Thyrotoxicosis signifies an excessive amount of thyroid hormone circulating in the body. This condition is also characterized by a low level of thyroid-stimulating hormone (TSH) in the bloodstream, as the pituitary gland detects sufficient thyroid hormone levels.

The most frequent cause of hyperthyroidism is Graves’ Disease. In this autoimmune disorder, the immune system, for reasons not fully understood, releases antibodies that target or “bind” to thyroid cells. This process stimulates the thyroid gland, leading to its growth and the production of elevated levels of thyroid hormone.

Graves’ Disease is also known as diffuse toxic goiter because it affects the entire thyroid gland (diffuse), can cause individuals to appear flushed (toxic), and results in an enlarged gland (goiter).

Causes

• Hyperthyroidism, also referred to as an overactive thyroid, is the most common cause of Thyrotoxicosis. It occurs when the thyroid gland produces an excessive amount of thyroid hormone.

• Thyrotoxicosis can also arise from inflammation of the gland (thyroiditis) or from consuming too much thyroid medication. In these instances, the thyroid gland itself is not overactive, but there is still an excess of thyroid hormone in the blood.

• Exogenous ingestion of thyroid hormones (long-term use of synthetic hormone) is associated with Thyrotoxicosis.

• A functioning toxic adenoma of the thyroid gland.

• Adenoma of the pituitary gland.

Signs and symptoms

Mild Thyrotoxicosis may initially present without any symptoms. Symptoms associated with more severe cases include:

• Nervousness

• Irritability

• Fatigue

• Rapid heartbeat

• Weight loss

• Insomnia

• Hair thinning

• Thin skin

• Intolerance to heat

• Increased perspiration

• Muscle aches

• Weakness in upper arms and thighs

• More frequent bowel movements

• Reduced menstrual flow

• Eye irritation or inflammation; “bulging” eyes

Treatment

Treatment for Thyrotoxicosis is tailored to the patient’s age, the underlying cause and severity of the illness, and any other existing medical conditions.

Drugs

Two “antithyroid” medications are available to manage hyperthyroidism. These drugs work by inhibiting the thyroid gland’s production of thyroid hormone. Medications used for this purpose include methimazole (Tapazole) and propylthiouracil (PTU).

Beta-adrenergic blocking agents can alleviate some of the symptoms of thyrotoxicosis. These drugs include propranolol (Inderal), atenolol (Tenormin), metoprolol (Lopressor), and nadolol (Corgard). They are typically used in conjunction with other treatments for thyrotoxicosis.

Radioactive iodine

Treatment involving permanent damage to the thyroid cells that produce thyroid hormone may be necessary. This can be achieved through the use of radioactive iodine, which has been established as a treatment regimen.

Radioactive iodine is a tasteless and odorless substance administered orally in capsule or liquid form. Once ingested, it is absorbed into the bloodstream and taken up by the overactive thyroid cells. Over several weeks, the thyroid gland will diminish in size, and blood levels of thyroid hormone and thyroid-stimulating hormone (TSH) will normalize.

Note: Most patients who undergo radioactive iodine therapy eventually develop hypothyroidism because their thyroid gland does not produce sufficient thyroid hormone. This condition is managed with daily thyroid hormone replacement therapy.

Surgery

Surgical removal of all or part of the thyroid gland may be recommended. Partial removal (lobectomy) is considered if one or more nodules on the gland are overactive. However, if many nodules are involved or if the entire thyroid gland is overactive, the physician may suggest removing most or all of it (subtotal or total thyroidectomy).

Surgery to remove one lobe of the thyroid is termed a lobectomy. Sometimes, the central connecting portion (isthmus) is also removed (isthmusectomy). A subtotal thyroidectomy involves removing most of the gland, while a total thyroidectomy entails removing the entire gland.

Diagnosis of thyrotoxicosis

• The serum TSH value is typically decreased, and measurements of free thyroxine (T4​), free thyroxine index, or free triiodothyronine (T3​), or both, are elevated.

• A scan may be beneficial in distinguishing between Graves’ disease (characterized by diffuse uptake) and toxic multinodular goiter.

Complications

If left untreated, thyrotoxicosis can lead to severe medical complications such as heart rhythm disturbances and osteoporosis, which result from the long-term effects of hormone overproduction.