Conditions: Multinodular Goiter

A multinodular goiter is an enlarged thyroid gland containing multiple nodules, most of which are benign.

What is a multinodular goiter?

The thyroid is a butterfly-shaped gland in the front of the neck that makes hormones controlling the body's metabolism. A goiter simply means the thyroid gland has become enlarged. A multinodular goiter is an enlarged thyroid that contains multiple lumps, called nodules, of varying size, texture, and activity. The nodules can be solid, fluid-filled, or a mix of both.

Most of these nodules are benign (not cancer), and many people with a multinodular goiter feel completely well and have normal thyroid function.

How does a multinodular goiter develop?

A multinodular goiter usually develops slowly over many years. Several factors contribute:

• Iodine deficiency: iodine is the raw material the thyroid needs to make hormone. Worldwide, a lack of dietary iodine is the most common cause. When iodine is scarce, the gland works harder and enlarges to keep hormone levels normal.

• Growth-stimulating signals: the pituitary gland releases a messenger called TSH (thyroid-stimulating hormone) that tells the thyroid to grow and produce hormone. Long-term stimulation from TSH and other growth factors encourages thyroid cells to multiply.

• Genetics and family history: a tendency toward goiter and thyroid nodules often runs in families.

• Other contributors: smoking, certain foods (natural "goitrogens"), some medications, and environmental exposures can also play a role.

Over time, an initially smooth (diffusely enlarged) thyroid tends to become lumpy as different groups of cells grow at different rates, forming distinct nodules. Some nodules eventually begin to make thyroid hormone on their own, independent of the body's normal control.

How common is it, and who is affected?

Multinodular goiter is one of the most common thyroid conditions. It is:

• More common in women than in men (roughly four to five times more common).

• More common with increasing age.

• More common in regions where dietary iodine is low.

What is the difference between non-toxic and toxic multinodular goiter?

Multinodular goiters are grouped by how much thyroid hormone they produce:

• Non-toxic multinodular goiter: thyroid hormone levels remain normal (euthyroid). This is the more common form, and many people have no symptoms.

• Toxic multinodular goiter (Plummer disease): one or more nodules become overactive and produce too much thyroid hormone, causing hyperthyroidism (an overactive thyroid). This tends to develop later in life and can come on gradually.

What symptoms and problems can it cause?

Many people with a multinodular goiter, especially a small one, have few or no symptoms. When symptoms do occur, they usually result from the size of the gland or from overproduction of thyroid hormone.

From the size of the gland:

• Visible fullness or swelling in the lower front of the neck.

• A pressure or tightness sensation in the neck.

• Difficulty swallowing if the gland presses on the esophagus (the swallowing tube; see swallowing problems).

• Voice changes or hoarseness if the nerve to the voice box is affected (see voice).

• Breathing difficulty, cough, or noisy breathing if the windpipe is narrowed, sometimes more noticeable when lying flat.

• Substernal (retrosternal) goiter: sometimes the thyroid grows downward behind the breastbone into the chest. These can press on the windpipe and swallowing tube and are a more common reason for pressure symptoms.

Occasionally a nodule bleeds internally, causing sudden neck pain and temporary swelling on one side.

From an overactive thyroid (toxic goiter):

• Racing or irregular heartbeat, palpitations

• Unintended weight loss, increased appetite

• Feeling hot, sweating, tremor

• Anxiety, restlessness, trouble sleeping

How is a multinodular goiter evaluated?

Evaluation aims to determine the size and extent of the goiter, whether it is affecting thyroid hormone levels, and whether any nodule needs a closer look for cancer.

• Physical examination: the neck is felt to assess the size, texture, and number of nodules.

• Blood tests (thyroid function): a TSH level is the key first test to determine whether the thyroid is underactive, normal, or overactive. Additional hormone levels (such as free thyroxine) may be checked.

• Ultrasound: this painless imaging test maps the number, size, and characteristics of nodules. Certain features, such as being solid and dark-appearing, having irregular edges, tiny calcium specks, or being taller than wide, raise concern. A standardized scoring system called TI-RADS grades this level of concern to help decide which nodules need a biopsy.

• Fine needle aspiration (FNA): a very thin needle is used to take a small sample of cells from a nodule that is dominant, growing, or looks suspicious. Because there are many nodules, the sample is directed at the ones of greatest concern rather than at every nodule. Results are reported using the Bethesda system.

• Radioiodine uptake scan (thyroid scan): often used when the TSH is low. It shows which areas are overactive ("hot") and which are underactive ("cold"). Hot nodules are very rarely cancerous, while cold nodules may warrant further evaluation. A multinodular goiter characteristically shows a patchy mix of hot and cold areas.

• CT or MRI: these cross-sectional scans are helpful for large goiters or those extending into the chest, to show how far the gland reaches and whether it is compressing the windpipe or swallowing tube.

Is there a risk of cancer?

The large majority of multinodular goiters are benign. The risk that a clinically important cancer is present in an ordinary multinodular goiter is low. When cancer is found, it is most often a small papillary thyroid cancer, which tends to grow slowly and is usually very treatable.

The presence of multiple nodules does not mean higher cancer risk than a single nodule; the goal of evaluation is to identify the small number of nodules that need a biopsy. Goiters that extend into the chest can be harder to sample with a needle, which is one reason imaging and specialist assessment are important.

What happens over time?

A multinodular goiter usually changes slowly. Over years, the gland and individual nodules tend to enlarge gradually, and more nodules may form. Some nodules may increasingly make thyroid hormone on their own, so a non-toxic goiter can, over time, shift toward overactivity, first with subtle (subclinical) changes and eventually into a toxic goiter with symptoms of hyperthyroidism.

Management in brief

Management depends on symptoms, thyroid hormone levels, nodule features, and personal preference. Many people with a small, non-toxic goiter and normal thyroid tests are simply monitored over time with periodic examinations and ultrasound. Treatment is considered when the goiter causes pressure or breathing symptoms, produces too much hormone, or when a nodule is suspicious for cancer. Options may include radioactive iodine, medication, or surgery, which are described on the thyroid treatments page.