Hyperthyroidism is a condition characterized by an overactive thyroid gland that produces excess thyroid hormones. This can accelerate the body’s metabolism and cause a number of symptoms. Hyperthyroidism can occur at any age, but there are peak ages at which it is more likely to develop.
What is Hyperthyroidism?
The thyroid gland is a small, butterfly-shaped gland located at the base of the neck. It produces two main hormones – triiodothyronine (T3) and thyroxine (T4). These hormones regulate the body’s metabolism, heart rate, blood pressure, body temperature and weight.
In hyperthyroidism, the thyroid gland becomes overactive and produces more thyroid hormones than the body needs. This speeds up the metabolism, causing a number of symptoms:
- Unexplained weight loss
- Rapid heartbeat
- Trembling hands
- Sweating
- Increased appetite
- Fatigue
- Muscle weakness
- Hair loss
- Sleep problems
- Irregular menstrual cycles
If left untreated, hyperthyroidism can lead to more serious complications like heart problems and brittle bones. That’s why it’s important to get an accurate diagnosis and treatment.
Causes of Hyperthyroidism
There are several possible causes of hyperthyroidism:
- Graves’ disease: The most common cause of hyperthyroidism (about 70% of cases), an autoimmune disorder where antibodies stimulate the thyroid to secrete excessive hormones.
- Toxic nodules: Benign lumps or nodules develop in the thyroid and secrete excess thyroid hormone, found in about 3% of cases.
- Toxic multinodular goiter: Multiple nodules in the thyroid produce excess thyroid hormone, estimated to cause about 4% of hyperthyroidism cases.
- Thyroiditis: Inflammation of the thyroid causes excess hormone release into the bloodstream. Several types like subacute thyroiditis or postpartum thyroiditis can cause temporary hyperthyroidism.
- Excess iodine: Consuming foods or supplements with very high levels of iodine can trigger hyperthyroidism in some people.
- Medications: The drug amiodarone, used to treat heart rhythm disorders, can damage the thyroid and cause it to release thyroid hormone.
Who Gets Hyperthyroidism?
Hyperthyroidism affects about 1% of Americans. Women are up to 10 times more likely to develop hyperthyroidism than men. It can occur at any age, but there are peak ages where it is more commonly diagnosed:
- Ages 20-40: This accounts for the majority of hyperthyroidism cases. It is typically caused by Graves’ disease and peaks between ages 25-30.
- Over age 60: The prevalence rises again in older adulthood, usually due to toxic nodules or multinodular goiter.
- After pregnancy: Hyperthyroidism can occur in the postpartum period, a condition called postpartum thyroiditis that causes temporary hyperthyroidism followed by hypothyroidism.
Those with a family history of thyroid disorders or other autoimmune diseases like type 1 diabetes have an increased risk. Hyperthyroidism is also more common in those with existing thyroid issues like nodules, goiter or thyroiditis.
Diagnosing Hyperthyroidism
If hyperthyroidism is suspected based on symptoms, a doctor will order blood tests to confirm the diagnosis by detecting elevated levels of thyroid hormones. Common lab tests include:
- TSH (thyroid-stimulating hormone) level: This will be low, as the pituitary responds to high thyroid hormone levels by decreasing TSH production.
- Free T4 and Free T3: Levels of circulating free thyroid hormones will be elevated.
- Thyroid antibody tests: Presence of antibodies like thyroid peroxidase (TPO) and thyrotropin receptor (TRAb) antibodies indicate autoimmune hyperthyroidism.
Imaging studies like thyroid ultrasound or radioactive iodine uptake scans may also be done to evaluate the cause and look for nodules or inflammation.
Treating Hyperthyroidism
There are several treatment options for hyperthyroidism, including:
- Antithyroid medications: Drugs like methimazole and propylthiouracil block thyroid hormone production. They are often used as initial short-term treatment to control hyperthyroidism.
- Radioactive iodine therapy: Taking a dose of radioactive iodine damages thyroid cells and prevents excess hormone production. It is very effective but causes permanent hypothyroidism requiring daily thyroid hormone replacement.
