Hyperthyroidism

Hyperthyroidism


Definition

Hyperthyroidism (overactive thyroid) is a condition in which the thyroid gland produces the high level of the hormone thyroxine. In other words, it can be called as overreactive thyroid. The thyroid gland is an organ located in the front of your neck and releases hormones that control your metabolism (the way your body uses energy), breathing, heart rate, nervous system, weight, body temperature, and many other functions in the body. When the thyroid gland is overactive (hyperthyroidism) the body’s processes speed up and you may experience nervousness, anxiety, rapid heartbeat, hand tremor, excessive sweating, weight loss, and sleep problems, among other symptoms.

Pathophysiology

In hyperthyroidism, serum T3 usually increases more than does T4, probably because of increased secretion of T3 as well as the conversion of T4 to T3 in peripheral tissues. In some patients, only T3 is elevated (T3 toxicosis).
T3 toxicosis may occur in any of the usual disorders that cause hyperthyroidism, including Graves’ disease, multinodular goitre, and the autonomously functioning solitary thyroid nodule.
If T3 toxicosis is untreated, the patient usually also develops laboratory abnormalities typical of hyperthyroidism (ie, elevated T4 and 123I uptake). The various forms of thyroiditis commonly have a hyperthyroid phase followed by a hypothyroid phase.

Causes

A variety of conditions can cause hyperthyroidism. Graves’ disease, an autoimmune disorder, is the most common cause of hyperthyroidism. It causes antibodies to stimulate the thyroid to secrete too much hormone. Other causes of hyperthyroidism include:
  • Excess iodine, a key ingredient in T4 and T3
  • Thyroiditis, or inflammation of the thyroid, which causes T4 and T3 to leak out of the gland
  • Tumours of the ovaries or testes
  • Benign tumours of the thyroid or pituitary gland
  • Large amounts of tetraiodothyronine taken through dietary supplements or medication

Risk factors

  • Have a family history of thyroid disease
  • Have other health problems, including
  • Pernicious anaemia, a condition caused by a vitamin B12 deficiency
  • Type 1 diabetes
  • Primary adrenal insufficiency, a hormonal disorder
  • Eating large amounts of food containing iodine, such as kelp, or use medicines that contain iodine, such as amiodarone, a heart medicine
  • Older than age 60, especially if you are a woman
  • Pregnant within the past 6 months

Clinical manifestations

The symptoms of hyperthyroidism include the following:
  • An enlarged thyroid gland (goitre), which may appear as a swelling at the base of your neck
  • Fatigue or muscle weakness
  • Light periods or skipping periods.
  • Weight loss
  • Hand tremors
  • Mood swings
  • Rapid heartbeat
  • Nervousness or anxiety
  • Trouble sleeping
  • Protruded eyeballs
  • Skin dryness
  • fine, brittle hair
  • Heart palpitations or irregular heartbeat
  • Increased frequency of bowel movements
  • Breast development in men

Complications

  • Heart problems include atrial fibrillation and congestive heart failure
  • An irregular heartbeat that can lead to blood clots, stroke,
  • Brittle bones like osteoporosis
  • Graves’s ophthalmology may exhibit eye problems including bulging, red or swollen eyes, sensitivity to light, and blurring or double vision.
  • Red, swollen skin.
  • Thyrotoxic crisis.

Diagnosis and Test

Thyroid function blood test
Thyroid function test is performed using a sample of blood obtained from the patient with hyperthyroidism. It is used to check the levels of:
  • Thyroid-stimulating hormone (TSH) – a hormone produced by the pituitary gland (a gland at the base of the brain) that controls the production of thyroid hormones
  • Triiodothyronine (T3) – one of the main thyroid hormones
  • Thyroxine (T4) – another of the main thyroid hormones
Your levels will be compared to what’s normal for a healthy person. A low level of TSH and high levels of T3 and/or T4 usually means you have an overactive thyroid.
Radioactive Iodine Uptake Test
To detect the way thyroid gland takes in and absorbs the orally given iodine dose and uses it to produce thyroid hormones. Conclusions are drawn based on the results obtained in this test.
Thyroid scan
  • A dye-injection or oral iodine dose test that enables visualization of the thyroid gland, which is seen on a computer. It helps to detect whether a region of the thyroid gland or the entire gland is affected.
  • Ultrasound Scan – To detect the enlargement of the thyroid gland and surrounding structures.
  • CT or MRI Scan – Scanning specified region if a tumour is suspected.

Treatment and Medications

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:
Drugs known as antithyroid agents-methimazole (Tapazole®) or in rare instances propylthiouracil (PTU)-may be prescribed to treat the hyperthyroidism by blocking the thyroid glands to secrete thyroid hormones. Methimazole is preferred due to less severe side-effects. These drugs work well to control the overactive thyroid, and do not cause permanent damage to the thyroid gland.
Radioactive Iodine:
Another way to treat hyperthyroidism is to damage or destroy the thyroid cells that make thyroid hormone. Because these cells need iodine to make thyroid hormone, they will take up any form of iodine in your bloodstream, whether it is radioactive or not.
The radioactive iodine used in this treatment is administered by mouth, usually in a small capsule that is taken just once. Once swallowed, the radioactive iodine gets into the bloodstream and rapidly it is taken up by the overactive thyroid cells.
The radioactive iodine that is not taken up by the thyroid cells disappears from the body within days over a period of several weeks to several months (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.
Thyroid surgery:
Hyperthyroidism can be permanently cured by surgical removal of all or most of the thyroid gland. This procedure is best performed by a surgeon who has experience in thyroid surgery. An operation could be risky unless the hyperthyroidism is first controlled by an anti-thyroid drug or a beta-blocking drug, usually for few days before surgery, a surgeon may prescribe to take drops of nonradioactive iodine-either Lugol’s iodine or supersaturated potassium iodide (SSKI). This extra iodine reduces the blood supply to the thyroid gland and thus makes the surgery easier and safer.
Beta-Blockers:
Beta blockers do not stop thyroid hormone production but can reduce symptoms until other treatments take effect. Beta blockers act quickly to relieve many of the symptoms of hyperthyroidism, such as tremors, rapid heartbeat, and nervousness. Most people feel better within hours of taking beta blockers.
Propranolol (Inderal®) was the first of these drugs to be developed. Some physicians now prefer related, but longer-acting beta-blocking drugs such as atenolol (Tenormin®), metoprolol (Lopressor®), nadolol (Corgard®), and Inderal-LA® because of their more convenient once- or twice-a-day dosage.

Prevention and Cure

  • Patients being treated for hyperthyroidism need to follow-up with the physician for regular monitoring. For weight loss, fatigue and other complaints a proper nutritional plan is essential.
  • To prevent further weakness, bone thinning and to maintain good health, it is necessary to follow a proper diet plan and healthy routine as advised by the physician.
  • Taking calcium and vitamin D supplements may be considered with medical advice. Regular exercise can help to improve bone and heart health.
  • For those suffering from eye disturbances or Grave’s ophthalmology, special care of the eyes can help.
  • Some measures include wearing sunglasses, applying cool eye compresses, using lubricating eye drops and raising the head while sleeping to relieve pressure on the eyes.

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