HYPERTHYROIDISM

HYPERTHYROIDISM

Definition:

Hyperthyroidism is more correctly called thyrotoxicosis and results from elevations in the concentration of thyroid hormones in the blood. It results in illness due to acceleration of body metabolism.

Symptoms:

No two patients have the exact symptom complex, and severity of symptoms can vary considerably. Most common symptoms include:

  • Fatigue
  • Weight loss
  • Palpitations
  • Shortness of breath
  • Tremors
  • Heat intolerance
  • Excessive sweating
  • Anxiety
  • Insomnia
  • Frequent bowel movements
  • Menstrual irregularities
  • Hair loss

Causes of Hyperthyroidism:

Graves Disease

Graves Disease is the most common cause of hyperthyroidism. It is a condition in which the immune system mistakenly targets the thyroid gland and forms antibodies that turn on the thyroid gland. The factory in the thyroid that makes thyroid hormone gets stuck in high gear. It results in enlargement of the thyroid gland in most cases. Many patients with Graves Disease have other family members with thyroid disease of one kind or another. It usually affects women between the ages of 20 and 40, but can occur in both men and women at virtually any age. Graves Disease can affect the eyes in a small number of patients (Graves Ophthalmopathy). In this condition, patients may experience dryness, redness or itching of the eyes. In the worst cases, swelling occurs behind the eyes that can cause bulging eyes.

Hot Nodules

Hyperthyroidism may be caused by one or more non-cancerous nodules in the thyroid gland that over-produces thyroid hormone.

Subacute Thyroiditis

This condition is thought to result from a virus that results in inflammation of the thyroid gland. Subacute thyroiditis is often preceded by a upper respiratory illness. The thyroid may or may not be enlarged, but frequently is tender. The inflammation in the gland causes thyroid hormone to leak into the blood stream in an uncontrolled fashion. Hyperthyroidism is temporary in this condition and resolves once the viral infection has resolved.

Lymphocytic Thyroiditis and Post-Partum Thyroiditis

Like subacute thyroiditis, this condition results in inflammation of the thyroid that results in the uncontrolled leakage of stored thyroid hormone into the blood. It is usually painless and is caused by antibodies of the immune system attacking the thyroid gland. It often occurs after delivery. There is frequently a family history of thyroid disease in affected patients: women are affected more frequently than men. Hyperthyroidism is usually temporary, lasting several months and may be followed by temporary or permanent hypothyroidism./

Ingested Thyroid Hormone

Taking too much thyroid hormone will result in thyrotoxicosis.


Diagnosis:

A history and physical exam is usually enough to point to a diagnosis of hyperthyroidism. This will always be combined with measurement of thyroid function tests and sometimes a thyroid uptake/scan.

Thyroid Function Tests:

TSH (Thyroid Stimulating Hormone): Patients with hyperthyroidism have low TSH levels. TSH is a pituitary hormone that stimulates the thyroid gland to make more thyroid hormone. If thyroid hormone levels are high, the pituitary will turn off TSH production.

Free T4: T4 is the main thyroid hormone. Free T4 levels are usually elevated, but on occasion are in the upper end of the normal range in mild cases.

Free T3: T3 is an additional thyroid hormone that is usually elevated in hyperthyroid patients.

Thyroid Uptake and Scan:

Uptake: This is a test that is performed in two steps. Radioactive iodine is administered to the patient as a capsule and then uptakes are taken 4–6 and 24 hours later. The uptake uses a Geiger counter to see what portion of the radioactive iodine was trapped in the thyroid gland.

Scan: A scan generates a picture of the thyroid that shows which parts of the thyroid the iodine was taken into.

Uptakes are elevated in patients with Graves Disease and hot nodules. The scan will show iodine throughout the gland in Graves Disease and iodine in only one spot in patients with a hot nodule. Uptakes are very low in patients with subacute thyroiditis, lymphocytic thyroiditis, or excessive thyroid hormone ingestion.


Treatment:

Surgery:

Surgery is rarely used to treat hyperthyroidism. However it is the most rapid treatment to correct hyperthyroidism. It must be performed by a highly experienced surgeon and coordinated closely with the treating endocrinologist.

Medications:

Anti-Thyroid Drugs: Methimazole (Tapazole) and propothiouracil (PTU) are medications that slow down the production of thyroid hormone by the thyroid gland. They will only work to treat hyperthyroidism caused by Graves Disease or hot nodules. Once the medication is stopped the hyperthyroidism will return. Although some patients use this treatment on a long-term basis, they are usually short-term treatments. Side effects include rashes, joint pains, and liver inflammation. A serious complication called agranulocytosis (loss of white blood cells) can result in life-threatening infections, but fortunately this is rare (less than 1/50,000 patients). Only PTU is recommended in pregnancy. Therapy with these medications requires frequent monitoring of blood tests.

Beta-Blockers: These drugs help to decrease the symptoms of hyperthyroidism without actually lowering the levels of thyroid hormone in the blood. They are effective for controlling symptoms in all forms of hyperthyroidism, but do not treat the underlying disease.

Radioactive iodine: Hyperthyroidism caused by Graves Disease or hot nodules can be treated by administering radioactive iodine in the mouth. The overactive thyroid takes up the radioiodine and is destroyed by the radiation. It usually takes 1–3 months for the thyroid to be destroyed. Ten percent of patients require more than one treatment. This treatment results in permanent hypothyroidism and life-long dependence on thyroid hormone replacement therapy (Synthroid, Levoxyl, etc.) In essence, we trade a difficult to treat disease (hyperthyroidism) for a more easily managed disease (hypothyroidism). This treatment does not increase the risk of cancer. Women should delay pregnancy for at least 6 and preferably 12 months after treatment.