A goiter is an abnormal enlargement of the thyroid gland, the butterfly-shaped organ at the front of your neck that controls your metabolism. A healthy thyroid weighs between 10 and 20 grams and has a volume of roughly 7 to 10 milliliters on ultrasound. Anything larger than that qualifies as a goiter. Some goiters are barely noticeable, while others grow large enough to create visible swelling and interfere with swallowing or breathing.
What Your Thyroid Does and Why It Grows
Your thyroid absorbs iodine from your bloodstream and uses it to produce hormones that regulate your heart rate, body temperature, and how quickly you burn calories. A signaling loop keeps this system in balance: when thyroid hormone levels drop, your pituitary gland (a pea-sized structure at the base of your brain) releases more thyroid-stimulating hormone, or TSH. TSH tells the thyroid to work harder, both increasing hormone production and stimulating the growth of thyroid tissue.
A goiter forms when something disrupts this loop. If the thyroid can’t produce enough hormone, TSH stays elevated and the gland keeps growing. If the thyroid overproduces hormone, the gland may enlarge for a different reason entirely, such as inflammation or abnormal stimulation by the immune system. The enlargement itself isn’t a disease. It’s a physical response to an underlying problem.
The Most Common Causes
Iodine Deficiency
Worldwide, the most frequent cause of goiter is not getting enough iodine in your diet. When iodine intake is too low to support normal hormone production, thyroid hormone levels fall and the pituitary floods the thyroid with TSH. That sustained stimulation causes the thyroid’s cells to multiply and the gland to swell. This is largely a problem in regions without iodized salt. In the United States and other countries that fortify salt with iodine, deficiency-related goiters are uncommon.
Hashimoto’s Disease
Hashimoto’s disease is the leading cause of goiter in countries with adequate iodine intake. It’s an autoimmune condition in which the immune system produces antibodies that attack thyroid tissue. Large numbers of white blood cells accumulate in the gland, gradually destroying its ability to make hormones. As the thyroid struggles to keep up, TSH rises and the gland swells. You may notice fullness in the front of your throat, though the enlargement is usually painless. Over many years, sometimes decades, the ongoing damage can actually cause the thyroid to shrink and the goiter to disappear on its own.
Graves’ Disease
Graves’ disease is essentially the opposite problem. It’s also autoimmune, but instead of destroying the thyroid, the antibodies mimic TSH and overstimulate the gland. The thyroid enlarges and churns out excess hormone, leading to a fast heart rate, weight loss, anxiety, and heat intolerance. This type of enlargement is called a toxic goiter because the gland is both swollen and overproducing hormones.
Nodules and Multinodular Goiter
Sometimes the thyroid develops one or more lumps, called nodules. A single nodule can enlarge the gland (uninodular goiter), or multiple nodules can form throughout it (multinodular goiter). Most thyroid nodules are benign. They become more common with age and tend to grow slowly over years. Multinodular goiters can eventually produce excess thyroid hormone on their own, shifting from nontoxic to toxic.
Other Triggers
Certain medications can interfere with thyroid hormone production and promote gland enlargement. Lithium, commonly prescribed for bipolar disorder, is one well-known example. Pregnancy can also cause temporary thyroid swelling because of hormonal shifts and increased demand for thyroid hormone. Thyroid volume naturally varies somewhat by sex and body weight. Men tend to have slightly larger thyroids than women, and volume increases with age.
Toxic vs. Nontoxic Goiter
Doctors classify goiters partly by whether thyroid hormone levels are normal. A nontoxic goiter means the gland is enlarged but hormone levels remain in the normal range. You don’t have an overactive or underactive thyroid. Many goiters fall into this category, especially early on. A toxic goiter means the enlarged gland is producing too much thyroid hormone, causing symptoms of hyperthyroidism like rapid heartbeat, trembling hands, unexplained weight loss, and difficulty sleeping.
This distinction matters because it shapes treatment. A small nontoxic goiter that isn’t causing symptoms may need nothing more than periodic monitoring. A toxic goiter typically requires intervention to bring hormone levels under control.
What a Goiter Feels Like
Small goiters often cause no symptoms at all. You or your doctor might notice slight swelling at the base of your neck, but it doesn’t interfere with daily life. As a goiter grows, it can press on nearby structures. Common symptoms of a larger goiter include difficulty swallowing, a sense of tightness or fullness in the throat, hoarseness, coughing, and snoring. In more severe cases, the enlarged gland can partially obstruct your airway, making it harder to breathe during physical activity.
If the goiter is linked to an underactive thyroid, you may also experience fatigue, weight gain, dry skin, and sensitivity to cold. If it’s linked to an overactive thyroid, the symptoms tend to be the opposite: increased energy that tips into anxiety, weight loss, sweating, and a racing pulse.
How Goiters Are Diagnosed
Diagnosis usually starts with a physical exam. Your doctor feels the front of your neck while you swallow, checking for enlargement, tenderness, or lumps. A blood test measuring TSH and thyroid hormone levels reveals whether the gland is overactive, underactive, or functioning normally.
Ultrasound is the standard imaging tool. It measures the thyroid’s exact dimensions and volume, identifies nodules, and helps determine whether any lumps look suspicious enough to warrant a biopsy. During a biopsy, a thin needle extracts a small sample of cells for examination under a microscope. This is primarily done to rule out thyroid cancer, which accounts for a small minority of goiters but is important to catch early.
How Goiters Are Treated
Treatment depends on the goiter’s size, whether it’s causing symptoms, and what’s driving the enlargement.
- Observation: Small, nontoxic goiters that aren’t growing or causing discomfort often just need regular check-ups and periodic ultrasounds.
- Thyroid hormone replacement: If the goiter is caused by an underactive thyroid (as in Hashimoto’s disease), replacing the missing hormone can lower TSH levels and sometimes shrink the gland over time.
- Radioactive iodine therapy: For toxic goiters or Graves’ disease, radioactive iodine is taken as a single capsule or liquid dose. The thyroid absorbs it the same way it absorbs regular iodine, but the radiation destroys overactive thyroid cells. The gland shrinks and hormone levels drop over one to three months, with the full effect visible by three to six months. This usually results in permanent destruction of the thyroid, meaning you’ll need hormone replacement afterward.
- Surgery: Partial or complete removal of the thyroid (thyroidectomy) is an option when the goiter is very large, compressing the airway, or when cancer is suspected. After full removal, lifelong thyroid hormone replacement is necessary.
For iodine-deficiency goiters, simply increasing iodine intake through iodized salt, seafood, or dairy can halt further growth and sometimes reverse the enlargement, especially in younger people whose glands haven’t undergone long-term structural changes.