Guide To The Causes, Risk Factors, And Complications Of Thyroid Nodules
Thyroid nodules are lumps or growths in an individual's thyroid gland above their breastbone and at the base of their neck. The majority of thyroid nodules do not produce symptoms or cause any issues. However, some nodules can make it hard for a patient to swallow correctly, breathe well, and produce a healthy amount of thyroid hormone called thyroxine. Thyroid nodules that produce excess hormones can result in symptoms such as unexplained weight loss, tremor, rapid heartbeat, increased sweating, and nervousness. Thyroid nodules can be identified through the use of a physical examination, thyroid function tests, thyroid scans, ultrasonography, and fine-needle aspiration. Thyroid nodule treatment is dependent upon the type of nodules and the symptoms they produce, though common methods include thyroid hormone suppression therapy, surgery, radioactive iodine, anti-thyroid medications, and alcohol ablation.
Thyroiditis
An individual's pre-existing thyroiditis can cause them to be at a higher risk of developing nodules in their thyroid gland than those not affected by thyroiditis. A form of thyroiditis called Hashimoto's thyroiditis has proven to have a strong association with the development of nodules in a patient's thyroid gland. Hashimoto's thyroiditis is the most prevalent cause of hypothyroidism in the general population. Thyroiditis or inflammation that occurs in the thyroid causes damage to the cells that make up the gland. The body responds and heals the damaged tissues in the thyroid. In some cases, an individual's body will produce an overgrowth of new thyroid tissue cells by mistake during this healing process. This overgrowth of thyroid tissue is referred to as a thyroid nodule. Thyroid nodules are more likely to develop in women who have a pre-existing condition that affects the thyroid gland than they are to develop in men affected by a pre-existing thyroid condition.
Iodine Deficiency
An individual's thyroid gland located in their neck is responsible for producing numerous hormones that help with the regulation and function of organs and processes around the body. Iodine is an element the thyroid gland requires to produce thyroid hormones. Iodine is only provided to the body through the food an individual consumes, as the body is not able to produce this element on its own. Deficient levels of iodine activate an adaptive process in the gland where it induces the release of thyroid-stimulating hormone. This increased secretion of thyroid-stimulating hormone has a direct effect on the tissues of an individual's thyroid gland. This effect leads to an increase in the thyroid gland mass and the number of normal cells in the thyroid tissues. This response is meant to help the gland better absorb iodine. The excess thyroid tissues can develop into thyroid nodules and other abnormalities. Individuals who develop thyroid nodules due to an iodine deficiency are at a higher risk of developing malignancy in their thyroid tissues.
Thyroid Tissue Overgrowth
The cause of thyroid nodules can be due to thyroid tissue overgrowth or adenomatous hyperplasia. Nodules in the thyroid gland often contain fluids because of a process called cystic degeneration. The overgrowth of thyroid cells can produce bleeding from the fragile blood vessels that congregate in the thyroid tumors. Sometimes the overgrowth of the thyroid tissues can lead to an overproduction of thyroid hormone because the autonomous or hyperfunctioning thyroid nodules inappropriately produce hormones. This inappropriate production of thyroid hormone produces symptoms of hyperthyroidism, including muscle weakness, intolerance of heat, irritability, high heart rate, anxiety, and weight loss. Another mechanism where thyroid tissue overgrowth can cause the development of thyroid nodules is when increased levels of TSH in the blood cause the thyroid gland to produce more healthy thyroid tissue to help collect iodine. The increased amount of tissue produced by this process is considered to be an overgrowth of thyroid tissue resulting from a compensatory mechanism of the thyroid gland.
Family History Of Thyroid Nodules
An individual who has a family history of thyroid nodules is at a greater risk of developing these growths than someone who does not have a family history. Several disorders passed from one individual to another through DNA can cause the development of thyroid nodules. Multiple endocrine neoplasia syndromes are a group of endocrine system disorders that cause the abnormal development of several tissue growths or tumors in one or more glands around the body. Mutations in the part of an individual's DNA that occur in the MEN1, RET, and CDKN1B genes are responsible for causing multiple endocrine neoplasia syndromes. Familial papillary thyroid carcinoma that runs in a patient's family can cause them to be at an increased risk of developing thyroid nodules that may or may not progress into malignant carcinomas. Individuals who have a family history of multinodular goiter are more likely to develop nodules and overgrowth in their thyroid gland than individuals with no family history of the condition.
Thyroid Cyst
An individual's thyroid nodules may exhibit cystic characteristics or may develop as a result of the presence of fluid-filled cysts in their thyroid gland. A non-cancerous growth only filled with fluid that forms in the thyroid gland is referred to as a thyroid cyst. A growth filled with both fluid and solid components that develops in an affected individual's thyroid gland is referred to as a complex thyroid nodule. The excess growth of thyroid tissue that has contributed to the development of an individual's existing cysts in their thyroid gland can also contribute to the production of solid thyroid nodules. Nodules in an individual's thyroid gland composed exclusively of fluid-filled cysts will typically present as benign and will remain benign. However, complex thyroid nodules composed of at least fifty percent solid components but also contain cysts are at the same increased risk of carcinogenesis as completely solid thyroid nodules.
