Hyperthyroidism
Hyperthyroidism, also known as overactive thyroid, is a condition where the thyroid gland produces excessive amounts of thyroid hormones, leading to a clinical syndrome characterised by a variety of systemic effects.
Signs and Symptoms
Hyperthyroidism can present with a wide range of symptoms, including irritability, muscle weakness, sleeping problems, fast heartbeat, heat intolerance, and diarrhoea. Patients may also experience weight loss, despite increased appetite, and an enlargement of the thyroid gland (goitre).
In some cases, particularly in the elderly, symptoms might be less pronounced. An uncommon but severe complication is thyroid storm, characterised by extreme symptoms such as high fever, rapid heartbeat, and confusion, which can be fatal if not treated promptly.
Causes
The primary cause of hyperthyroidism is Graves' disease, an autoimmune disorder that accounts for 50-80% of cases. Other causes include multinodular goitre, toxic adenoma, thyroiditis (inflammation of the thyroid), excessive iodine intake, and excessive consumption of synthetic thyroid hormone.
Less commonly, it can be caused by a pituitary adenoma.
Diagnosis
Diagnosis of hyperthyroidism is primarily based on clinical symptoms and confirmed through blood tests. Key blood tests include measurements of thyroid-stimulating hormone (TSH) and the thyroid hormones T3 and T4.
Typically, TSH levels are low, and T3 and T4 levels are elevated. Additional tests, such as radioactive iodine uptake tests and thyroid scans, can help determine the cause.
Measurement of antithyroid autoantibodies, such as those against the TSH receptor, is useful in diagnosing Graves' disease.
Treatment
Treatment for hyperthyroidism depends on the cause and severity of the condition. The main treatment options include:
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Radioiodine Therapy: Involves oral administration of iodine-131, which selectively destroys overactive thyroid tissue over weeks to months. This often leads to hypothyroidism, which is then managed with synthetic thyroid hormone replacement.
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Medications: Beta blockers are used to control symptoms such as rapid heart rate and anxiety. Antithyroid medications like methimazole reduce hormone production.
These medications may be used temporarily until other treatments take effect.
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Surgery: Thyroidectomy, the surgical removal of the thyroid gland, is considered for patients with large goitres, those who cannot tolerate medications, or when cancer is suspected. Post-surgery, patients typically require lifelong thyroid hormone replacement.
Additional Management
- Diet: Patients with autoimmune hyperthyroidism should avoid iodine-rich foods like seaweed.
- Monitoring: Regular follow-ups with blood tests to monitor thyroid function are essential to adjust treatment and manage potential hypothyroidism post-treatment.
Epidemiology
Hyperthyroidism affects about 1.2% of the population in the United States and 2.5% of adults worldwide, occurring more frequently in women. The condition typically presents between the ages of 20 and 50 but can occur at any age.
Hyperthyroidism is associated with increased morbidity if left untreated, primarily due to complications like cardiovascular diseases and osteoporosis.
Special Considerations
Thyroid Storm
Thyroid storm is a life-threatening exacerbation of hyperthyroidism symptoms requiring immediate medical intervention with beta blockers, antithyroid medications, iodine solutions, and steroids.
Pregnancy
During pregnancy, diagnosing hyperthyroidism can be challenging due to elevated thyroid hormone levels in the first trimester. Propylthiouracil is preferred for treatment during the first trimester due to its lower teratogenic risk compared to methimazole.
Research continues to look at more effective treatments and better understanding of the underlying mechanisms of hyperthyroidism to improve patient outcomes.
Self-assessment MCQs (single best answer)
What is the most common cause of hyperthyroidism?
Which symptom is NOT typically associated with hyperthyroidism?
What is the first-line treatment for hyperthyroidism in a non-pregnant adult with no contraindications?
Which blood test result is typically seen in a patient with hyperthyroidism?
What serious complication can arise from untreated hyperthyroidism and is considered a medical emergency?
Which symptom is a characteristic feature of Graves' disease but not typically seen in other forms of hyperthyroidism?
Which medication is used to control symptoms such as rapid heartbeat and anxiety in hyperthyroidism but does not treat the underlying condition?
What is the preferred treatment for hyperthyroidism during the first trimester of pregnancy?
Which diagnostic test is most useful in determining the cause of hyperthyroidism?
In addition to hyperthyroidism, which other condition is commonly associated with Graves' disease?
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