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Thyroid hormones are essential for the body to function normally. To achieve this purpose, the thyroid hormones must be present in the body in the correct amount -- not too little and not too much.
Hyperthyroidism is the medical term applied to an over-active thyroid gland with consequent excess secretion of thyroid hormones (T3 and T4), causing the body to “speed up.” Hyperthyroidism with an enlarged thyroid gland is more popularly known as toxic goiter.
What are the causes of hyperthyroidism?
Graves' disease is an autoimmune disorder and is the most common cause of hyperthyroidism. The thyroid gland is diffusely enlarged and patients usually complain of eye discomfort or, in extreme cases, bulging eyes. This is most commonly seen among young females and affects multiple family members.
A toxic nodule is a single nodule or lump in the thyroid gland that over-produces hormones, causing hyperthyroidism. Unlike Graves' disease, this is not familial. It is also known as Plummer's nodule.
Toxic multinodular goiter is usually seen in patients more than 50 years old who had long-standing goiters. Unlike Plummer's nodule, several nodules may hyperfunction in this condition.
Acute or subacute thyroiditis presents with an antecedent viral infection with thyroid gland enlargement, later developing symptoms of hyperthyroidism because of leakage of thyroid hormones in the bloodstream. Fortunately, this condition resolves spontaneously, but may later cause hypothyroidism.
Overmedication of thyroid hormones given for hypothyroidism, thyroid nodules or thyroid cancer can produce “thyrotoxicosis factitia.”
What are the common symptoms of hyperthyroidism?
When hyperthyroidism develops, a goiter (enlargement of the thyroid) is usually present and may be associated with some or all of the following symptoms:
- rapid heartbeat
- nervousness or irritability
- shakiness or tremors
- intolerance to heat
- weight loss
- inability to sleep
- muscle weakness
- increased sweating
- shorter menstrual blood flow
How is hyperthyroidism diagnosed?
Hyperthyroidism is diagnosed with blood tests such as thyroid stimulating hormone (TSH), tri-iodothyronine (T3) or tetra-iodothyronine (T4) levels. A low TSH level is the most accurate indicator of hyperthyroidism. If the TSH level is low, it is important to check the thyroid hormone level (high T3 and T4) to confirm the diagnosis of hyperthyroidism.
Radioactive iodine uptake may also be used to diagnose hyperthyroidism. It is a measurement of how much iodine the thyroid gland can collect. A thyroid scan shows how the iodine is distributed throughout the gland. This information is useful in determining the cause of hyperthyroidism.
How is hyperthyroidism treated?
Treatment of hyperthyroidism aims at stopping the overproduction of thyroid hormones. Anti-thyroid medications like PTU, carbimazole or methimazole are used to block the production of thyroid hormones. A rare side effect of these medications is a decrease in the number of white blood cells. A patient who develops a fever while on these medicines must immediately seek medical attention.
Radioactive iodine may be given to destroy thyroid cells. This can kill too many cells causing hormone levels to become low, leading to hypothyroidism.
Surgery removes part or all of the hyperfunctioning thyroid gland. This is the preferred method of treating a toxic nodule.
Excerpt from The Thyroid Gland: Hyperthyroidism by the Philippine Society of Endocrinology and Metabolism.