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Hormones regulate numerous metabolic processes throughout the body. The production of hormones is regulated by a feedback mechanism involving the brain.
When thyroid hormone levels are low, the hypothalamus produces a hormone known as thyrotropin (TRH) that causes the pituitary gland at the base of the brain to release thyroid stimulating hormone (TSH).
TSH stimulates the thyroid gland to release more T4. Since the thyroid gland is controlled by the pituitary gland and hypothalamus, disorders of these tissues can also affect thyroid function.
The most common thyroid problems involve abnormal production of thyroid hormones. Too much thyroid hormone results in hyperthyroidism. Insufficient hormone production leads to hypothyroidism. Thyroid disorders can range from a small, harmless goitre (enlarged gland) that needs no treatment to life-threatening cancer.
Most thyroid problems can be managed well if treated. Hyperthyroidism, particularly Graves’ disease, tends to run in families and is more common in women.
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All types are due to an overproduction of thyroid hormones, but the condition can occur in several ways:
• Graves’ disease: Too much thyroid hormone produced.
• Toxic adenomas: Nodules develop in the thyroid gland and secrete thyroid hormones, upsetting the body’s chemical balance; some goitres contain several nodules.
• Subacute thyroiditis: Inflammation of the thyroid that causes the gland to produce excess hormones, resulting in temporary hyperthyroidism that generally lasts a few weeks.
• Pituitary gland malfunctions or cancerous growths in the thyroid gland: Although rare, hyperthyroidism can also develop from these causes.
• Hypothyroidism: This happens because of underproduction of thyroid hormones. Since energy production requires certain amounts of thyroid hormones, a drop leads to lower energy levels.
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Causes of hypothyroidism include:
• Hashimoto’s thyroiditis: This is an autoimmune disorder in which the body attacks its own thyroid tissue, which eventually dies and stops producing hormones.
• Removal of the thyroid gland: The thyroid may have been surgically removed or chemically destroyed.
• Exposure to excessive amounts of iodide: From cold and sinus medication, the heart medicine amiodarone, or certain contrast dyes given before some X-rays.
• Lithium: This drug used to treat mental illness has also been implicated in hypothyroidism.
• A defective or missing thyroid gland, as seen in newborns. Hypothyroidism is especially dangerous to newborns and infants. A lack of thyroid hormones at an early age can lead to the development of cretinism (mental retardation) and dwarfism (stunted growth). Most infants now have thyroid levels checked routinely after birth.
• Cancer of the thyroid gland: This occurs in about 5% of thyroid nodules. You might have nodules for several years before they become cancerous.
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Hyperthyroidism
The body metabolism speeds up and cause symptoms common to hyperthyroidism when there’s a high level of thyroid hormone in the bloodstream. Symptoms include:
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Hypothyroidism
The symptoms are those associated with a slow metabolism which include:
Each individual may have any number of these symptoms, and they will vary with the severity of the hormone deficiency or excess. Some symptoms appear in both hypothyroidism and hyperthyroidism.
Most people will have a combination of symptoms. If you have any of these symptoms, you need to see your doctor.
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Hyperthyroidism
Untreated this can lead to serious complications, mainly related to the heart. Some heart-related complications are: arrhythmia, increase in the size of the heart cavities, thinning the heart muscle, and congestive heart failure, cardiac arrest and hypertension.
People with Graves’ disease can develop bulging, red or swollen eyes, sensitivity to light, blurring or double vision. Untreated, severe eye problems can lead to vision loss.
Hyperthyroidism also places you at risk of thyrotoxic crisis — a sudden intensification of symptoms, leading to a fever and even delirium.
Hypothyroidism
The pituitary will make additional TSH to entice the thyroid to produce more hormone. This constant overproduction of TSH may cause a goitre. If not treated, hypothyroidism will progress. Rarely, complications can result in heart failure or coma.
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