Causes of exophthalmos
Thyroid problems are the most common cause of exophthalmos. They are often caused by Graves disease.
The thyroid gland
The thyroid gland is located in the neck, just below the Adam s apple. It produces hormones that control the rate at which the body uses energy (metabolism). Thyroxine and triiodothyronine are the hormones produced by the thyroid gland.
Thyroid eye disease
A condition that affects the thyroid gland, such as an overactive thyroid (hyperthyroidism) or an underactive thyroid (hypothyroidism), can sometimes cause thyroid eye disease. This is also known as thyroid orbitopathy. In rare cases, thyroid eye disease can occur without any problems of the thyroid gland.
Thyroid eye disease affects the soft tissues and muscles that surround the eyes and increases the amount of fluid behind the eyeballs. The tissues around the eyes become swollen and inflamed. This results in the eyeballs being forced forward and out of the eye sockets, causing exophthalmos.
Graves disease is an autoimmune condition (see below) and is the most common cause of an overactive thyroid. It is estimated that up to 30% of people with Graves disease develop thyroid eye disease.
Autoimmune conditions
The immune system is the body s natural defence against infection and illness. It releases white cells, antibodies and other chemicals to help fight infection and disease. In autoimmune conditions such as Graves disease, the body s immune system turns against healthy cells and tissues. The exact reason for this is unknown.
If the autoimmune attack targets the thyroid gland, the thyroid gland may react by producing more thyroid hormones. The autoimmune attack can also involve soft tissues and muscles surrounding the eyes, causing eye problems, such as dry, gritty , swollen eyes and exophthalmos.
Exophthalmos does not always occur at the same time as thyroid gland problems, such as hyperthyroidism or hypothyroidism. It may occur months or years afterwards. Sometimes, exophthalmos can occur before thyroid problems develop and, in rare cases, the thyroid gland is not involved.
Graves disease
Exophthalmos is often caused by Graves disease which:
- can run in families
- can occur at any age
- is most common in women who are 30-40 years of age
- you are more likely to develop if you smoke
Antibodies
Antibodies are proteins that are produced by the body to neutralise or destroy disease-carrying organisms and toxins.
Hormones
Hormones are groups of powerful chemicals that are produced by the body and have a wide range of effects.
Lymphatic system
The lymphatic system is made up of a network of vessels (channels) and glands called lymph nodes that are distributed throughout the body. It helps fight infection.
White blood cells
White blood cells are the part of blood that fight infection and disease.
