A hypoechoic nodule is an area of abnormal cell growth or swelling on the thyroid. Hypoechoic is how the nodule appears on an ultrasound like a dark gray mass rather than the surrounding tissue. This indicates that a nodule is a solid component rather than a liquid-filled one. A solid nodule is more likely to be cancerous than other nodules. However, a hypoechoic nodule may often be more benign than cancerous, even though the healthcare provider will offer additional testing to rule out cancer.

How Does an Ultrasound Work?

Ultrasound scans, also called sonography, use sound waves or echo instead of radiation to produce the images. So it is a very safe technique. These scans work by sending sound waves that penetrate the body by bouncing off muscles, tissues, bones, and other substances. A machine records these sound waves. The way the sound waves bounce back and form an image is called echogenicity, this image can be seen on a screen, and it is called a sonogram. The image obtained from ultrasound can be hypoechoic, hyperechoic, anechoic, or mixed.‌

Hypoechoic - It meansnot many echoes are reflected. These areas look dark gray in the image because they do not send back many sound waves. Hypoechoic are solid masses of dense tissue.
‌Hyperechoic - It means lots of echoes are reflected. These areas reflect a lot of sound waves, so they appear light gray in the images. These are not as dense as hypoechoic ones because they may contain fat, fluid, or air.
Anechoic - Anechoic means without any echoes. These areas look black on ultrasound images because they do not reflect any sound waves as it is often fluid-filled.

What Are the Causes of Hypoechoic Nodules in the Thyroid?

Thyroid nodules are widespread, and studies suggest that around 50 % of the population might have a thyroid nodule. Doctors do not know the exact causes of most thyroid nodules.

However, a few conditions can increase the risk of thyroid nodules development, including:

Deficiency of iodine.
Irregular cell growth on the thyroid.
Fluid-filled thyroid cysts.
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Less than five percent of hypoechoic thyroid nodules are cancerous. If the thyroid nodules are cancerous, it is caused by irregular cell growth. Medullary thyroid cancer is associated with a hereditary genetic mutation in about 25 percent of cases, so if any family members have had medullary thyroid cancer, there is a high risk of developing it.

What Are the Symptoms of a Hyperechoic Thyroid Nodule?

Thyroid nodules often show no symptoms. Most cases of thyroid nodules are detected during medical imaging for some other health concern. Some people identify thyroid nodules when they press on the larynx and the windpipe, making swallowing or breathing difficulties. When the thyroid nodule is large, it can lead to vocal changes or hoarseness. A thyroid nodule can sometimes be felt at the front of the throat. In a few other cases, a thyroid nodule will produce more thyroid hormones, causing abnormally high thyroid levels. This is called an active or toxic nodule, which can lead to hyperthyroidism.

The symptoms of hyperthyroidism include:

Weight loss.
Tremors.
Increase heartbeat.
Sweating.

Are Hyperechoic Thyroid Nodules Cancerous?

Most thyroid nodules are not cancerous and are referred to as benign. However, about five percent of these nodules can be cancerous. When the nodule is malignant, it can spread to other parts of the body and surrounding tissues. If the nodule of the thyroid is solid, there are more chances of being malignant than fluid-filled nodules. However, other features like the size of the nodule also indicate the risk of a nodule developing into thyroid cancer. Further testing will be recommended by the doctors if needed.

What Are the Other Tests Recommended After an Ultrasound?

The doctors will mostly do follow-up testing after an ultrasound image showing a hypoechoic thyroid nodule. Even though the risks of malignancy are low, the chance of cancer cannot be completely ruled off.

So they may recommend more tests that include:

1) Fine Needle Aspiration Biopsy -

Fine needle aspiration is a minimally invasive procedure. During a fine-needle aspiration biopsy, local anesthesia is given to the patient, and a needle takes cells from different parts of the thyroid nodules. Then they are examined under a microscope to check whether any cancerous cells are present. In most cases, a few different cell samples are collected to ensure cancerous cells are present in the nodule. There is no special preparation for this biopsy; most people do not require recovery time.

2) Blood Test -

A blood test helps measure the amount of thyroid-stimulating hormone in the blood that can help determine if the thyroid nodule is producing hormones or is active. If the blood test shows the nodule is producing hormones, it is not cancerous; it is due to hyperthyroidism.

3) Thyroid Scan -

During this scan, a radioactive iodine solution is injected into the area around the thyroid. Then the patient is asked to lie down while a specialized camera takes pictures. These images can also provide a better idea of thyroid function.

What Is the Treatment for Hypoechoic Thyroid Nodules?

The treatments used for hypoechoic thyroid nodules include:

1) Surgery - Surgery is the first-line treatment for thyroid cancer. If the thyroid nodule is cancerous, the healthcare provider will remove the nodule by removing the entire thyroid or part of the thyroid. Surgery is advised even in cases with a benign thyroid nodule if it interferes with the ability to speak, breathe, or swallow. The type of surgery will depend on whether the nodule is cancerous and the location. Three common types of thyroid surgery include:

Thyroidectomy - Removing the entire thyroid or just a part of the nodule.
Thyroid lobectomy - Removing the half of the thyroid (thyroid lobe).
Isthmusectomy - Removing the thyroid nodules.

2) Radioactive Iodine Therapy -

Radioactive iodine therapy kills the thyroid and cancerous cells, known as ablation. In some cases, radioactive iodine therapy treats thyroid cancer and thyroid diseases such as Grave’s disease.

3) Radiation -

In rare cases of thyroid cancer, the healthcare provider may advise radiation. This therapy kills cancer cells using radiation like radioactive iodine therapy. Radiation beams from outside the body are targeted toward cancer.

4) Chemotherapy -

Chemotherapy is not recommended in the treatment of thyroid cancer as it is not an effective treatment. However, in anaplastic thyroid cancer or follicular thyroid cancer, the doctors may recommend this with radiation therapy.

5) Targeted Drug Therapies -

If other treatments do not work to kill thyroid cancer, the doctors may recommend targeted drug therapies. These therapies interrupt the growth of cancer cells by blocking a protein called kinases that signal the growth of thyroid cells.

Conclusion

Hypoechoic thyroid nodules are very common and often benign. The exact cause of these nodules is unknown, and they usually do not present with any symptoms. However, if the nodule is large, it can interfere with speech, swallowing, and breathing. If a hypoechoic nodule is found during an ultrasound, doctors may advise additional testing to ensure it is not cancerous.