A raised level of thyroid hormone is called as hyperthyroidism. It has various causes but Graves’ disease is the most common cause. Hyperthyroidism can produce various symptoms. Thyroxine is a body chemical (hormone) made by the thyroid gland. It is carried around the body in the bloodstream. It helps to keep the body’s functions (the metabolism) working at the correct pace. Many cells and tissues in the body need thyroxine to keep them going correctly.

In an overactive thyroid gland, your thyroid gland makes too much thyroxine. The extra thyroxine causes many of your body’s functions to speed up. (In contrast, if you have hypothyroidism, you make too little thyroxine; this causes many of the body’s functions to slow down.) Thyrotoxicosis is a term that may be used by doctors instead of hyperthyroidism. The two terms mean much the same.

Causes

Many conditions can cause hyperthyroidism, including Graves’ disease, toxic adenoma, Plummer’s disease (toxic multinodular goiter) and thyroiditis. Your thyroid is a butterfly-shaped gland situated at the base of your neck, just below your Adam’s apple. Although it weighs less than an ounce, the thyroid gland has an enormous impact on your health. Every aspect of your metabolism is regulated by thyroid hormones.

Thyroxine hormone has two type, thyroxine (T-4) and triiodothyronine (T-3), that influence every cell in your body. They maintain the rate at which your body uses fats and carbohydrates, help control your body temperature, influence your heart rate, and help regulate the production of protein. Your thyroid also produces calcitonin, a hormone that helps regulate the amount of calcium in your blood.

Too much thyroxine (T-4) can be released due to many reasons, including:

  • Graves’ disease. It is 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). Hyperthyroidism of this form 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. Inflammation of thyroid gland for unknown reasons can result in hyperthyroidism. 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).

Risk factors

Talk to your doctor if any of your family members has hyperthyroidism particularly Graves’ disease, tends to run in families and is more common in women than in men.

Symptoms

Many other disorders can be mimicked by hyperthyroidism, which may make it difficult for your doctor to diagnose. It can also cause a wide variety of signs and symptoms, including:

  • Suddenly losing weight, even when your appetite and the amount and type of food you eat remain the same or even increase
  • Accelerated 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

Aged people 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

Rarely, Graves’ ophthalmopathy may affect your eyes, especially if you smoke. It is a rare disorder 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.

Graves’ ophthalmopathy presents with:

  • 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