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Main > Specialty Areas > Endocrinology >
Causes of Hyperthyroidism
Besides the Graves' Disease (see previous page), other causes of Hyperthyroidism include:
Functioning Adenoma and Toxic Multinodular Goiter
The thyroid gland becomes lumpier as we get older. In the majority of cases, these lumps are harmless, occasionally, a nodule may become "autonomous," which means that it does not respond to pituitary regulation via TSH and produces thyroid hormones independently.
When there is a single nodule that is independently producing thyroid hormones, it is called a functioning nodule. If there is more than one functioning nodule, the term toxic, multinodular goiter is used. Functioning nodules may be readily detected with a Thyroid Scan.
Hyperthyroidism due to excessive intake of Thyroid Hormones
Taking too much thyroid hormone medication has become very common. Due to the lack of follow-up of patients taking their thryroid medicine, excessive doses of thyroid hormones frequently go undetected. Other persons may be abusing the drug in an attempt to achieve other goals such as weight loss. These patients can be identified by having a low uptake of radioactively-labelled iodine radio iodine on thyroid scan.
Abnormal secretion of TSH as cause of Hyperthyroidism
A tumor in the pituitary gland may produce an abnormally high secretion of TSH, which can lead to excessive signaling to the thyroid gland to produce thyroid hormones. This condition is very rare and can be associated with other abnormalities of the pituitary gland. To identify this disorder, elaborate tests need to be performed to assess the release of TSH.
Thyroiditis's association with hyperthyroidism
Inflammation of the thyroid gland may occur after a viral illness (subacute thyroiditis). This condition is association with
a fever and a painful sore throat.
The thyroid gland is also tender to touch.
Generalized neck aches and pains.
Inflammation of the gland with an accumulation of white blood cells known as lymphocytes may also occur.
In both of these conditions, the inflammation leaves the thyroid gland "leaky," so that the amount of thyroid hormone entering the blood is increased. Lymphocytic thyroiditis is most common after a pregnancy and can actually occur in up to 8% of women after delivery. In these cases, the hyperthyroid phase can last from 4 to 12 weeks and is often followed by a hypothyroid (low thyroid output) phase that can last for up to 6 months. The majority of affected women return to a state of normal thyroid function. Thyroiditis can be diagnosed by a thyroid scan.
Excessive iodine intake
An excess of iodine may cause hyperthyroidism. Iodine-induced hyperthyroidism is usually seen in patients who already have an underlying abnormal thyroid gland. Certain medications, such as Cordarone, which is used in the treatment of heart problems, contain a large amount of iodine and may be associated with thyroid function abnormalities.
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