Hyperthyroidism is a condition caused by an overactive thyroid. The organ produces more hormones than needed, disrupting normal bodily functions like metabolism, body temperature, and pulse rate.
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The thyroid is a butterfly-shaped gland found at the back of your neck. It creates and releases hormones that control your metabolism and heart rate and regulate your body temperature. You can consider the thyroid as the organ that ensures your body operates in a state of balance.
When the thyroid produces too much or too little of the TSH, it throws off an imbalance that leads to various disorders, including:
The triiodothyronine (T3) and thyroxine (T4) hormones are responsible for bringing a state of homeostasis. When these hormones are produced in excess, it results in hyperthyroidism.
A third hormone, the TSH, is made from the brain's pituitary gland and sent to the thyroid to regulate T3 and T4 levels.
Doctors usually do a blood test to check all three hormone levels as it can help determine the cause of hyperthyroidism.
Hyperthyroidism causes an imbalance that you may feel in different body parts. The symptoms vary from one person to another, with some symptoms being more common than others.
These symptoms may include:
Swollen neck characterized by trouble breathing or swallowing (goiter)
Bulging eyes (Graves’ disease)
Irregular menstrual periods
Diarrhea and increased bowel movements
Insensitivity to heat and increased sweating
Body tremors and shaking
Because some of the symptoms are consistent with other medical conditions, people who experience these need to visit a qualified health practitioner for proper diagnosis.
Nearly 80% of diagnosed hyperthyroidism can be attributed to Graves’ disease.¹ When you have this condition, your body's immune system attacks the thyroid gland, forcing it to compensate by producing more thyroid hormones.
Research suggests² that Graves’ disease is a hereditary condition and more prevalent in women.
Thyroiditis is an inflammation of the thyroid gland. It causes the organ to produce excessive hormones, leading to hyperthyroidism. There are two common forms of inflammation:
Subacute thyroiditis, which is caused by a viral infection; and
Postpartum thyroiditis, which can occur one to two months after giving birth.
A toxic nodule (toxic multinodular goiter, if there're many) is a lump that grows out of the thyroid gland and produces hormones without TSH intervention. It leads to hyperthyroidism if the hormones are more than what the body needs.
Thyroid hormone production relies on iodine synthesis by the thyroid gland. However, excessive intake through iodine-rich diets or medication can cause overproduction of the hormone.
People taking hormone supplements to treat hypothyroidism may develop hyperthyroidism. A medical practitioner should always prescribe thyroid hormone replacement, and any changes in prescription should be guided by thorough testing.
The following are more at risk of developing hyperthyroidism:
The elderly (those over age 60)
People with autoimmune conditions, for example, Type 1 diabetes
People with a prior history of thyroid-related conditions like goiter
Family history of thyroid disease or autoimmune disorders
Most people with hyperthyroidism usually get well with proper treatment. Severe conditions might require surgical removal of the thyroid gland. This surgery requires people to be placed on permanent thyroid hormone replacement therapy because the body still needs the thyroid to function.
Hyperthyroidism requires immediate medical diagnosis and treatment. Failure to treat it on time causes severe health complications.
Cardiac problems: Overproduction of thyroid hormones keeps the heart working in overdrive. Untreated hyperthyroidism might cause a stroke or congestive heart failure.
Osteoporosis: Hyperthyroidism interferes with calcium and phosphorus absorption. The absence of these minerals weakens the bones and makes them prone to fractures.
Thyroid storm: A thyrotoxic crisis is a rare but life-threatening condition characterized by excessive metabolic activity. Patients might experience fever, hypertension, nerve-related complications, and tachycardia.
High levels of T3 and T4 in the bloodstream might indicate the presence of hyperthyroidism. The excessive levels trigger a negative feedback loop to the pituitary gland, halting the release of TSH to stop the thyroid gland from producing T3 and T4. And if the TSH levels are too high, the thyroid synthesizes more T3 and T4.
The feedback system is destroyed when either the pituitary gland or the thyroid gland is damaged or if there is another source of T3 and T4 that is not responsive to TSH.
In other words, the thyroid may continue to overproduce despite TSH levels being undetectable.
In rare conditions, hyperthyroidism may be due to an overproduction of TSH by the pituitary gland, causing overstimulation and production of T3 and T4.
The normal range for TSH is between 0.35 mIU/mL and 4.50 mIU/mL. However, some experts agree that the ideal range should be between 0.5 mIU/mL and 2.50 mIU/mL.³
The specified normal range may depend on certain demographics such as age, race, gender, and medical condition.
For instance, a study by the National Health and Nutrition Examination Survey (NHANES)⁴ showed varying upper limits for different age groups:
The optimal range for each person may vary. You should be guided by an endocrinologist after proper diagnosis.
A blood sample can be tested for T3 and T4 hormones, where high levels signal hyperthyroidism. A TSH level will be done at the same time to try and determine the cause of the high thyroid hormone.
Thyroid antibody tests help to diagnose autoimmune thyroid disorders. Other tests might include:
Radioactive iodine uptake test
Biopsy (for suspected cancerous nodules)
The following factors can affect TSH levels:
Illness: Diseases of the endocrine system such as Type 1 diabetes might upset TSH levels in the body.
Pregnancy: TSH levels usually drop during pregnancy.
Medication: Anti-inflammatory medications like ibuprofen can cause a TSH imbalance.
Nutrition: Food rich in iodine may cause TSH levels to rise.
Insomnia: Poor sleeping habits may lead to hormonal imbalance.
Antithyroid medications are usually prescribed to stop excessive hormone production. The dosage is reduced gradually as the symptoms improve.
Radioactive iodine is given in low doses to destroy some of the cells in the thyroid gland, reducing hormone production.
A thyroidectomy is usually prescribed as a last resort. It entails partial or permanent removal of the thyroid gland.
Getting diagnosed with hyperthyroidism can be a nerve-wracking experience. Fortunately, the condition is treatable.
Even though the symptoms and certain risk factors might signal its presence, hyperthyroidism is not one of those conditions you can self-diagnose. Contact your healthcare provider for further tests.
National health and nutrition examination survey III thyroid-stimulating hHormone (TSH)-thyroperoxidase antibody relationships demonstrate that TSH upper reference limits may be skewed by occult thyroid dysfunction (2007)