Multinodular Goiter
An individual affected by thyroid nodules may experience a multinodular goiter as a complication of their thyroid abnormalities. Multinodular goiter is an enlarged thyroid gland that contains multiple thyroid nodules. The nodules that form a multinodular goiter may be small or large, and may or may not be malignant. A multinodular goiter can contain multiple solid nodules, multiple fluid-filled nodules, or a combination of both types of thyroid nodules. Individuals who develop a multinodular goiter due to an initial thyroid nodule may experience symptoms like the feeling of an object being stuck in the throat and one or more palpable lumps on the front of the neck. Individuals who have known thyroid nodules should undergo periodic screening to ensure if they develop a multinodular goiter, it is not precancerous and does not progress into a malignancy. Individuals who experience complications with the normal function of the windpipe, throat, and or esophagus may need to have surgery to remove the thyroid or reduce the size of the gland. A multinodular goiter also often means an affected individual has too much TSH in their blood promoting the growth of thyroid tissue. Medication to supply thyroid hormone is given to help reduce TSH levels.
Hypothyroidism
An individual who has hypothyroidism may develop nodules in their thyroid gland as a complication of their thyroid condition. The most common cause of hypothyroidism that results in the development of thyroid nodules is Hashimoto's thyroiditis. Hashimoto's thyroiditis occurs when the individual's immune system inappropriately attacks the tissues of the thyroid gland, causing them to become damaged. The individual's body responds to this tissue damage by implicating its repair and healing processes. During this process of repairing damage to the thyroid tissue, mistakes and errors may occur in the reconstruction of cellular DNA. Errors in the DNA of thyroid cells may cause them to grow further and divide more often. This malfunction does not always cause cancerous growth of the affected tissue, but benign growths of healthy thyroid tissue referred to as adenomas or thyroid nodules. Individuals who are deficient in iodine, which is required for the thyroid to produce thyroid hormone, may develop hypothyroidism. This type of hypothyroidism can produce thyroid nodules when levels of TSH in the blood keep forcing the thyroid tissues to expand in an attempt to improve the absorption of iodine.
Thyroid Cancer
Three out of every twenty thyroid nodules that develop in the population are malignant or cancerous. Thyroid nodules that end up being malignant upon tissue biopsy will be papillary cancer, the most prevalent form of thyroid cancer. When thyroid nodules are discovered, they are almost always evaluated further using diagnostic imaging tests and or tissue biopsies to rule out or confirm malignancy. Individuals affected by thyroid nodules with any solid content are at a greater risk of developing thyroid cancer. The increased opportunity for carcinogenesis-inducing cellular DNA mutation is the result of the thyroid tissue overgrowth that causes nodules to form. The risk of cancer-causing cellular DNA mutation increases as the general activity of the cell division process in the thyroid gland increases. Thyroid nodules that are continually going through changes are more likely to undergo carcinogenesis than smaller nodules that change gradually or not at all.
Hyperthyroidism
Not only can thyroid nodules be classified as benign or cancerous, but they are also classified as toxic or non-toxic. A thyroid nodule that develops in an affected individual that produce symptoms characteristic of an overactive thyroid is said to be an adenoma or toxic thyroid nodule. Toxic thyroid nodules account for between three and five percent of all individuals affected by hyperthyroidism. Hyperthyroidism that arises due to a toxic thyroid nodule is more prevalent among women who are past their sixth decade of life, and rarely ever occurs in children. Nodule precipitated hyperthyroidism can produce problems in the cardiovascular system, including rapid heart rate, atrial fibrillation, and congestive heart failure. The types of nodules that induce hyperthyroidism can cause an affected individual to experience bone loss and osteoporosis.
Issues Swallowing Or Breathing
An individual who experiences the development of thyroid nodules may experience issues with swallowing or breathing as a result of their abnormal growth. Problems with breathing and swallowing occur as a direct result of the thyroid gland becoming larger than normal. Thyroid nodules are abnormal growths of the thyroid tissues that cause marked increases in the volume, size, and mass of the organ. Multinodular goiters are notorious for producing physical symptoms related to size. Only around one-third of all cases of thyroid nodules cause symptoms related to swallowing and breathing. Some patients who have a thyroid nodule have described it to cause a sensation that makes them want to swallow repeatedly or have a constant urge to swallow something. When a thyroid nodule compresses the tissues of the throat, a patient may have a frequent urge to cough or clear their throat from partial obstruction or narrowing of the windpipe. Uncomfortable pressure on the trachea that makes the action of breathing tickle or feel abnormal is also a manifestation of thyroid nodules.