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Causes of exophthalmos

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Thyroid problems are the most common cause of exophthalmos. In particular, Grave's disease - an autoimmune disease that causes the thyroid gland to produce an excess amount of thyroid hormone (hperthyroidism) - is often associated with exophthalmos.

In exophthalmos, an increase in the amount of white cells (lymphocytes) in the eye, plus the inflammation and swelling that occurs as a result of an excess amount of thyroid hormone, results in the eyeballs being forced forward out of the eye sockets (orbits).

The thyroid gland

The thyroid gland is located in the neck, just below the Adam's apple. It is one of the body's endocrine glands which produce hormones (chemicals) that control the body's metabolism (the rate at which the body uses energy). Thyroxine and triiodothyronine are the thyroid hormones that are produced by the thyroid gland.

Thyroid eye disease

Thyroid eye disease - sometimes known as thyroid orbitopathy (TO) - is a condition that affects the soft tissues and muscles that surround the eyes. The tissues of the eyes become swollen and inflamed. Thyroid eye disease is usually associated with an over-active thyroid gland (hyperthyroidism) or, sometimes, an under-active thyroid gland (hypothyroidism).

Autoimmune diseases

The immune system is the body's natural defence system. It releases antibodies to help fight off infection and disease. However, an autoimmune disease, such as Grave's disease, causes the immune system to produce auto-immune antibodies which attack healthy cells and tissue. The exact reason why this occurs is unknown. If the auto-immune antibodies attack the thyroid gland, the thyroid gland will react by producing more thyroid hormones. The autoimmune antibodies and excess thyroid hormone can attack the soft tissues and muscles surrounding the eyes, causing eye problems such as:
  • dry, 'gritty' eyes,
  • redness,
  • puffiness,
  • swelling and inflammation,
  • vision problems, and
  • bulging eyeballs (exophthalmos).

Hereditary diseases

As autoimmune diseases, such as Grave's disease, are hereditary, exophthalmos may also run in families. Exophthalmos does not always occur at the same time that thyroid gland problems, such as hyperthyroidism, or hypothyroidism, occur. It may occur months or, sometimes, years afterwards. However, sometimes, exophthalmos can occur before thyroid problems develop.

Proptosis

Proptosis (protrusion of one eyeball) may be caused by the presence of other material in the eye socket, such as:
  • a cancer,
  • a mucus-filled cyst (mucocoele),
  • a brain tumour, or
  • a blood clot.

Proptosis may also develop as a result of an injury (trauma) to the eye, or an infection in the sinuses.

If you notice that one, or both, of your eyeballs are protruding, you should seek medical advice immediately. It is important to remember that in many cases tumours are benign.

Glossary

  • Brain: The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.
  • Thyroid: The thyroid is a jointed piece or cartilage that enclosed the vocal cords and forms the 'Adam's apple' in men.
  • Benign: Benign refers to a condition that should not become life-threatening. In relation to tumours, benign means not cancerous.
  • Cyst: A cyst is a fluid-filled sac or cavity in the body.
  • Blood: Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
  • Thyroid gland: The thyroid gland in the throat makes hormones to help control growth and metabolism (the process that turns the food we eat into energy).
  • Tissue: Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.  
  • White cells: White blood cells are the part of blood that fight infection and disease.
  • Antibodies: Antibodies and immunoglobins are proteins in the blood. They are produced by the immune system to fight against bacteria, viruses and disease.
Medical Review: November 27, 2008

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