Majority of the hyperthyroidism conditions are caused by Graves’
disease which accounts for 80% of the hyperthyroidism cases.
Graves' disease can be distinctively identified by lumpy neck and protruding eyes (if you remember that pair of eyes on our very first post). It is an autoimmune disease where the immune system makes antibody called thyroid stimulating immunoglobulin (TSI). These antibodies mimics the function of TSH to stimulate the thyroid to make thyroid hormone excessively.
So what about the other 20%? Other causes will include the following:
Abnormal secretion of TSH
Presence of tumour in the pituitary gland may result in the
secretion of high level of TSH. This leads to excessive signalling of thyroid
hormone production by the thyroid gland.
Temporary Thyroiditis
Following viral infections or pregnancies, some people will
have inflammatory reaction in their thyroid glands known as thyroiditis. Inflammation
of the thyroid gland causes it to become “leaky”, so the amount of thyroid
hormone entering the blood will increase.
Over-consumption of Iodine
The thyroid gland uses iodine to make thyroid hormones.
Taking certain medications, such as amiodarone, food that has high-iodine
content, or supplements that contain higher-than-recommended daily allowances of
iodine, can induce hyperthyroidism.
Hot nodules
Thyroid nodules are tumor-like growths that can develop
within the thyroid gland. Most of these nodules do not affect thyroid hormone
levels but a fraction of them can be presented as “hot nodules”. These hot
nodules have the ability to mimic the thyroid gland tissue which will absorb
the iodine coming into the body, resulting in the production of thyroid
hormones. Additional thyroid hormone production causes the levels to become
abnormally high.
Up next will be the effects of Hyperthyroidism.
References
The Best Darn Hyperthyroidism Book!: Studies on the Overactive Thyroid Gland
By James M. Lowrance
Thyroid For Dummies, 2nd Edition
By Alan L. Rubin, MD
http://www.medicinenet.com/hyperthyroidism/page4.htm#what_causes_hyperthyroidism
http://www.endocrine.niddk.nih.gov/pubs/Hyperthyroidism/#symptoms