Thyroid nodules: causes, tests, biopsy and follow-up explained

A lump in the neck can be alarming, and a thyroid nodule is one possible cause. Most nodules are harmless, but they should always be checked. This article explains what thyroid nodules are, how doctors investigate them and what happens next. It uses information from MedlinePlus, the US NIDDK, the NHS and the US National Cancer Institute.

1. Introduction

The thyroid is a small gland at the front of the neck that makes thyroid hormones ^[2]. MedlinePlus defines a thyroid nodule as a lump in the thyroid gland, caused by an overgrowth of thyroid cells ^[1]. There may be one nodule or several small ones. Some nodules are fluid-filled cysts, and some are non-cancerous growths ^[1].

MedlinePlus says nodules are very common, occur more often in women and become more likely with age. Only a few are due to thyroid cancer ^[1]. Some nodules make thyroid hormone and are called "hot", while others do not and are called "cold" ^[1].

2. Causes and risk factors

A cause is often not found ^[1]. MedlinePlus lists possible links to Hashimoto disease, an immune reaction against the thyroid, and to a lack of iodine in the diet ^[1].

Features that make cancer more likely, according to MedlinePlus, include a hard nodule, one that is fixed to nearby structures, a family history of thyroid cancer, a voice change, age under 20 or over 70, past radiation to the head or neck, and male sex ^[1]. The National Cancer Institute also lists radiation to the head or neck in childhood, a history of goitre (enlarged thyroid) and a family history of thyroid disease among risk factors for thyroid cancer ^[5].

3. Signs and symptoms

Most nodules cause no symptoms and are found by chance during a routine exam or a scan done for another reason ^[1]. Larger nodules may cause ^[1]:

• A visible swelling at the front of the neck
• Hoarseness or a change in voice
• Neck pain
• Trouble swallowing
• Breathing difficulty, especially when lying flat

A nodule that makes extra thyroid hormone can cause overactive thyroid symptoms: sweating, a fast pulse, nervousness, poor sleep, tremor, weight loss and more frequent bowel movements ^[1]. Nodules found alongside Hashimoto disease may come with underactive thyroid symptoms such as tiredness, constipation, dry skin and weight gain ^[1]. Older adults may have only vague symptoms such as tiredness or palpitations ^[1].

Not every neck lump comes from the thyroid. MedlinePlus notes that enlarged lymph nodes are the most common cause of neck lumps, and that most lumps in adults are not cancer ^[3].

4. Diagnosis and tests

MedlinePlus and the NIDDK describe these tests ^{[1, 2]}:

• Blood tests: thyroid-stimulating hormone (TSH) is usually checked first, along with other thyroid hormones. A high TSH usually suggests an underactive thyroid and a low TSH usually suggests an overactive one. Thyroid antibody tests may also be done to help diagnose immune conditions such as Hashimoto disease ^[2].
• Ultrasound: uses sound waves, takes about 30 minutes and is mainly used to look at nodules and help judge whether they are more likely to be cancerous ^[2].
• Thyroid scan: uses a small amount of radioactive iodine to show the size and shape of the gland and to find overactive nodules. You may be asked to avoid iodine-rich foods, such as kelp, for a week beforehand. It is not recommended in pregnancy or breastfeeding ^[2].
• Fine needle aspiration biopsy: a thin needle, usually guided by ultrasound, takes a tiny tissue sample that a laboratory checks to see whether the nodule is cancerous. It usually takes less than 30 minutes and the area may be numbed ^[2].

Sometimes genetic tests are done on the sample ^[1].

5. Treatment and follow-up

Treatment depends on the results and your doctor decides the plan. MedlinePlus explains ^[1]:

• Watchful follow-up: for a non-cancerous nodule that causes no symptoms and is not growing, the usual approach is regular physical exams and ultrasound. A repeat biopsy 6 to 12 months after diagnosis may be advised, especially if the nodule has grown.
• Surgery: removing all or part of the thyroid is recommended if the nodule is cancerous, causes swallowing or breathing problems, has an unclear biopsy result or makes too much hormone.
• Radioactive iodine: may be used for nodules that make too much hormone. It is not given to pregnant or breastfeeding women.

Surgery and radioactive iodine can cause a lasting underactive thyroid, which needs daily thyroid hormone medicine ^[1]. MedlinePlus says non-cancerous nodules are not life-threatening and many need no treatment beyond follow-up, and that the outlook for the most common thyroid cancers is very good after treatment ^[1].

6. Follow-up and radiation history

MedlinePlus advises people who have had radiation to the face or neck to contact their provider, because a neck ultrasound can check for nodules ^[1]. Follow-up exams and ultrasound are how doctors watch whether a harmless nodule changes ^[1].

7. When to see a doctor

MedlinePlus advises contacting a provider if you feel or see a lump in your neck, or have any symptoms of a nodule, and says all neck lumps should be checked promptly ^{[1, 3]}. The NHS advises a non-urgent GP visit for a new neck lump or one that is getting bigger, and for hoarseness, a sore throat or a cough lasting more than 3 weeks, or pain or pressure at the front of the neck ^[4]. Seek urgent help for difficulty swallowing or breathing ^[4].

In an emergency, call your local emergency number (112 in India, 911 in the United States).

8. Conclusion

Thyroid nodules are common and most are not cancer, but a new lump in the neck always needs a medical check. Blood tests, ultrasound and sometimes a biopsy show what the nodule is, and the follow-up plan is tailored to you by your doctor.