Alternate Names: Thyrotoxicosis; Overactive thyroid

Causes and Risks:

The thyroid gland is located in the neck and produces several hormones that regulate growth, digestion, and the use of nutrients (metabolism). It is part of the endocrine system.

The thyroid gland responds to complex mechanisms to control the rates of hormone secretion.

Hyperthyroidism or thyrotoxicosis results from excess quantities of thyroid hormone within the body. Rather than being classified as a specific disease, it is classified as a syndrome that describes the characteristics resulting from this condition.

The causes of hyperthyroidism include Graves’ disease; tumors of the thyroid gland, pituitary gland, testes or ovaries; inflammation of the thyroid from a viral infection or other inflammation; ingestion of excessive amounts of thyroid hormone; and ingestion of excessive iodine. Graves’ disease accounts for 85% of all cases of hyperthyroidism.

Risk factors are associated with the causes.

Related topics:

• Painless (silent) thyroiditis
• Factitious hyperthyroidism
• Hypothyroidism

Prevention: There are no general prevention measures to prevent hyperthyroidism, except for avoiding excess iodide ingestion.

Symptoms:

• Weight loss
• Increased appetite
• Nervousness
• Restlessness
• Heat intolerance
• Increased sweating
• Fatigue
• Muscle cramps
• Frequent bowel movements
• Menstrual irregularities in women
• Goiter may be present

• Weakness
• Tongue problems
• Thirst - excessive
• Tearing - increased
• Sleeping difficulty
• Skin - clammy
• Skin - abnormally dark or light
• Skin blushing/flushing
• Pulse - bounding
• Paleness
• Nausea and vomiting
• Loss of muscle function/feeling
• Muscle atrophy
• Movement - uncoordinated
• Menstruation - absent
• Itching - overall
• Heartbeat sensations
• Hand tremor
• Hair loss
• Diarrhea
• Breast development in men
• Bone pain or tenderness
• Blood pressure - high
• Protruding eyes (exophthalmos)

Signs and Tests: Vital signs (temperature, pulse, rate of breathing, blood pressure) show increased heart rate. Systolic blood pressure may be elevated. Physical examination may reveal thyroid enlargement or goiter.

Laboratory tests that evaluate thyroid function:

• Serum TSH is usually decreased
• Serum T3, T4, thyroid resin uptake are usually elevated

• Vitamin B-12
• TSI
• Triglycerides
• RT3U
• Radioactive iodine uptake
• Glucose test
• Cholesterol test
• Antithyroglobulin antibody

Treatment: Treatment will vary depending on the cause of the condition and the severity of symptoms. Hyperthyroidism is usually treated with antithyroid medications, radioactive iodine, or surgery.

Beta-blockers (e.g., propranolol) are used to treat some of the symptoms including rapid heart rate, sweating, and anxiety until the hyperthyroidism is controlled.

Prognosis: Hyperthyroidism caused by Graves’ disease is usually progressive and has associated complications. Recurrences of hyperthyroidism are common. However, hyperthyroidism is generally treatable and rarely fatal.

Complications:

• Cardiac complications include rapid heart rate, congestive failure, and atrial fibrillation.
• Thyroid crisis or "storm" is an acute worsening or exaggeration of the symptoms of hyperthyroidism that may occur with infection or stress. Fever, decreased mental alertness, and abdominal pain may occur and immediate hospitalization is indicated.
• Hyperthyroidism increases the risk for osteoporosis.