The thyroid gland is the largest endocrine organ in the front of the neck, attached to the trachea and limited to the breastbone, weighing 20-30 g. It consists of two symmetrical lobes, right and left. Each lobe is divided into lobules. Lobules are made up of follicles. Thyroid follicles are filled with follicular cells and a colloidal substance called thyroglobulin between them. The thyroid gland is one of the organs with the largest blood vessel network in the body.
Occasionally, lesions may occur in the thyroid gland. These lesions or abnormalities can arise from any tissue of the thyroid gland. Lesions of the thyroid gland can be grouped as benign or malignant. Thyroid adenomas are one of the benign lesions of the thyroid gland. Other benign lesions of the thyroid gland include cysts, thyroiditis, or colloid nodules. Thyroid adenomas can be confused with malignancies due to their mass appearance. Therefore, it is necessary to differentiate between malignancy and adenoma in a timely manner. However, the majority of thyroid adenomas do not show any symptoms and are detected incidentally. Thyroid adenomas are more common in women.
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Types of thyroid adenomas
Thyroid adenomas are encapsulated and homogeneous, solid tumors. There are two types of thyroid adenomas according to the part of the thyroid from which they originate:
- Thyroid follicular adenoma
- Fetal follicular adenoma
- Colloid type follicular adenoma
- Embryo-type follicular adenoma
- Hurthle cell type follicular adenoma
- Hyalinized trabecular type follicular adenoma
- Thyroid papillary adenoma
Thyroid adenomas may or may not be active, increasing thyroid hormones. According to this activity, thyroid adenomas can be divided into two types:
- Toxic (active) thyroid adenoma (functional thyroid adenoma)
- Non-toxic (inactive) thyroid adenoma (non-functional thyroid adenoma)
Environmental factors are cited as the cause for the majority of thyroid adenomas. One of them is iodine deficiency. Rarely, it can develop due to genetic mutations.
Patients with thyroid adenoma often have no signs of symptoms. However, in some patients, depending on the size of the adenoma, a mass sensation or a palpable mass may be seen in the neck. As the mass increases, shortness of breath, hoarseness and difficulty in swallowing may develop. These patients usually have normal levels of thyroid hormones. Rarely (1%) thyroid hormone excess and its symptoms can be seen.
Diagnosis of thyroid adenoma
When thyroid diseases are suspected, the first test is usually to look at the thyroid profile. The thyroid profile is TSH, T3 and T4 hormones. Thyroid ultrasonography, scintigraphy or fine needle aspiration biopsy can then be performed. It should be noted that sometimes even fine needle aspiration biopsy may not detect malignancies. When TSH is low in the thyroid profile, it is understood that the thyroid gland already secretes excess thyroid hormone without the need for TSH hormone. This raises the suspicion of toxic thyroid adenoma. These patients can be treated with radioactive iodine.
In thyroid adenomas, active and hyperfunctional, passive and hypofunctional thyroid nodules should be evaluated in terms of malignancy. While hyperfunctional nodules transform into malignancy at a rate of 1%, the risk of transformation of hypofunctional nodules into malignancy can be up to 20%. Therefore, signs of malignancy such as hypoechogenicity, microcalcifications, increased blood supply and irregular borders should be evaluated in thyroid ultrasonography.
The definitive diagnosis of thyroid adenoma is made by pathological examination of the piece taken after thyroid surgery.
Treatment of thyroid adenoma
Periodic ultrasonography or biopsy checks can be performed in patients with small or benign thyroid adenomas and no symptoms. In some patients, partial or more extensive surgery can be performed. Thyroid hormones should also be monitored regularly.
Functionally active thyroid adenomas can be treated with anti-thyroid drugs as they can disrupt thyroid hormones. In these patients, radioactive iodine or surgical treatment can also be performed. Surgical treatment is more advantageous for avoiding radiation exposure and for rapid recovery.
Although thyroid adenomas are benign tumors, they have a 20% chance of developing malignancy. Therefore, detailed evaluation and differential diagnosis are needed. In addition, close monitoring is required.