Hyperthyroidism is a condition in which an overactive thyroid gland is producing an excessive amount of thyroid hormones {most important are thyroxine (T4) and triiodothyronine (T3)} that circulate in the blood.

Normally, these thyroid hormones regulate the metabolism of cells in the body and when in this condition there is excess production of thyroid hormones leading to disturbance in cell metabolism.

The thyroid gland is located in the lower part of the neck, below the Adam's apple and wraps around the windpipe (trachea) and has a shape that is similar to a butterfly formed by two wings (lobes) and attached by a middle part.

Thyrotoxicosis is a toxic condition that is caused by an excess of thyroid hormones from any cause which can be due to an excessive intake of thyroid hormone or by overproduction of thyroid hormones by the thyroid gland (The term hyperthyroidism and thyrotoxicosis are frequently used interchangeably).

Some common causes of hyperthyroidism include:

• Graves' Disease (most common cause of hyperthyroidism caused by generalized over activity of thyroid gland)
• Functioning adenoma ("hot nodule") and toxic multinodular goiter (TMNG) (a condition in which nodules is produced by thyroid gland which produces thyroid hormones independently)
• Excessive intake of thyroid hormones
• Abnormal secretion of TSH ( hormone produced by pituitary gland which regulates secretion of thyroid hormones from thyroid gland)
• Thyroiditis (inflammation of the thyroid gland)
• Excessive iodine intake

Hyperthyroidism manifest itself by several signs and symptoms; however, patients with mild disease usually experience no symptoms. In general, the symptoms become more obvious as the degree of hyperthyroidism increases. The symptoms usually are related to an increase in the metabolic rate of the body.

Common symptoms include:

• Excessive sweating
• Heat intolerance
• Increased bowel movements
• Tremor (usually fine shaking)
• Nervousness agitation
• Rapid heart rate
• Weight loss
• Fatigue
• Decreased concentration
• Irregular and scant menstrual flow

In older patients, irregular heart rhythms and heart failure can occur. In its most severe form, untreated hyperthyroidism may result in "thyroid storm," a condition involving high blood pressure, fever and heart failure. Mental changes, such as confusion and delirium, also may occur.

The diagnosis of hyperthyroidism is based on basis of complete physical examination by the physician who then decides to go for the specific diagnostic tests which helps him to confirm the diagnosis.

The presence of above mentioned symptoms and signs strongly suggests the need for diagnostic testing for hyperthyroidism which is listed below:

• Blood levels of T3, T4 and TSH: To confirm the presence of excessive thyroid hormone (but this test do not point to a specific cause).
• A combination of antibody screening (for Graves' disease) and a thyroid scan (using radioactively-labelled iodine) to diagnose the underlying thyroid disease.

The treatment of hyperthyroidism includes:

• Treating the symptoms
• Antithyroid drugs
• Radioactive iodine
• Surgery treating symptoms

This includes treating the symptoms with help of medications available. These medications counteract the effect of thyroid hormone to increase metabolism, but they do not alter the levels of thyroid hormones in the blood. One of the main classes of drugs used to treat these symptoms is the beta-blockers [for example; propranolol (Inderal), atenolol (Tenormin), metoprolol (Lopressor)].

For patients with sustained forms of hyperthyroidism, such as Graves' disease or toxic nodular goiter, anti-thyroid medications are often used. The goal with this form of drug therapy is to prevent the thyroid from producing hormones.

In this type of treatment patient is given radioactive iodine by mouth due to which the thyroid cells which absorb this iodine get killed and there is no increase in level of thyroid hormone further. The advantage of this treatment is that there is very little radiation exposure (or side effects) for the rest of the body because iodine is not absorbed by any other cells in the body. This form of therapy often takes one to two months before the thyroid cells have been killed and the radioactive medicine is completely excreted from the body within a few days. The only common side effect of radioactive iodine treatment is underactivity of the thyroid gland and produces a condition called hypothyroidism.

Surgery to partially or completelly remove the thyroid gland but it is not used as frequently as the other treatments for this disease.

The goal is to remove the thyroid tissue that produces the excessive thyroid hormone. But if too much tissue is removed, an inadequate production of thyroid hormone (hypothyroidism) may result.

Hence surgery is indicated in following cases:

• Pregnant patients and children who have major adverse reactions to antithyroid medications.
• Patients with very large thyroid glands and in those who have symptoms from compression of tissues adjacent to the thyroid, such as difficulty swallowing, hoarseness and shortness of breath.