Causes of Thyroid Enlargement

Thyroid enlargement, often referred to as goiter, does not necessarily indicate that the thyroid gland is poorly functioning. In fact, some instances of goiter occur alongside normal hormone production, while others may be associated with excessive or inadequate hormone secretion. There are various factors that can contribute to thyroid enlargement, which will be elaborated upon below.

Iodine Deficiency

According to the World Health Organization, iodine deficiency is the most prevalent cause of thyroid enlargement globally. The relationship between iodine deficiency and goiter arises from the thyroid’s requirement for iodine in the production of its hormones. A deficiency of iodine in the body leads to insufficient hormone production by the thyroid, resulting in noticeably decreased levels of thyroid hormones in the bloodstream. This deficiency signals the pituitary gland to secrete thyroid-stimulating hormone (TSH) to encourage the thyroid to produce its hormones. However, if the thyroid cannot manufacture the hormones due to iodine deficiency, this leads to a type of enlargement known as iodine-deficiency goiter. While iodine deficiency remains the most common cause of goiter worldwide, this is not the case in countries where iodine is added to table salt. In contrast, regions in Southeast Asia, Latin America, and Central Africa experience lower average daily iodine intake. It is important to note that salt is not the only source of iodine; it can also be found in seaweed, cow’s milk, and plants grown in iodine-rich soil.

Hypothyroidism

Thyroid enlargement can also occur in conjunction with hypothyroidism, characterized by decreased hormone production by the thyroid gland. This condition prompts the pituitary gland to stimulate the thyroid for increased hormone output, resulting in gland enlargement. The most common cause of hypothyroidism is Hashimoto’s thyroiditis, an autoimmune disorder where the immune system mistakenly attacks the thyroid cells, impairing hormone production. As levels of thyroid hormones drop in the blood, the pituitary gland signals the thyroid to produce more hormones, which ultimately leads to the thyroid becoming enlarged. It is noteworthy that Hashimoto’s disease is the primary cause of thyroid enlargement in developed countries, while iodine deficiency remains the most prevalent cause globally. Certain groups are more susceptible to Hashimoto’s disease, including women over the age of 40 and individuals with a family history of this condition.

To learn more about hypothyroidism, you can refer to the following article: (Hypothyroidism: Symptoms and Treatments).

Hyperthyroidism

Another cause of thyroid enlargement is hyperthyroidism, which is characterized by excessive hormone production by the thyroid. This overproduction can lead to overstimulation and subsequent enlargement of the thyroid gland. The most common cause of hyperthyroidism is Graves’ disease, another autoimmune disorder where the immune system mistakenly stimulates the thyroid cells to hypersecrete hormones. In this context, Graves’ disease produces proteins known as thyroid-stimulating immunoglobulins, which increase the size of the thyroid as well as its hormone production, resulting in both enlargement and hyperactivity.

For additional information on hyperthyroidism, refer to the following article: (What is Hyperthyroidism?).

Thyroid Nodules

Thyroid nodules are masses that can develop within the thyroid gland. These nodules can vary in number, appearing as a single nodule or as multiple nodules. They may be filled with fluid, solid material, or a combination of both. Nodules differ widely in size; some are so small that they cannot be felt, while others can be palpable. Smaller nodules are often discovered incidentally during imaging studies for unrelated issues. The prevalence of palpable thyroid nodules is approximately 6% among women and 2% among men, particularly in older adults or those with iodine deficiency. Overall, the prevalence of nodules that can be felt is around 20-76% among the population, according to a 2010 publication in the Australasian Journal of Ultrasound in Medicine. It is important to note that thyroid nodules may contribute to gland enlargement.

Other Causes

In addition to the aforementioned factors, there are other less common causes of thyroid enlargement, including:

Thyroiditis: Inflammation of the thyroid can trigger enlargement, which may stem from an infection.
Hormonal Changes: The status of the thyroid may be influenced by hormonal fluctuations, as seen during puberty, pregnancy, or menopause.
Excessive Iodine Intake: While iodine is vital for thyroid function, excessive consumption of iodine-rich foods can lead to higher concentrations of iodine in the thyroid, increasing the risk of enlargement.
Certain Foods: Regularly consuming specific foods, such as spinach, peanuts, soybeans, and tofu, can impair thyroid function, raising the likelihood of enlargement.
Thyroid Cancer: Although rare, thyroid cancer has the potential to cause enlargement. It is diagnosed accurately through biopsy procedures, in which a sample of thyroid tissue is examined in a laboratory.

Risk Factors for Thyroid Enlargement

Several factors can increase a person’s risk of developing thyroid enlargement, which includes:

Gender: Women are statistically more likely to develop thyroid enlargement compared to men, as supported by numerous global studies.
Age: The prevalence of thyroid enlargement increases after the age of 40.
Family History: Having a family member with thyroid enlargement or autoimmune disorders can elevate the risk.
Smoking: There is a suggested correlation between smoking and an increased risk of thyroid enlargement, due to the presence of thiocyanate in tobacco, which affects the body’s iodine utilization. Notably, smokers with iodine deficiency are at a heightened risk for thyroid enlargement.
Radiation Exposure: The likelihood of developing thyroid enlargement increases with exposure to therapeutic radiation in the neck or chest area, as well as through other forms of radiological evaluation.
Certain Medications: Some medications may heighten the risk of thyroid enlargement, including amiodarone (used for heart arrhythmias) and lithium. A study published in the Journal of Thyroid Research in 2013 indicated that thyroid enlargement is a prominent clinical feature in patients treated with lithium. Of note, 3.6% of patients with bipolar disorder taking lithium experienced thyroid enlargement. However, it is crucial to adhere to prescribed treatment plans and consult healthcare providers before altering or discontinuing any medication, as the benefits of prescribed medications generally outweigh potential side effects.