ภาวะต่อมไทรอยด์ทํางานมากเกินไป (ไฮเปอร์ไทรอยด์ Hyperthyroidism)

Hyperthyroidism

Hyperthyroidism occurs when the thyroid gland becomes overactive, and thyroid hormones are excessively produced and released into the body. The metabolic rate increases, leading to myriad symptoms.

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Hyperthyroidism

The thyroid gland's location is in the middle of the neck, between the larynx and the sternum. It makes triiodothyronine (T3) and thyroxine (T4) hormones which regulate the body's metabolism, temperature, heart rate, and protein production.

The pituitary gland at the base of the brain controls and regulates the function of the thyroid gland by secreting thyroid-stimulating hormone (TSH), stimulating the thyroid to produce T3 & T4. If T3 & T4 are insufficient, the pituitary will secrete more TSH and vice versa. 

Hyperthyroidism occurs when the thyroid gland becomes overactive, and thyroid hormones are excessively produced and released into the body. The metabolic rate increases, leading to myriad symptoms.

Symptoms

  • Anxiety and irritability
  • Insomnia
  • Upper arm and thigh muscle weakness
  • Hand tremors 
  • Sweating and heat intolerance
  • Fast or irregular heartbeats
  • Fatigue
  • Sudden loss of weight despite a normal or increased appetite
  • Frequent bowel movements

Some women may experience irregular menstruation, or their periods may suddenly stop. Some men may develop erectile dysfunction or enlarged or tender breasts. These symptoms improve and resolve after hyperthyroidism resolves with treatment. 

Symptoms such as irregular heartbeat, weight loss, depression, tiredness, and fatigue while doing daily activities can occur unnoticeably in older adults. You should see a doctor for a proper diagnosis to pinpoint the root cause of those symptoms.

Causes

When the thyroid gland produces and releases excessive thyroid hormones, hyperthyroidism ensues. Medical conditions that affect the function of the thyroid gland include:

  • Graves' disease, an autoimmune disease, is the most common cause of hyperthyroidism. The thyroid gland is stimulated by autoantibodies made by the immune system, leading to excessive thyroid hormone production. 
  • Toxic adenoma, toxic multinodular goiter, or Plummer disease occurs when a thyroid adenoma produces thyroid hormone more than necessary. The thyroid usually is enlarged. 
  • Subacute thyroiditis  (Subacute granulomatous thyroiditis or de Quervain's thyroiditis) results from a viral infection, leading to a painful and enlarged thyroid gland. After the condition subsides, you may develop hypothyroidism for months. There is evidence that COVID-19 is related to subacute thyroiditis.
  • Postpartum thyroiditis (Silent thyroiditis) causes temporary inflammation of the thyroid. A few months after childbirth, you may develop painless postpartum thyroiditis lasting for several months, followed by hypothyroidism. You may experience muscle cramps, fatigue, and weight gain.  
  • Excessive use of thyroid hormone medication to treat hypothyroidism can increase the level of thyroid hormones as high as those in people with hyperthyroidism.

Risk factors

  • You have a close family member with thyroid or autoimmune thyroid diseases, such as Graves' disease.
  • You have chronic disorders such as pernicious anemia and primary adrenal insufficiency.
  • You had childbirth recently. 

Complications

  • Heart diseases such as atrial fibrillation or congestive heart failure
  • Osteoporosis may occur because the high level of thyroid hormones impedes calcium absorption, making the bones weak and brittle.
  • Thyroid eye disease is a disorder of eye muscles and tissues. It usually affects people with hyperthyroidism who also smoke. Vision problems caused by thyroid eye disease are:
    • Protruding eyeballs
    • Eye pain
    • Pressure in the eyes
    • Gritty eyes
    • Puffy eyelids
    • Redness in the eyes
    • Double vision
    • Sensitive to light
    • Vision loss
  • Graves' dermopathy can cause skin color change and swelling on the shins and feet. However, this is rare and only occurs in people with Graves' disease.
  • Thyrotoxic crisis or thyroid stormis a rare condition that can be life-threatening, with symptoms of
    • Fever
      • Rapid heartbeat
      • Nausea and vomiting
      • Dehydration
      • Diarrhea
      • Confusion
      • Delirium
      • Confusion
      • Delirium

    Diagnosis

    • Blood testing to measure thyroid hormones and thyroid-stimulating hormone (TSH) levels. If the thyroid hormone levels are high whereas the TSH is low, your doctor may order a thyroid scan or a test for thyroid antibodies to help differentiate the cause of your condition. They could arise from thyroiditis, Graves' disease, or toxic nodular goiter.



    Treatment

    The most suitable treatment depends on your age and the type and severity of your condition. You can discuss the pros and cons of each treatment option with your doctor.

    Medications

    • Antithyroid drugs, including methimazole and propylthiouracil, can decrease thyroid hormone production. If you are pregnant, your doctor may recommend methimazole instead of propylthiouracil. Discuss the side effects of the medications with your doctor before taking them.
    • Beta blockers, such as atenolol or propranolol, help control hyperthyroidism symptoms of fast heart rate, anxiety, shakiness, and heat intolerance.

    Radioiodine

    You will take radioiodine capsules or liquid forms once. Radioiodine requires 6-18 weeks to ablate thyroid tissues permanently and decrease thyroid hormone production. Usually, your doctor will prescribe an antithyroid drug as the first treatment, especially if you are an older adult or have severe heart disease. After radioiodine treatment, you must take thyroid hormone replacement for the rest of your life.

    The risks of radioiodine include:

    • Recurrent hyperthyroidism, particularly in those with severe hyperthyroidism or huge goiter
    • Worsened eye disease, compared to people who have surgery. 
    • Risk of exposing people around you to radiation. Keep a distance from young children and pregnant women for 5-7 days after treatment. 
    • Hypothyroidism.

    Surgery

    Surgery provides a permanent cure for hyperthyroidism, but there are risks as follows:

    • Injury during surgery to recurrent laryngeal nerve, which causes hoarse voice, and to parathyroid glands, which help maintain the balance of calcium levels in the body.
    • Hypothyroidism develops in almost everyone who has the thyroid removed. 
    • Your doctor may recommend surgical removal if:
    • It is difficult for you to breathe because a large goiter blocks the airways.
    • You have a precancerous nodule in the thyroid gland. 
    • You develop Graves' eye disease.
    • You want definitive treatment before getting pregnant. 
    • Antithyroid drugs do not improve your symptoms, and you do not want to use radioiodine.

    Lifestyle modifications and home remedies

    If you have hyperthyroidism, getting treatment is crucial. At home, you can cope with your condition by:

    • Regular exercise to strengthen your muscles, heart, and lungs. It helps you feel active and energetic. 
    • Practice relaxation techniques because stress can aggravate your condition, particularly hyperthyroidism caused by Graves' disease.  

    Pregnancy and hyperthyroidism

    If you have hyperthyroidism and plan to have a baby, you should discuss the possibilities with your doctor. Untreated hyperthyroidism in mothers can affect the development of the fetus. Watchful monitoring and medication adjustment can help avoid the risks. 

    If you do not want to take the antithyroid drugs, you may consider having your thyroid removed or radioiodine treatment before the pregnancy. However, at least six months must have elapsed after radioiodine treatment before your pregnancy.

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      Published: 03 Apr 2023

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