Toxic Adenoma - Causes, Types, Symptoms, Diagnosis, and Treatment

Creator: Dr. Asna Fatma
Published: 2023-07-10T11:11:21

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A toxic adenoma is a solitary thyroid nodule that causes hyperthyroidism. Read this article to learn more about thyroid gland disorder.

Written by

Dr. Asna Fatma

Medically reviewed by

Dr. Shaikh Sadaf

July 10, 2023

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Contents

What Is a Thyroid Gland?
What Is a Toxic Adenoma?
What Causes Toxic Adenoma?
What Are the Types of Toxic Adenomas?
How Common Is Toxic Adenoma?
How Are Toxic Adenomas Diagnosed?
What Is the Treatment of Toxic Adenoma?
What Are the Possible Complications of Toxic Adenoma?

Introduction:

Toxic adenomas are solitary lumps growing in the thyroid gland that leads to excessive thyroid hormone production or hyperthyroidism. Sometimes, there are multiple nodules causing similar symptoms; in this case, the condition is known as toxic multinodular goiter. Toxic adenoma occurs primarily due to iodine deficiency in developing countries. Women and elderly people have a higher risk of developing toxic adenomas. The symptoms of the condition are mostly due to hyperthyroidism resulting from toxic adenomas.

What Is a Thyroid Gland?

The thyroid is a small, vascular, butterfly-shaped gland present in front of the neck responsible for the synthesis and secretion of thyroid hormones. These hormones are responsible for growth, development, metabolism, and several other vital functions of the body. An underactive thyroid gland leads to a condition known as hypothyroidism, whereas an overactive thyroid leads to a condition known as hyperthyroidism.

What Is a Toxic Adenoma?

Thyroid adenomas are benign (non-cancerous) thyroid gland lesions, often occurring in solitary. These lesions may be active or inactive in nature. Active thyroid adenomas produce excess thyroid hormones known as toxic, whereas inactive adenomas do not produce thyroid hormones. The body can not manage this excess thyroid hormone produced by the toxic adenomas; therefore, it often leads to hyperthyroidism (overactive thyroid). Toxic adenoma occurs when a single nodule or lump gets enlarged. Moreover, if there are multiple thyroid nodules, the condition is referred to as multinodular goiter (swelling in front of the neck occurring due to an increase in the size of the thyroid gland). Toxic adenomas function autonomously, which means they do not require thyroid-stimulating hormones produced by the pituitary gland to produce thyroid hormones.

What Causes Toxic Adenoma?

A toxic adenoma may occur sporadically, meaning it can appear randomly without any evident cause. However, several environmental and genetic factors may lead to the development of toxic adenoma.
The most common cause of toxic adenoma in developing countries is iodine deficiency. The thyroid gland requires iodine to produce thyroid hormones thyroxine (T4), triiodothyronine (T3), and calcitonin. A deficiency of iodine in the diet leads to the inability of the thyroid gland to produce thyroid hormones. This leads to low levels of thyroid hormones in the body, which results in growth in the thyroid gland size to compensate for this deficiency. The thyroid gland tries to absorb as much iodine available in the diet as possible. In order to do this, the thyroid gland enlarges in size.
Genetic mutations and genetic rearrangement of certain genes.
Thyroid cysts (fluid-filled cavities in the thyroid gland) may also cause toxic adenoma.
Hashimoto’s disease (an autoimmune condition affecting the thyroid gland) may also cause chronic inflammation of the thyroid gland and subsequent enlargement of thyroid nodules.
Thyroid cancer may also be a reason for the development of toxic adenoma. However, the chances of a nodule becoming cancerous is very rare.

What Are the Types of Toxic Adenomas?

Toxic adenomas are solitary and homogenous tumors that are classified into two types:

Follicular: More commonly occurring type of toxic adenoma, which is further classified based on its functioning as hot, warm, or cold.
Papillary: Rarely occurring form of toxic adenomas.

The toxic follicular adenomas are further classified into the following types depending on their cellular structure:

Fetal adenoma.
Colloidal adenoma.
Embryonal adenoma.
Hurther cell adenoma.
Hyalinizing trabecular adenoma.

How Common Is Toxic Adenoma?

Toxic adenoma occurs as a single thyroid nodule.
These are more common in females as compared to males.
The incidence of toxic adenoma is about 3 % to 5 % in patients diagnosed with hyperthyroidism.
A toxic adenoma is more prevalent in elderly patients and developing countries with an iodine deficit diet.

What Are the Symptoms of Toxic Adenoma?

