Hyperthyroidism: when thyroid gland makes too much hormone

Hyperthyroidism is a type of thyrotoxicosis characterized by a metabolic disorder in which excessive thyroid gland activity leads to hypersecretion of the thyroid hormones free thyroxine (T4) or free triiodothyronine (T3), or both, resulting in abnormally elevated plasma levels of these hormones. Hyperthyroidism can be classified as primary (if the condition originates in the thyroid gland) or secondary (if the condition originates in the pituitary gland).

Excess thyroid hormones (TH) induce a global increase in metabolism, elevating energy expenditure, heat production, and oxygen consumption. Protein synthesis increases, but overall, catabolism outweighs anabolism, leading to a negative nitrogen balance. Additionally, tissue sensitivity to catecholamines increases, likely due to enhanced adrenergic receptor activity.

Symptoms of hyperthyroidism often include:

• Nervousness or irritability
• Fatigue
• Muscle weakness
• Heat intolerance
• Difficulty sleeping
• Tremors, usually in the hands
• Irregular or rapid heartbeats
• Frequent bowel movements or diarrhea
• Weight loss
• Mood changes
• Goiter, is an enlargement of the thyroid gland that can make the neck appear swollen, occasionally causing difficulty in breathing or swallowing

Older adults over 60 may experience different symptoms than younger adults, such as loss of appetite or social withdrawal, which may sometimes be mistaken for depression or dementia.

If left untreated, hyperthyroidism can cause serious health problems, including:

• Irregular heartbeats that can lead to blood clots, stroke, heart failure, and other cardiac issues
• Graves’ ophthalmopathy: an eye condition that can cause double vision, light sensitivity, and eye pain, and in rare cases, vision loss
• Bone thinning and osteoporosis
• Fertility problems in women
• Pregnancy complications such as preterm birth, low birth weight, high blood pressure during pregnancy, and miscarriage

The most frequent causes of hyperthyroidism include:

• Graves’ Disease: an autoimmune disorder where the immune system attacks the thyroid, causing it to produce too much hormone. It is the most common cause of primary hyperthyroidism. Graves’ disease is triggered by the production of antibodies against the thyroid-stimulating hormone receptor (anti-TSHR), which overstimulates the thyroid gland, increasing T3 and T4 production
• Thyroid nodules: growths in the thyroid that are typically benign (noncancerous) but can become overactive and produce excess thyroid hormones. These are more common in older adults
• Thyroiditis: inflammation of the thyroid, which causes stored thyroid hormones to leak out of the gland
• Excess iodine: found in some medications, cough syrups, seaweed, and seaweed-based supplements. Consuming too much can cause the thyroid to overproduce hormones
• Excess thyroid medication: this can happen if individuals taking medication for hypothyroidism (underactive thyroid) take too much

• Being female
• Being over 60 years old
• Having been pregnant or given birth within the past six months
• A history of thyroid surgery or thyroid problems such as goiter
• A family history of thyroid disease
• Having pernicious anemia, a condition where the body cannot produce enough healthy red blood cells due to a vitamin B12 deficiency
• Having type 1 diabetes or primary adrenal insufficiency, a hormonal disorder
• Consuming excessive iodine through large amounts of food, medication, or supplements containing iodine

Diagnosis is typically based on:

• The patient’s medical history
• A physical examination
• Testing thyroid-stimulating hormone (TSH), T3, T4, and thyroid antibody levels. In primary hyperthyroidism, free T4 levels are usually elevated while TSH levels are decreased. In secondary hyperthyroidism, both hormones are elevated
• Imaging tests such as a thyroid scan, ultrasound, or radioactive iodine uptake test, which measures how much radioactive iodine the thyroid absorbs from the bloodstream after swallowing a small dose

Treatments for hyperthyroidism include medications, radioactive iodine therapy, and thyroid surgery:

• Antithyroid medications: these reduce the thyroid's hormone production. This is the simplest treatment, though it often does not provide a permanent cure
• Beta-blockers: these help alleviate symptoms such as tremors, rapid heartbeats, and nervousness
• Radioactive iodine therapy: a common and effective treatment for hyperthyroidism, it involves taking radioactive iodine orally, either as a capsule or liquid. This slowly destroys thyroid cells responsible for hormone production. Almost everyone treated with radioactive iodine develops hypothyroidism later, as the hormone-producing cells are destroyed. However, hypothyroidism is easier to manage and causes fewer long-term health problems than hyperthyroidism

Hyperthyroidism cannot be prevented. However, following a healthy lifestyle (doing exercise and following a well-balanced diet) can decrease the risk of developing this condition.