The term hyperthyroidism refers to any condition in which there is increased thyroid hormone produced in the body means the thyroid gland is overactive. Another term for this problem is thyrotoxicosis, which refers to high thyroid hormone levels in the blood stream, irrespective of their source.
Symptoms

• Poor concentration
• Fatigue/tiredness
• Frequent bowel movements/Diarrhea
• Goiter (enlarged thyroid gland) or thyroid nodules
• Hair loss
• Hand tremor
• Heat intolerance
• Increased appetite
• Increased sweating
• Irregular menstrual periods in women
• Nervousness
• Pounding or racing heart beat (palpitations)
• Restlessness
• Sleep problems
• Weight loss despite a good appetite

Hyperthyroidism usually begins slowly but in some young patients these changes can be very abrupt. At first, the symptoms may be mistaken for simple nervousness due to stress.

Causes
The most common cause is overproduction of thyroid hormone by the entire thyroid gland. This condition is also known as Graves’ disease(autoimmune disorder). Graves’ disease is caused by antibodies in the blood that turn on the thyroid and cause it to grow and secrete too much thyroid hormone. This type of hyperthyroidism tends to run in families and it occurs more often in young women.
Other common causes include:

• Thyroiditis-Inflammation of the thyroid due to viral infections, some medicines, or after pregnancy .
• Taking too much thyroid hormone can cause thyrotoxicosis.
• Nodules or lumps in the thyroid that may gradually grow and increase their activity so that the total output of thyroid hormone into the blood is greater than normal. This condition is known as toxic nodular or multinodular goiter.
• Some tumors of the testes or ovaries (rare)
• Getting medical imaging tests with contrast dye that has iodine (rare, and only if there is a problem with the thyroid).

Thyroid hormone regulation
The thyroid itself is regulated by another gland located in the brain, called the pituitary. In turn, the pituitary is regulated in part by thyroid hormone that is circulating in the blood (a “feedback” effect of thyroid hormone on the pituitary gland) and in part by another gland called the hypothalamus, also a part of the brain.The hypothalamus releases a hormone called thyrotropin releasing hormone (TRH), which sends a signal to the pituitary to release thyroid stimulating hormone (TSH). In turn, TSH sends a signal to the thyroid to release thyroid hormones. The rate of thyroid hormone production is controlled by the pituitary gland. If there is an insufficient amount of thyroid hormone circulating in the body to allow for normal functioning, the release of TSH is increased by the pituitary and TSH stimulates the thyroid to produce more thyroid hormone. In contrast, when there is an excessive amount of circulating thyroid hormone, the release of TSH is reduced as the pituitary attempts to decrease the production of thyroid hormone.

Diagnosis
Physician will ask questions about your symptoms, do a physical exam with reflexes, medical history, family history and order medical tests to diagnose hyperthyroidism.
Blood tests – to measure your thyroid hormones TSH, T3, and T4. A high level of thyroid hormone in the blood plus a low-level of TSH is common with an overactive thyroid gland.
Imaging tests of the thyroid-If blood tests show that your thyroid is overactive, your doctor may ask for
•   Radioactive iodine uptake and scan
•   Thyroid ultrasound

Treatment
No single treatment is best for all patients with hyperthyroidism. The appropriate choice of treatment will be influenced by your age, the type of hyperthyroidism that you have, the severity of your hyperthyroidism, other medical conditions that may be affecting your health and your own preference.

Antithyroid drugs
Methimazole , Propylthiouracil (PTU)
Methimazole is usually preferred one due to less severe side-effects. These drugs work well to control the overactive thyroid, bring quick control of hyperthyroidism and do not cause permanent damage to the thyroid gland.
Side effects – allergic reactions, red skin rashes, hives, fever and joint pain. Rare but serious condition called Agranulocytosis (decrease number of WBCs). If you are taking one of these drugs and get an infection such as a fever or sore throat, you should stop the drug immediately and check for a white blood cell count that day. Even if the drug has lowered your white blood cell count, the count will return to normal if the drug is stopped immediately. Liver damage is another very rare side effect. You should stop either methimazole or PTU and call your doctor if you develop yellow eyes, dark urine, severe fatigue, or abdominal pain.

Radioactive iodine
Another way to treat hyperthyroidism is to damage or destroy the thyroid cells that make thyroid hormone .The radioactive iodine taken just once by mouth in liquid or capsule form. Once swallowed, the radioactive iodine gets into your blood stream and quickly is taken up by the overactive thyroid cells. The response to treatment can take from 6 to 18 weeks, during which time drug treatment may be used to control hyperthyroid symptoms, radioactive iodine destroys the cells that have taken it up. The result is that the thyroid or thyroid nodules shrink in size, and the level of thyroid hormone in the blood returns to normal. Radioactive iodine is often recommended if you have Graves’ disease and are older than 50, or if you have thyroid nodules (toxic multinodular goiter) that are releasing too much thyroid hormone. Radioactive iodine is contraindicated if:
a. You are pregnant or you want to become pregnant within 6 months of treatment.
b. You are breast-feeding.
c. You have thyroiditis or another kind of hyperthyroidism that is often temporary.
Side effects – side effects of radioactive iodine treatment is for short-term, neck tenderness, swelling, nausea , vomiting, swelling and tenderness of the salivary glands, dry mouth, taste changes.

Beta-blockers
Beta-blocker drugs, such as atenolol or propranolol, do not block the production of thyroid hormone. Instead, they use for symptomatic control of hyperthyroidism, especially rapid heart rate, trembling, anxiety, and the high amount of heat the body produces.

Surgery
Removal of the thyroid gland is another permanent solution, but is often the last option. This procedure must be performed by a highly skilled and experienced thyroid surgeon because of complications include the risk of damage to nerves around the larynx (voice box) and to the nearby parathyroid glands, which control calcium metabolism in the body. Surgery is recommended when there is an enlarged thyroid gland that makes breathing difficult or when antithyroid drugs are not working, or when there are reasons not to take radioactive iodine. It may also be used in people who also have thyroid nodules, especially when the nodules may be cancerous.
Another important thing that after surgical removal of thyroid the source of your hyperthyroidism is gone and you will likely become hypothyroid. As with hypothyroidism that develops after radioiodine treatment, your thyroid hormone levels can be restored to normal by treatment once a day with a thyroid hormone supplement. So the patient will need to be monitored regularly for adequate thyroid hormone levels in the blood.

If left untreated, hyperthyroidism can lead to other health problems including congestive heart failure, abnormal heartbeat, and loss of bone mineral (osteoporosis).

Food to avoid
To increase the effectiveness of your radioactive iodine therapy, you may be prescribed a low iodine diet. The highest sources (and those to be avoided) are iodized salt, grains and cereals, some breads, fish from the sea, shellfish, beef, poultry, pudding mixes, milk and milk products.
Avoid restaurant foods
Consult your doctor before discontinuing or taking any medication.