Most thyroid nodules are harmless, but some can be cancerous. Scientists are still investigating the link between thyroid nodules and cancer. Some experts believe cancer might be more likely to occur within thyroid nodules than once thought.
In this article, we look at the symptoms, causes, and treatments of multinodular goiter, and their relationship with cancer.
Hoarseness and difficulty swallowing may be a symptom of a multinodular goiter.
Multinodular goiters do not always cause symptoms. A doctor will often diagnose multinodular goiters while conducting a physical exam or imaging study for another unrelated cause.
Sometimes a multinodular goiter will feel like a single nodule yet consist of several smaller ones.
A person may feel the nodules directly over their thyroid, which is located in the neck just below the Adam's apple in both men and women.
If a multinodular goiter grows large or presses against nearby structures, a person may notice the following symptoms:
- difficulty swallowing
- difficulty breathing when lying down
A person with a toxic multinodular goiter may have symptoms of hyperthyroidism. These include, but are not limited to:
- difficulty tolerating heat
- fast heart rate, even when at rest
- weight loss or inability to gain weight
- difficulty sleeping
One cause of multinodular goiter is an iodine deficiency, although this is rare in the United States. Iodine is a mineral present in small amounts in a person's diet.
The thyroid uses iodine to produce its hormones. Without enough iodine, the thyroid cannot perform its normal functions. For this reason, food manufacturers often add iodine to salt, called iodized salt, to reduce the prevalence of thyroid dysfunction.
Some people have greater risk factors for developing a multinodular goiter. Risk factors include:
- an iodine deficiency
- genetic factors that affect thyroid hormone production
- sex — women are more likely to develop nodules and thyroid disease
- age — older women are at higher risk of developing thyroid nodules
- a family history of multinodular goiter
- a history of an autoimmune thyroid condition, such as Hashimoto's thyroiditis or Graves' disease
If the thyroid gland is not making enough thyroid hormone, the pituitary gland in the brain will release more of the thyroid-stimulating hormone (TSH). The excess TSH can cause the thyroid to enlarge and create a multinodular goiter.
Likewise, an overactive thyroid that is making too much thyroid hormone can cause the thyroid to enlarge and become multinodular.
In some instances, a person may have no known cause for their multinodular goiter.
A physical examination may help to diagnose a multinodular goiter.
A doctor will begin to diagnose a multinodular goiter by taking a medical history.
They will ask about a person's previous health conditions, what medications they are taking, and whether there is a family or personal history of goiter or thyroid-related conditions.
A doctor will examine a person's neck and look for enlarged neck veins.
They can also feel the size and shape of the thyroid gland and look for anything unusual.
Blood tests can help to diagnose thyroid problems, especially tests for thyroid-stimulating hormone (TSH). If a person's TSH levels are low, it might mean that they have hyperthyroidism, which means that their thyroid is producing too much thyroid hormone.
If TSH levels are high, a person may have hypothyroidism (low thyroid hormone levels) because the body is trying to ramp up thyroid hormone production.
Follow up thyroid hormone tests to check for levels of hormones called T3 and T4 may be required to understand the complete picture.
A doctor may also perform thyroid imaging tests. These include a thyroid ultrasound. This test uses sound waves to recreate images of the thyroid, including the size and number of any nodules.
Sometimes, a doctor may recommend taking a biopsy of the thyroid nodules to test for the presence of cancerous cells.
A common biopsy method uses a small needle guided by an ultrasound, known as fine needle aspiration (FNA).
Doctors will probably recommend that anyone who has a nodule larger than 1 centimeter (cm) in size has a biopsy.
A thyroidectomy is rarely necessary.
Not all people with a multinodular goiter will require treatment. It often depends on thyroid function.
If the nodules are not producing thyroid hormone (non-toxic), a doctor will consider its size, symptoms, or growth pattern.
One treatment for both toxic and non-toxic goiters is radioiodine therapy.
The medication helps reduce the size of thyroid tissue. In the case of toxic goiters, it also shuts down abnormal thyroid hormone production.
The goiter typically shrinks 2 to 6 months after treatment, although it may take up to a year. Studies also have shown that in most cases, normal thyroid function continues or returns to normal after treatment.
Smaller goiters respond better to radioiodine therapy than large ones.
If the goiter and its nodules are relatively small in size, a doctor may recommend taking a thyroid hormone medication, such as levothyroxine (Synthroid).
However, research on this topic is not clear. Experts are divided between those who believe thyroid hormone helps this situation and those who do not.
This is the surgical removal of the thyroid gland. With advances in understanding thyroid disease, it is rarely necessary.
If the goiter is compressing nearby blood vessels, affecting a person's breathing, creating difficulty swallowing, or is causing psychological distress, a doctor may recommend removing the thyroid.
A doctor may also recommend thyroidectomy if a person is not a good candidate for radioiodine therapy. This is especially true if the multinodular goiter is extremely large, as large goiters do not respond as well to radioiodine therapy as smaller ones.
Relation to cancer
Studies have shown that between 10 to 20 percent of people with a multinodular goiter go on to develop thyroid cancer. Research has suggested that the risk of cancer in single and multinodular goiters is similar.
According to the Columbia University Department of Surgery, most people who develop cancer from a multinodular goiter have papillary thyroid cancer, which is the most common type of thyroid cancer.
A person may have a multinodular goiter without knowing about it, as it often creates no symptoms. Other people may have symptoms that impact their daily lives, such as difficulty swallowing or speaking.
Many treatment options are available for both toxic and non-toxic multinodular goiters. If a person suspects they may have a thyroid problem, they should talk to their doctor to find out the best course of action.