The symptoms of toxic adenoma are similar to hyperthyroidism because of the associated hyperthyroidism that occurs from the condition. The common symptoms of toxic adenoma are:

Unusual weight loss.
Increased appetite.
Diarrhea.
Fatigue.
Irritability.
Sleeping problems.
Tremors and shaking.
Palpitations.
Excessive sweating.
Feeling excessively hot.
Rapid or increased heartbeat.
Muscle weakness.

How Are Toxic Adenomas Diagnosed?

The diagnosis of toxic adenoma is made in the following ways:

Blood tests are done to check for the levels of thyroid hormones. In the case of toxic adenoma, the levels of thyroid hormones are elevated.
Thyroid antibody tests are done to check for the presence of Grave’s disease. In the case of nodular disease, the thyroid antibody test is negative.
An ultrasound of the neck should be done to assess the size, location, and extension of the thyroid nodule.
CT scans (computed tomography) and MRI (magnetic resonance imaging) are done to study the anatomical and structural details of the goiter and thyroid nodules.
Fine Needle Aspiration Cytology is a biopsy done with the help of the fine needle aspiration method. In this test, multiple tissue samples are collected and tested for the presence of any malignancy in the nodules.
A thyroid iodine uptake test is also performed to evaluate how much iodine is being used by the thyroid gland. This test confirms an overactive thyroid gland.

What Is the Treatment of Toxic Adenoma?

The treatment modalities of toxic adenoma include:

Surgery: Surgical removal of the toxic adenoma is done. Moreover, total or near-total thyroidectomy may be done depending on the severity of the disease. The patient will have post-surgical hypothyroidism.
Radio Active Iodine: Radioiodine is the definitive and most efficient treatment option for toxic adenoma. The patient is given a dose of radioiodine in the form of oral capsules or liquid. Radioiodine gets concentrated in the thyroid gland and causes slow destruction of the gland. This iodine does not have any harmful effects on other parts of the body.
Anti-thyroid Drugs: Anti-thyroid drugs like Propylthiouracil, Carbimazole, and Methimazole are commonly used to treat hyperthyroidism while waiting for radioactive iodine ablation and before surgery (to prepare for the surgery).

What Are the Possible Complications of Toxic Adenoma?

The possible complications of toxic adenoma are:

Problems in swallowing and breathing may occur if the size of the adenoma is extremely large.
If left untreated, hyperthyroidism due to toxic adenoma may progress into thyrotoxicosis (excessive thyroid hormone).
Thyrotoxicosis may increase the risk of atrial fibrillation (irregular and rapid heart rhythm), heart failure, and decreased bone density.
Post thyroidectomy (surgical removal of the thyroid gland), the patient will suffer from hypothyroidism.

Conclusion:

A toxic adenoma is a rare thyroid gland disorder with an excellent prognosis. The diagnosis and treatment of the condition are definitive and effective. Moreover, about 45 % to 75 % of the patients remain euthyroid (state of having normal thyroid gland function) after their treatment. However, in rare cases, the toxic adenoma may become cancerous.

Frequently Asked Questions

1. Is Toxic Adenoma Associated With Hyperthyroidism or Hypothyroidism?

Solitary, toxic adenomas manifest as benign nodules that may exhibit activity or remain inactive. Linked with hyperthyroidism, these adenomas involve an overactive thyroid gland that generates surplus thyroid hormones, leading to symptoms like weight loss, fatigue, irritability, palpitations, and muscle weakness.

2. Can Hyperthyroidism Result From Thyroid Adenoma?

Certainly, hyperthyroidism can be induced by a thyroid adenoma. This noncancerous growth, or nodule, materializes within the thyroid gland. The thyroid adenoma prompts an overproduction of thyroid hormones, specifically T4 (thyroxine) and T3 (triiodothyronine).

3. Which Tumor Leads to Hyperthyroidism?

Among the prevalent tumors, a benign variant named toxic adenoma or thyroid nodules holds the spotlight. These lumps materialize within the thyroid gland, exhibiting potential activity or remaining inactive. When active, they stimulate heightened production of thyroid hormones, resulting in the manifestation of hyperthyroidism.

4. How Can One Determine if Hyperthyroidism Is Cancerous?

Determining if hyperthyroidism is caused by cancer necessitates a multifaceted approach involving medical assessments and diagnostic procedures. While many thyroid cancers exhibit no symptoms, some may manifest with signs like pain, swallowing difficulties, and alterations in voice. Blood tests for thyroid hormone assessment, alongside imaging studies such as radioactive iodine uptake (RAIU) scans, aid in pinpointing areas of overactivity. Ultrasounds play a role in the diagnostic process, and a biopsy is a valuable tool for identifying cancerous tissues.

