Overactive thyroid, also known as hyperthyroidism, is the condition wherein abnormally elevated levels of thyroid hormones are present in the circulation. Thyroid hormones control the metabolic rate or activity level of the body's cells. Hyperthyroidism increases the metabolic rate, causing characteristic symptoms such as weight loss, jitteriness, rapid heartbeat and hand tremors. Many disorders can cause an overactive thyroid, including autoimmune disease, tumors and inflammatory conditions. Diagnosis of the disorder causing an overactive thyroid will help your doctor devise an appropriate treatment plan.
Toxic Diffuse Goiter
Toxic diffuse goiter, also known as Graves' disease, is the most common cause of overactive thyroid, reports "The Merck Manual for Healthcare Professionals." This condition is an autoimmune disease wherein the immune system stimulates the gland to overproduce thyroid hormones. Notably, this condition may occur concurrently with other autoimmune diseases such as pernicious anemia and type 1 diabetes mellitus.
Toxic Nodular Goiter
Toxic nodular goiter, also known as Plummer's disease, is characterized by islands of thyroid tissue that overproduce thyroid hormones. According to the University of Maryland Medical Center, this disorder most commonly occurs in people older than age 60.
Pituitary Adenoma
UCLA Neurosurgery explains that a pituitary adenoma is a benign tumor of the pituitary gland. The pituitary is often called the master gland because it secretes hormones that control other hormone-producing tissues. Some pituitary adenomas secrete abnormal amounts of thyroid stimulating hormone or TSH. The excessive TSH causes thyroid overactivity.
Subacute Thyroiditis
The American Association of Clinical Endocrinologists notes subacute thyroiditis is an inflammatory condition of the thyroid gland. The inflammation causes excessive release of thyroid hormones into the circulation. The thyroid is usually enlarged and tender with subacute thyroiditis. This condition is usually temporary, resolving spontaneously within a few months.
Silent Thyroiditis
Silent thyroiditis is another form of inflammatory hyperthyroidism. This painless condition most commonly occurs in women three to four months after having a baby, although it can occur outside of the postpartum period. "The Merck Manual for Healthcare Professionals" explains the typical course for this condition is a period of hyperthyroidism followed by an interval of decreased thyroid function or hypothyroidism. In most cases, spontaneous recovery to normal thyroid function occurs. Uncommonly, the hypothyroid state becomes permanent.
Molar Pregnancy
The American Congress of Obstetricians and Gynecologists explains that a molar pregnancy is rare condition wherein the development of the placenta goes awry, causing a growing mass of abnormal tissue in the womb. This tissue produces abnormally large amounts of the pregnancy hormone human chorionic gonadotropin or hCG. This hormone stimulates the thyroid gland, causing hyperthyroidism. Removal of the abnormal tissue halts hCG production, and thyroid gland function returns to normal.
