What is Thyroid Adenoma?
The thyroid is one of the biggest hormone-producing glands in our body, made of two connected parts, or lobes. It typically weighs between 20 to 30 grams in adults. It’s not uncommon to find thyroid lesions, or abnormal growths, in the gland, with about 4% to 7% of people having them. Most of these lesions don’t cause symptoms and the thyroid continues to function normally. The good news is that most thyroid lesions are not cancerous. Non-cancerous ones include cysts (fluid-filled sacs that can sometimes fill with blood), colloid nodules (benign growths filled with gel-like fluid), and thyroid adenomas.
Thyroid adenomas are benign, or non-cancerous, lesions of the thyroid. These lesions might or might not produce thyroid hormones. If they do produce hormones, they’re often called toxic thyroid adenomas. These adenomas typically don’t cause symptoms. However, when they become hazardous, or “toxic,” they can lead to hyperthyroidism, a condition where the thyroid is overactive. Most thyroid adenomas don’t cause symptoms and are usually discovered accidentally during a thyroid ultrasound. Less often, you might feel a noticeable lump in the thyroid, or see a growth on your neck.
What Causes Thyroid Adenoma?
Most of the time, growths in the thyroid (known as thyroid adenomas) happen by chance, and aren’t passed down through families. However, there are certain things in our surroundings and our genes that can increase the risk of having a thyroid adenoma.
For example, not getting enough iodine (an important mineral used by your body for a variety of processes) is a proven risk factor for these growths. In fact, it’s the most common reason people develop lumps in their thyroid worldwide, particularly in less developed countries.
On top of that, uncommon changes in certain genes, like BRAF, RET, KRAS, and a combination of PAX8-PPAR genes, are strongly linked to the development of thyroid adenomas.
Thanks to advances in technology, we’re now able to study these growths at a molecular level. This has helped us to tell the difference between benign (not harmful) and malignant (harmful) tumors.
Risk Factors and Frequency for Thyroid Adenoma
Thyroid adenomas are often found as single lumps in the thyroid and are more commonly seen in females. In two separate studies where autopsies were performed, thyroid adenomas showed up in 3% and 4.3% of cases. In the past, thyroid adenomas were more frequent, especially in areas where iodine was lacking (an issue known as endemic goiter). However, their occurrence has decreased in recent times, largely due to the introduction of salt enriched with iodine.
Signs and Symptoms of Thyroid Adenoma
Thyroid adenomas, or non-cancerous lumps in the thyroid gland, often go undetected until a thorough physical examination is conducted. Some people might notice a visible lump in their neck. In rare cases, they might experience difficulty breathing due to the lump pressing on their windpipe, hoarseness because of irritation of the nerve connected to the larynx, or difficulty swallowing due to esophagus compression. Most individuals with thyroid adenomas will not experience symptoms related to an overactive or underactive thyroid.
However, in some rare instances (about 1% of cases), if the adenoma causes hyperactivity of the thyroid, patients may experience a range of symptoms. In these cases, the symptoms might include:
- Weight loss
- Increased anxiety
- Heart palpitations
- Excessive sweating
- Changes in bowel habits
- Changes in hair or skin condition
- Menstrual irregularities in women who are still menstruating
It’s important for anyone experiencing these symptoms to seek medical consultation for potential thyroid issues.
Testing for Thyroid Adenoma
If you have a noticeable lump in your thyroid, a health professional will likely perform a number of steps to identify what it might be. The first test typically involves measuring the level of thyroid-stimulating hormone (TSH) in your blood. This helps to understand how well your thyroid is functioning. After this test, you’ll probably have an ultrasound scan of your thyroid, followed potentially by a fine needle aspiration biopsy. This is a procedure where a thin needle is used to remove a sample of cells from the lump for further analysis.
All patients with a noticeable lump in their thyroid should have their levels of thyroid hormones, specifically TSH and thyroxine, checked. If your TSH levels are low, this could indicate a “toxic adenoma” – a usually harmless lump in the thyroid that may affect its function. In this case, you might have an iodine-123 thyroid scan to help differentiate between a lump that’s producing too much hormone (a hyperfunctioning nodule or toxic adenoma) and one that’s not producing enough (a hypofunctioning nodule).
A lump that is producing too much thyroid hormone (hyperfunctioning nodule) is usually benign, or non-cancerous, with less than a 1% chance of being cancerous. On the other hand, a lump not producing enough hormone (hypofunctioning nodule) has a slightly higher chance, about 20%, of being cancerous. However, most patients with a thyroid lump have normal TSH levels, which is referred to as “euthyroid”.
The thyroid ultrasound will help determine whether the lump is a benign thyroid adenoma or possibly thyroid cancer. Some features of the ultrasound that can indicate a higher risk of the lump being cancerous include: reduced echoes (hypoechogenicity), small specks of calcium deposits (microcalcifications), irregular edges, absence of a halo sign, and increased blood flow inside the lump. Groups like the American Thyroid Association (ATA) and TIRADS use a scoring system, based on these ultrasound features, to evaluate the risk of the thyroid lump being cancerous.
