The thymus gland is a small organ located in the chest between the lungs and behind the breastbone (sternum). This gland increases in size till puberty and then shrinks till it is eventually replaced by fatty tissue. This decline in size is called involution. The main role of the thymus is the production and training of a type of white blood cell (WBC) called T-lymphocytes. The T-lymphocytes are an important part of the immune system that helps fight infections. The thymus gland also acts like an endocrine organ, which means it secretes some hormones such as:
- Thymosin: This hormone helps in T cell production. It also stimulates the pituitary gland to release certain hormones such as the growth hormone (GH).
- Thymopoietin: It helps in T-cell maturation into specific types.
- Thymulin: It enables the formation of specialized T cell types.
- Thymic humoral factor: This hormone boosts the immune response, especially against viral infection.
Can you live without a thymus?
The thymus gland is an important part of the immune system. It trains the white blood cells (WBCs) to recognize the foreign cells and differentiate them from the body cells. The thymus teaches the WBCs when to attack the deformed or abnormal cells and when to stay put. Fortunately, most of its function is complete by the time a baby is born. The gland starts involuting, or becoming less active, after puberty. Thus, the consequences of removing the thymus gland (thymectomy) depend on the age at which the removal is performed. Early removal of the thymus gland, such as during infancy, can lead to a higher risk of infections, autoimmune conditions (reaction to our own body protein), allergies, and an increased risk of certain cancers.
What are the health conditions associated with the thymus gland?
There are many diseases and disorders that can affect the thymus gland, ranging from genetic disorders that are evident at birth to cancers that are most common in older adults. These disorders can lead to problems with immunity and autoimmunity, such as myasthenia gravis and hypogammaglobulinemia.
- Thymic aplasia or hypoplasia: Aplasia of the thymus is a condition in which the thymus gland does not develop. Hypoplasia means the gland is underdeveloped. It may be seen in a genetic condition called DiGeorge syndrome. Children born with this disorder have significantly reduced or absent thymus function. They have severely reduced immunity and are thus prone to repeated infections besides other health conditions.
- Myasthenia gravis: It is a long-term neuromuscular condition characterized by weakness of the various muscles in the body. Studies have suggested that antibodies triggered by the thymus gland block the communication between the nerves and muscles in myasthenia gravis. This leads to muscle weakness characterized by various symptoms such as difficulty in speaking, chewing, swallowing, drooping of the eyelid, difficulty in walking, and neck holding.
- Thymic follicular hyperplasia: Hyperplasia causes enlargement of the lymphoid follicles (cells of the thymus gland). This may lead to conditions such as lupus, Grave’s disease, and myasthenia gravis where the body attacks its own cells.
- Thymoma: Thymomas are tumors of the thymus gland. They are generally benign (noncancerous) but maybe rarely malignant (cancerous). Tumors of the thymus gland may present with symptoms such as shortness of breath, cough, chest pain, difficulty swallowing, loss of appetite, and unintended weight loss. The tumor may exert pressure on the nearby blood vessels to cause symptoms such as swelling of the face, headache, and dizziness.
- Thymic cysts: A cyst is a fluid-filled swelling. Thymic cysts generally do not produce any symptoms and are incidentally diagnosed. A thymic cyst is usually harmless, but it may be a site of cancer such as thymoma or lymphoma.
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