1. Hyperthyroidism

Hyperthyroidism (overactive thyroid) is a condition in which your thyroid gland produces too much of the hormone thyroxine. Hyperthyroidism can accelerate your body’s metabolism significantly, causing sudden weight loss, a rapid or irregular heartbeat, sweating, and nervousness or irritability.

Causes
A number of conditions, including Graves’ disease, toxic adenoma, Plummer’s disease (toxic multinodular goiter) and thyroiditis, can cause hyperthyroidism.

How it all works

Reasons for too much thyroxine (T-4)

Normally, your thyroid releases the right amount of hormones, but sometimes it produces too much T-4. This may occur for a number of reasons, including:

  • Graves’ disease. Graves’ disease, an autoimmune disorder in which antibodies produced by your immune system stimulate your thyroid to produce too much T-4, is the most common cause of hyperthyroidism. Normally, your immune system uses antibodies to help protect against viruses, bacteria and other foreign substances that invade your body. In Graves’ disease, antibodies mistakenly attack your thyroid and occasionally attack the tissue behind your eyes (Graves’ ophthalmopathy) and the skin, often in your lower legs over the shins (Graves’ dermopathy). Scientists aren’t sure exactly what causes Graves’ disease, although several factors — including a genetic predisposition — are likely involved.
  • Hyperfunctioning thyroid nodules (toxic adenoma, toxic multinodular goiter, Plummer’s disease). This form of hyperthyroidism occurs when one or more adenomas of your thyroid produce too much T-4. An adenoma is a part of the gland that has walled itself off from the rest of the gland, forming noncancerous (benign) lumps that may cause an enlargement of the thyroid. Not all adenomas produce excess T-4, and doctors aren’t sure what causes some to begin producing too much hormone.
  • Thyroiditis. Sometimes your thyroid gland can become inflamed for unknown reasons. The inflammation can cause excess thyroid hormone stored in the gland to leak into your bloodstream. One rare type of thyroiditis, known as subacute thyroiditis, causes pain in the thyroid gland. Other types are painless and may sometimes occur after pregnancy (postpartum thyroiditis).
  • Sudden weight loss, even when your appetite and the amount and type of food you eat remain the same or even increase
  • Rapid heartbeat (tachycardia) — commonly more than 100 beats a minute — irregular heartbeat (arrhythmia) or pounding of your heart (palpitations)
  • Increased appetite
  • Nervousness, anxiety and irritability
  • Tremor — usually a fine trembling in your hands and fingers
  • Sweating
  • Changes in menstrual patterns
  • Increased sensitivity to heat
  • Changes in bowel patterns, especially more frequent bowel movements
  • An enlarged thyroid gland (goiter), which may appear as a swelling at the base of your neck
  • Fatigue, muscle weakness
  • Difficulty sleeping
  • Skin thinning
  • Fine, brittle hair

Older adults are more likely to have either no signs or symptoms or subtle ones, such as an increased heart rate, heat intolerance and a tendency to become tired during ordinary activities. Medications called beta blockers, which are used to treat high blood pressure and other conditions, can mask many of the signs of hyperthyroidism.

Graves’ ophthalmopathy

Sometimes an uncommon problem called Graves’ ophthalmopathy may affect your eyes, especially if you smoke. In this disorder, your eyeballs protrude beyond their normal protective orbits when the tissues and muscles behind your eyes swell. This pushes the eyeballs forward so far that they actually bulge out of their orbits. This can cause the front surface of your eyeballs to become very dry. Eye problems often improve without treatment.

Signs and symptoms of Graves’ ophthalmopathy include:

  • Protruding eyeballs
  • Red or swollen eyes
  • Excessive tearing or discomfort in one or both eyes
  • Light sensitivity, blurry or double vision, inflammation, or reduced eye movement.

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