- Surgery: Removing part or all of the thyroid gland controls excess hormone production. This may be recommended if antithyroid medications are ineffective or a patient cannot tolerate them.
- Beta-blockers: Medications that block the effects of thyroid hormones on the body may be used to control symptoms like rapid heart rate.
The treatment selected depends on the underlying cause, severity of hyperthyroidism, patient age, and other factors. Many patients eventually require lifelong thyroid hormone replacement medication.
Hyperthyroidism in Young Adults
Young adulthood, defined roughly as ages 20-40, is the most common time for hyperthyroidism to develop. Up to 70% of diagnoses occur within this age range. Some key points about hyperthyroidism in young adults:
- Graves’ disease is the cause in over half of cases.
- Women are affected up to 10 times more than men.
- Symptoms like unexplained weight loss, fatigue, palpitations and anxiety may disrupt college, careers and relationships.
- Seeking early treatment can prevent complications of untreated hyperthyroidism.
- Antithyroid medications are often the first-line treatment for young adults to avoid permanent hypothyroidism after radioactive iodine therapy or surgery.
- Treatment aims to control symptoms and prevent long-term thyroid damage until the hyperthyroidism goes into remission.
With proper treatment, the prognosis for young adults with hyperthyroidism is good. The earlier it is controlled, the lower the risk of lasting effects on thyroid function.
Hyperthyroidism in Middle Age
Middle age is generally defined as ages 40-60. The pattern of hyperthyroidism diagnoses starts to shift in this population:
- Toxic nodules become a more common cause than Graves’ disease.
- There is a higher incidence of toxic multinodular goiter.
- There is often a history of thyroid nodules or goiter leading up to hyperthyroidism.
- Hyperthyroidism may be triggered by high iodine intake from foods or supplements.
- Subacute thyroiditis causing transient hyperthyroidism is more common.
Treatment considerations for middle-aged patients with hyperthyroidism include:
- Antithyroid drugs may not be effective long-term if toxic nodules or goiter are present.
- Radioactive iodine therapy becomes a more likely treatment to permanently destroy overactive thyroid tissue.
- Surgery like thyroid lobectomy may be an option for localized nodules or goiter causing hyperthyroidism.
- Identifying dietary or medicinal sources of excess iodine intake should be done.
With appropriate treatment tailored to the cause and clinical situation, patients can achieve good control of hyperthyroidism. Careful monitoring is needed for potential hypothyroidism requiring hormone replacement.
Hyperthyroidism in Older Adults
In older adulthood, defined as over 60 years old, the causes and treatment approach to hyperthyroidism change further:
- Toxic multinodular goiter becomes the most common cause of hyperthyroidism.
- Up to 10% of overt hyperthyroidism cases in the elderly are due to thyroiditis.
- Iodine excess continues to be a potential trigger.
- Symptoms like fatigue, weight loss and cardiac arrhythmias may go unrecognized as normal aging changes.
- Antithyroid drugs carry increased risks like liver damage in older patients.
- Surgery may not be advisable in older patients with additional health issues.
Key considerations for the management of hyperthyroidism in patients over 60 include:
- Careful diagnosis is needed, as TSH levels may be less reliable in indicating hyperthyroidism.
- Underlying cardiovascular diseases increase risks from uncontrolled hyperthyroidism.
- Radioactive iodine therapy is often the treatment of choice due to its effectiveness and safety profile.
- Beta-blockers are important to minimize hyperthyroidism symptoms.
- Overtreating and inducing hypothyroidism should be avoided.
- Monitoring and medication adjustment following radioactive iodine is crucial.
When individually tailored to the patient’s health status, radioactive iodine can safely treat hyperthyroidism in older adults and allow for close monitoring and prevention of complications.
Risk Factors for Developing Hyperthyroidism
While hyperthyroidism can happen to anyone, certain factors increase the risk of developing overactive thyroid:
- Sex: Women are up to 10 times more susceptible to hyperthyroidism.
