grade 5 means the possibility of malignancy is as high as over 90%, and grade 6 is a confirmed malignant nodule.

3. When does thyroid nodule need intervention? How to follow up?

Most benign thyroid nodules only require regular follow-up. Benign nodules that are asymptomatic and slow to grow do not require special treatment.

For thyroid nodules that are clinically suspected of being malignant (TIRADS grade 4A and above), fine needle aspiration biopsy (FNAB) can be performed to confirm the diagnosis. FNAB is usually performed by fine needle aspiration under ultrasound guidance to obtain the diseased cells of the thyroid nodule, and then sent to the pathology department for pathological diagnosis of the diseased cells. It is an accurate, economical and effective method for evaluating thyroid nodules, and the operation can be completed in the ultrasound examination room of the outpatient clinic.

Figure 3 Original copyright image, no permission to reprint

Thyroid nodules that have not undergone surgical treatment usually require reexamination every 6-12 months; for nodules that are benign based on ultrasound examination and/or FNAB, the follow-up interval can be appropriately extended; for nodules that are suspected of being malignant based on ultrasound examination and/or FNAB, the follow-up interval needs to be shortened.

4. What are the treatments for thyroid cancer? What is the prognosis?

Thyroid cancer is divided into different pathological types, among which papillary thyroid cancer is the most common, accounting for 85%-90% of all thyroid cancers.

Most papillary thyroid carcinomas have mild biological behaviors and a good prognosis. The overall 5-year survival rate of thyroid cancer in my country is approximately 84.3%.

The treatments for papillary thyroid carcinoma mainly include surgery, postoperative I131 treatment, and thyroid stimulating hormone (TSH) suppression therapy.

Surgical treatment is the most important, directly affecting subsequent treatment and follow-up and closely related to prognosis. Surgery includes the removal of the thyroid lobe and the clearance of the cervical lymph nodes. The specific scope of surgery needs to be determined based on the stage of the tumor, the patient's age, gender, the presence of high-risk factors, and the patient's wishes.

Whether I131 treatment is needed after surgery depends on the surgical procedure and the risk stratification of recurrence. Before I131 treatment, patients need to follow a low-iodine diet and stop taking levothyroxine sodium tablets for 2-4 weeks. Patients who undergo enhanced CT scans before total thyroidectomy should wait at least 1 month before I131 treatment.

TSH suppression therapy is adjusted through oral levothyroxine sodium tablets. The higher the oral dose of levothyroxine tablets, the lower the TSH value. The lower the TSH, the more beneficial it is to reduce the probability of postoperative recurrence. However, the higher the oral dose of levothyroxine, the more likely it is to develop hyperthyroidism, heat intolerance, sweating, palpitations, weight loss, fatigue and weakness. Long-term hyperthyroidism will have side effects on the heart and bones. Therefore, the dose of oral levothyroxine tablets needs to be adjusted according to the condition, and regular blood tests are required after surgery to monitor thyroid hormone levels and TSH suppression levels.

5. What precautions should be taken when taking oral levothyroxine tablets after thyroid surgery?

Levothyroxine tablets take effect 3-5 days after taking the medicine. It is taken orally once a day, and a stable blood concentration can be achieved after regular use for 4-5 weeks.

In order to maintain stable absorption and utilization of the drug, it is recommended to take it 30-60 minutes before breakfast. Try to avoid taking other drugs that affect the absorption of levothyroxine tablets, such as calcium carbonate, aluminum hydroxide, iron salts, etc., and the interval should be more than 4 hours.

During medication, try to avoid foods that may affect drug absorption, such as strong coffee, high-fiber foods, grapefruit, spinach, etc.

Since the half-life of levothyroxine tablets is 7 days, its effect is slow and long-lasting, and it is still relatively safe even if the drug is discontinued for a week. Patients who occasionally miss medication do not need to be overly nervous.

6. How to prevent the occurrence of thyroid nodules in daily life?

Reasonably control iodine intake. Prevent iodine overdose in high-iodine areas: Generally, in coastal areas, it is recommended to use iodine-free salt or reduce the intake of high-iodine foods, such as kelp, seaweed, marine fish, shrimp and other seafood, as well as salted eggs, pickles and other pickled products. Prevent iodine deficiency in low-iodine areas: Generally, inland areas, it is recommended to add iodized salt and increase iodine-rich foods, such as mushrooms, seaweed, pork liver, malt, etc. For patients who already have thyroid nodules, they should ensure an appropriate amount of iodine intake, which is conducive to controlling the further enlargement of thyroid nodules.

Stay away from radioactive environments. A history of exposure to radiation, especially in childhood, is a clear high-risk factor for thyroid tumors. In daily life, you should stay away from areas where you may be exposed to radiation. If you need to undergo a radiation-containing examination such as CT due to other medical conditions, you should cover your neck with a lead collar to reduce the amount of radiation received by the thyroid gland.

High sugar, high fat and obesity are prone to thyroid nodules, so you need to adjust your eating habits appropriately.

Negative emotions and excessive stress can harm thyroid health. Maintain a regular lifestyle, avoid staying up late, and keep your emotions stable and happy.