5. Does Pituitary Adenoma Contribute to Hypothyroidism?

Indeed, the presence of a pituitary adenoma can play a role in the development of hypothyroidism. The pituitary gland assumes a pivotal role in orchestrating the activity of the thyroid gland by releasing thyroid-stimulating hormone (TSH), which, in turn, prompts the release of thyroid hormones. However, in instances of pituitary adenoma, this harmonious regulation can be disrupted, leading to an impairment of normal thyroid function and, consequently, the onset of secondary hypothyroidism.

6. What Is the Most Effective Treatment for a Toxic Thyroid Nodule?

Surgery emerges as the foremost and highly efficacious treatment for a toxic thyroid nodule, with the extent ranging from total to near-total thyroidectomy, depending on the severity of the condition. Alternatively, treatment avenues encompass the administration of radioactive iodine in either liquid or oral form, inducing a gradual gland deterioration. The management toolkit also encompasses anti-thyroid drugs such as Methimazole and Propylthiouracil, offering additional avenues for effective intervention.

7. Do Toxic Nodules Eventually Resolve on Their Own?

Inactive, hyperfunctioning, and diminutive nodules often resolve spontaneously without intervention. However, the resolution of such nodules can vary from person to person. Nonetheless, consistent follow-up is imperative for monitoring progress. In instances where nodules show an increase, the management options encompass surgery, radioactive therapy, or the utilization of anti-thyroid drugs.

8. What Methods Are Used to Diagnose a Toxic Nodule?

Diagnosing a toxic nodule involves various methods, starting with a physical examination incorporating palpation to discern the presence of single or multiple nodules. Blood tests are instrumental in assessing thyroid function, while a thyroid scan utilizing radioactive iodine aids in gauging the activity of the nodules. Ultrasound imaging offers a detailed visualization of the nodules. Fine needle aspiration biopsy may also be employed to evaluate further and diagnose toxic nodules.

9. What Diagnostic Test Is Employed for Thyroid Adenoma?

Evaluating thyroid adenoma involves a battery of diagnostic tests such as assessing TS levels, conducting ultrasound examinations of the gland, and employing Fine Needle Aspiration (FNA) when there's a heightened risk of malignancy. Additional diagnostic measures encompass thyroid ultrasound scans and radioactive iodine uptake scans, contributing to the comprehensive diagnosis of thyroid adenoma.

10. What Is the Pathological Nature of Toxic Adenoma?

Within the thyroid gland, thyroid adenomas manifest as a distinct type of tumor. Characteristically uniform in appearance, these tumors commonly present as solitary lumps encased in a protective covering. When scrutinized under a microscope, thyroid adenomas are typically classified as either follicular or papillary based on specific characteristics. The more prevalent follicular type contrasts with the rarity of papillary adenomas. Signs such as invasion of the protective capsule and blood vessel infiltration are strong indicators of malignancy in these adenomas.

11. What Laboratory Findings Are Associated With Toxic Adenoma?

Elevated thyroid levels result from the hyperfunctioning adenoma, resulting in decreased TSH levels. When subjected to the Radioactive Iodine Uptake (RAIU) Test, there is an observable increase in iodine uptake, accompanied by elevated calcitonin levels. It's worth noting that thyroid antibodies typically remain within normal ranges and are not usually elevated in this scenario.

12. Can a Toxic Adenoma Be Malignant?

Hyperfunctioning thyroid nodules, known as toxic adenomas, operate independently to overproduce thyroid hormones and are typically deemed benign, indicating a non-cancerous nature. However, it is important to acknowledge that there is a slight risk of malignancy in certain instances. To definitively confirm malignancy, a biopsy, such as a fine needle aspiration (FNA) biopsy, is often employed for a thorough and accurate diagnosis.

13. Is Toxic Adenoma Characterized as Benign or Malignant?

Benign by nature, toxic adenomas are typically noncancerous entities. Despite their non-malignant classification, these conditions exhibit an abnormality in releasing excessive thyroid hormones, resulting in hyperthyroidism. It is noteworthy, albeit rare, that there may be a minimal risk of malignancy associated with toxic adenomas in certain instances. In such rare cases, a biopsy emerges as a valuable diagnostic tool to ascertain the presence of malignancy.

14. Is Toxic Thyroid Adenoma Synonymous With Follicular Adenoma?

Distinct from a follicular adenoma, a toxic thyroid adenoma is not interchangeable. The former is characterized by its cellular architecture, often stumbled upon incidentally due to its size, and notably does not induce an excess production of thyroid hormones. On the contrary, a toxic thyroid adenoma triggers hyperthyroidism through the overproduction of thyroid hormones. The dissimilarity lies in their respective impacts on thyroid hormone levels and their distinctive cellular features.

Sources

Dr. Shaikh Sadaf

Endocrinology

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