- Age: Most common in the 20-40 and over 60 age ranges.
- Family history: Having a parent, sibling or child with Graves’ disease increases risk up to 28 times.
- Thyroid disease history: Previous bouts of thyroiditis, nodules or goiter raise the risk of future overactive thyroid.
- Other autoimmune conditions: Those with lupus, rheumatoid arthritis, type 1 diabetes or pernicious anemia have a higher rate of hyperthyroidism.
- Pregnancy: Hyperthyroidism occurs in about 0.1-0.4% of pregnancies, often manifesting in the first trimester.
- High iodine intake: Consuming unusually high levels of iodine through foods like seaweed or supplements can trigger hyperthyroidism.
- Medications: Drugs like amiodarone, interleukin-2 and lithium may impact thyroid function.
Being aware of these risk factors can help identify individuals who should be screened for thyroid dysfunction and monitored for signs of hyperthyroidism.
Prevention of Hyperthyroidism
There is no definitive way to prevent hyperthyroidism, but some strategies may lower the chances of developing overactive thyroid:
- Avoid very high iodine intake from foods like kelp or supplements containing iodine.
- Be cautious with amiodarone and limit use to essential cases, as it can damage the thyroid.
- Treat underlying autoimmune conditions to try to prevent the immune system from attacking the thyroid.
- Monitor thyroid function for those on lithium therapy for bipolar disorder.
- Women with autoimmune diseases planning pregnancy may consider levothyroxine to lower TSH as some evidence indicates this may reduce the risk of postpartum thyroiditis.
However, many causes like Graves’ disease, toxic nodules and thyroiditis cannot be prevented outright. For those predisposed, focusing on routine screening and early detection offers the best opportunity for prompt diagnosis and treatment.
Hyperthyroidism in Pregnancy
Thyroid conditions are common in pregnancy, estimated to affect 2-5% of expecting mothers. Hyperthyroidism occurs in about 0.1-0.4% of pregnancies. Some key facts about hyperthyroidism in pregnancy:
- Graves’ disease is the most common cause. Other potential causes include toxic nodules and gestational transient thyrotoxicosis.
- Symptoms like fatigue, weight loss and heart palpitations may be attributed to normal pregnancy changes if not recognized.
- Hyperthyroidism increases the risk of miscarriage, preeclampsia, preterm birth, low infant birth weight and stillbirth.
- Neonatal hyperthyroidism can temporarily affect infants born to mothers with uncontrolled hyperthyroidism.
- Methimazole is the preferred antithyroid drug for treating hyperthyroidism during pregnancy.
- Radioactive iodine therapy is contraindicated during pregnancy and breastfeeding.
Careful monitoring of thyroid function is needed throughout pregnancy to maintain normal thyroid hormone levels and prevent complications. Postpartum screening is also recommended as postpartum thyroiditis occurs in 5-10% of women.
Signs of Hyperthyroidism in Cats
Feline hyperthyroidism is a common endocrine disorder in middle-aged and older cats. Some signs of hyperthyroidism in cats include:
- Weight loss despite increased appetite
- Anxiety or restless behavior
- Vomiting or diarrhea
- Increased thirst and urination
- Poor and unkempt coat
- Panting
- Rapid heart rate
- Enlarged thyroid glands in the neck that can be felt as firm nodules
Diagnosis is made through physical exam, palpating enlarged thyroid glands, and measuring elevated T4 hormone levels on a blood test. Radioactive iodine therapy is the gold standard treatment, but medications and special diet can also be used to manage feline hyperthyroidism.
Conclusion
In summary, hyperthyroidism can develop at different ages due to various causes. Graves’ disease typically affects younger adults while toxic nodules become more common with age. Women have a higher prevalence overall. Diagnosis is made by testing thyroid hormone levels. Treatment depends on the cause and patient factors, but commonly includes antithyroid medications, radioactive iodine therapy or surgery. Careful monitoring and screenings can help detect hyperthyroidism early for optimal management.