A small butterfly-shaped gland located beneath the skin in the middle portion of the neck is called the thyroid. It produces thyroid hormones that regulate cellular metabolism. Overproduction or underproduction of thyroid hormones causes a constellation of symptoms that range from general fatigue to alarming symptoms involving cardiac abnormalities. Oftentimes, disease may go undetected if symptoms are mild. Thyroid disease is more common in women than men. The causes of thyroid disease include autoimmune, inflammation and abnormal benign and cancerous growths.
Autoimmune Disorders
Hashimoto's is an autoimmune disorder in which the body's defense system makes antibodies against the thyroid. This causes a failure of the thyroid to produce necessary thyroid hormones. Patients may present with early to late symptoms of weight gain, puffy face or muscle and joint pain to name a few listed by UCLA Health System. Treatment is aimed at replacing absent thyroid hormone. Hashimoto's is the most common thyroid disease in the United States.
Grave's disease is the most common cause of hyperthyroidism. Grave's disease is an autoimmune disorder wherein antibodies attach to receptors on the thyroid, abnormally stimulating production of thyroid hormones. Common presenting symptoms include those symptoms associated with hyperthyroidism, such as increased sweating, increased appetite, unexplained weight loss, rapid heart rate and atrial fibrillation, as listed by the National Institutes of Health. A goiter may or may not be present.
Inflammatory Causes
Silent lymphocytic thyroiditis, or inflammation of the thyroid gland, is a variant of Hashimoto's. It is an unknown cause of destruction of the thyroid. Release of stored thyroid hormones circulate the blood, causing hyperthyroid symptoms. Afterward, hypothyroid symptoms occur. The symptoms may wax and wane based on the availability of iodine. It typically resolves on its own after a year.
Nodular Causes
Toxic nodular goiter (Plummer's Disease), or abnormal stimulation of the thyroid, is thought to be triggered by viral illness, as it typically occurs after respiratory or gastrointestinal infection. Symptoms can be both hypothyroid or hyperthyroid related.
Cancer Causes
Papillary carcinoma is the most common cause of thyroid cancer. It is called papillary based on the shape of the abnormal cells that invade the thyroid due to overgrowth, which causes an increase in thyroid hormone. Symptoms include unexplained weight loss and heat intolerance. A goiter may be present. Papillary carcinoma has the best prognosis of all the cancerous causes of thyroid disease.
Interventional Causes
Interventional thyroid disease is a common cause of thyroid disease. Disease directly related to medications, radiation or surgical intervention are considered causes caused by the treatments themselves. Medications used to treat Grave's disease may result in hypothyroidism ,causing the patient to require lifelong treatment for hypothyroidism. Similarly, surgical removal of the thyroid or radiation treatment may result in hypothyroidism.
Other Causes
Iodine deficiency is the most common cause of thyroid disease worldwide. Some developing countries lack iodine in the diet to provide the thyroid with the necessary substrate to produce thyroid.