If the thyroid lump has features that seem suspicious or if you’re considered at a high risk of thyroid cancer, a fine needle aspiration (FNA) might be performed. This procedure isn’t always conclusive. If the lump is a benign thyroid adenoma, the sample collected from the FNA will contain organized thyroid cells. But if the cells show abnormal structures and unusual features, known as atypia, it’s not clear what this means, and you might be described as having ‘atypia of undetermined significance’.
To definitely diagnose a benign thyroid adenoma, healthcare professionals need to rule out invasion into the capsule of the gland or blood vessels. This is usually done by a closer examination of the tissue, often after part or all of the thyroid has been removed surgically. Genetic testing is also becoming more important in predicting the risk of thyroid cancer, and results can influence the decision whether or not to proceed with surgically removing the lump.
Treatment Options for Thyroid Adenoma
Some people without symptoms but who have small growths on their thyroid (known as adenomas) that have been confirmed not to be cancerous, are typically monitored regularly with ultrasound scans. These scans involve using sound waves to create images of the inside of your body. Doctors might repeat a ‘fine needle aspiration’ – which is a procedure where a thin needle is used to remove a small sample of cells or fluid from the thyroid – if the growth gets bigger or if other worrying signs are seen on the ultrasound.
Advances in genetic testing have improved our ability to analyze the cells we gather from these biopsies. This means we can better determine whether surgery is necessary and, if so, how extensive it needs to be. In turn, this has reduced the number of unneeded surgeries and major operations to remove a person’s entire thyroid gland.
If you have a benign (non-cancerous) thyroid adenoma, a surgical procedure called a ‘thyroid lobectomy and isthmusectomy’ can be performed – this involves removing part of the thyroid gland. The same surgery can also be used for people with a certain type of thyroid cancer that is only minimally invasive. If the examination of the removed thyroid tissue shows no signs of cancer, then you usually won’t need further treatment, but will continue to monitor your thyroid hormone levels.
Patients with a solitary toxic nodule (a specific type of functioning thyroid adenoma) whose thyroid hormone levels aren’t within a normal range, may be treated with anti-thyroid drugs to restore normal thyroid function. Other treatment options include using radioactive iodine (known as iodine-131 therapy) or surgery (thyroidectomy). Advantages of surgical treatment include relief from any symptoms caused by the growth pressing on neighboring structures, an immediate improvement in overactive thyroid function (hyperthyroidism), and the avoidance of radioactive exposure to the healthy part of your thyroid. The use of injections of alcohol (ethanol) directly into the growth, in an attempt to shrink it, has been tried at certain specialized centers, but this approach is not common, and there are doubts about its long-term effectiveness.
What else can Thyroid Adenoma be?
Thyroid adenoma usually shows up as a single lump. Therefore, it needs to be distinguished from other conditions that can also cause lumps in the same area, like:
- A cyst that can occur in the parathyroid gland or in a part of the body known as the thyroglossal duct
- Multi-nodular goiter, which is a condition where multiple lumps develop on your thyroid
- Parathyroid adenoma, which is a benign tumor of the parathyroid glands
- Thyroiditis, an inflammation of the thyroid
- Carcinoma, which is a type of cancer that can originate in follicular cells, papillary cells, medullary cells, parathyroid cells, or any other type of cell
What to expect with Thyroid Adenoma
Thyroid adenomas, which are the most common non-cancerous lumps, typically have a very good prognosis, meaning patients usually recover well. But, there is about a 20% chance they could turn into cancer. When this happens, a team of various healthcare professionals comes together to manage the cancer treatment process.
Possible Complications When Diagnosed with Thyroid Adenoma
Most people who have thyroid adenomas don’t experience any symptoms. But, if the thyroid adenoma is functioning, it may result in signs of an overactive thyroid, which include symptoms like tiredness, excess sweating, trembling, heart palpitations, and anxiety. There can also be complaints of shortness of breath, a hoarse voice, and difficulty swallowing. These symptoms primarily occur when the thyroid tumor grows large enough to press on the windpipe or the esophagus.
Symptoms of Thyroid Adenoma:
- No Symptoms (most common)
- Tiredness
- Excess sweating
- Trembling
- Heart palpitations
- Anxiety
- Shortness of breath
- Hoarse voice
- Difficult swallowing
Preventing Thyroid Adenoma
Thanks to the common use of ultrasound scans, many people have been detected with unintentional thyroid nodules when being examined for different neck issues. It’s crucial to understand that most of these nodules are harmless growths and they are too tiny to feel by touch. The larger nodules, which are usually able to be felt, should undergo a procedure known as an ultrasound-guided fine needle aspiration (FNA). FNA is a method where a small, thin needle is passed through the skin and into the nodule to remove a sample for testing.
