Causes of Hyperthyroidism

Causes

[ Primary hyperthyroidism ] · Graves' disease   · Toxic multinodular goiter   · Toxic adenoma · Metastasis of functioning thyroid carcinoma · Activating mutation of the TSH receptor (autosomal dominant)   · Ovarian struma   · Drugs: excess iodine

[ Secondary hyperthyroidism ] · TSH-secreting pituitary adenoma   · Thyroid hormone resistance syndrome · Chorionic gonadotropin-secreting tumor   · Gestational thyrotoxicosis

1. Graves' disease (Graves' disease) Graves' disease, the most important cause of hyperthyroidism (60-80%), is named after the person who first studied it. Because Graves' disease accounts for most cases of hyperthyroidism, the terms hyperthyroidism and Graves' disease are often used interchangeably.

Graves' disease occurs due to an autoimmune reaction caused by antibodies that recognize part of the body's own tissues as an antigen and react to it. Antibodies that stimulate the thyroid are present in high concentrations in the patient's blood, and these antibodies continuously stimulate the thyroid, causing large amounts of thyroid hormone to be secreted and producing symptoms of hyperthyroidism.

Graves' disease commonly develops in people in their 20s to 40s, and occurs 4-8 times more often in women than in men. It occurs at a rate of 0.3-2 cases per 1,000 people per year, and is more common in regions with high iodine intake, so it is also a common disease in Korea. Symptoms usually appear gradually over several weeks or months, but in some cases they may appear suddenly.

2. Toxic nodular goiter (Toxic nodular goiter) This refers to a case in which a rarely occurring thyroid nodule produces excessive thyroid hormone and causes hyperthyroidism. It is a rare disease in Korea. Unlike Graves' disease, in which the thyroid gland enlarges uniformly, multiple nodules form in the thyroid.

The symptoms are the same as those of Graves' disease, but are relatively milder, and exophthalmos does not occur. When antithyroid drugs are used, the increased thyroid hormone returns to normal and symptoms disappear, but if the medication is stopped, toxic symptoms reappear. This disease can never be completely cured with antithyroid drugs alone, no matter how long they are taken, so treatment requires radioactive iodine administration or surgery.

Usually, simple radioactive iodine therapy is used, but if the nodule is quite large, surgery is performed. When radioactive iodine is administered, a larger dose is given than when treating Graves' disease, and the later possibility of hypothyroidism is low, at about 10-20%. Surgery is relatively simple when there is a single nodule, as only the part with the nodule is removed, and there are almost no complications. There is no recurrence after surgery, and the occurrence of hypothyroidism is also low.

3. Toxic multinodular goiter (Toxic multinodular goiter) Diffuse toxic multinodular goiter is thought to be caused by iodine deficiency, and symptoms appear as thyroid hormone production increases in the nodules. About 5-10% of patients with this disease progress to a malignant tumor, so careful follow-up examinations and fine-needle aspiration are necessary.

So far, I have explained the causes of hyperthyroidism. In the next part, we will look at the symptoms and diagnosis of hyperthyroidism.

Source: Korea Centers for Disease Control and Prevention, National Health Information Portal