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Hyperthyroidism
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Endocrine System

Hyperthyroidism

Hyperthyroidism, or overactive thyroid, occurs when the thyroid gland produces an excess of hormones, impacting vital functions like heart rate, metabolism, and mood.

Overview

The thyroid is a small, butterfly-shaped gland located in the front of the neck. It produces hormones that control how the body uses energy. These hormones influence nearly every organ, affecting breathing, heart rate, weight, digestion, and moods. If left untreated, hyperthyroidism can lead to serious complications involving the heart, bones, muscles, menstrual cycle, and fertility.

Causes

Hyperthyroidism can be triggered by several factors:

  • Graves' disease: An autoimmune disorder where the immune system attacks the thyroid, causing it to overproduce hormones.
  • Thyroid nodules: Benign growths on the thyroid that may become overactive.
  • Thyroiditis: Inflammation of the thyroid that causes stored hormones to leak into the bloodstream.
  • Excess iodine: Found in certain medicines, cough syrups, and seaweed supplements.
  • Excess thyroid medicine: Occurs when doses for hypothyroidism are too high.

Risk Factors

You may be at higher risk if you:

  • Are a woman
  • Are older than age 60
  • Have been pregnant or had a baby within the past 6 months
  • Have a history of thyroid surgery or problems like goiter
  • Have a family history of thyroid disease
  • Have pernicious anemia, type 1 diabetes, or primary adrenal insufficiency
  • Consume excessive amounts of iodine

Symptoms

Symptoms vary by individual and may include:

  • Nervousness, irritability, or mood swings
  • Fatigue and muscle weakness
  • Trouble tolerating heat and difficulty sleeping
  • Tremors, usually in the hands
  • Rapid or irregular heartbeat
  • Frequent bowel movements or diarrhea
  • Weight loss
  • Goiter: An enlarged thyroid that may cause neck swelling and difficulty breathing or swallowing.

Note: Adults over 60 may experience different symptoms, such as loss of appetite or social withdrawal, which can be mistaken for depression or dementia.

Complications

Untreated hyperthyroidism can lead to:

  • Irregular heartbeat, potentially causing blood clots, stroke, or heart failure
  • Graves' ophthalmopathy: An eye disease causing double vision, light sensitivity, and pain
  • Thinning bones and osteoporosis
  • Fertility issues and pregnancy complications

Diagnosis

Providers diagnose the condition using:

  • Medical history and physical exam
  • Thyroid tests: Including TSH, T3, T4, and thyroid antibody blood tests
  • Imaging tests: Thyroid scan, ultrasound, or a radioactive iodine uptake test

Treatment & Management

  • Medicines: Antithyroid drugs to reduce hormone production or beta blockers to manage symptoms like tremors and rapid heart rate.
  • Radioiodine therapy: A capsule or liquid that destroys overactive thyroid cells. This often leads to hypothyroidism, which is easier to manage.
  • Surgery: Removal of part or all of the thyroid, typically reserved for large goiters or cases where medication is not an option.

Patients should consult their provider regarding the management of iodine intake through food, supplements, and medications.

Frequently Asked Questions

Look for a rapid, pounding heartbeat (palpitations) that feels irregular, new or worsening chest pain, shortness of breath, severe tremors, sudden confusion or agitation, or a fever with a fast heart rate (possible thyroid storm). If any of these appear, call emergency services right away.
Most people feel a gradual improvement in symptoms over 4–8 weeks, though fatigue and a temporary increase in thyroid hormone levels (post‑RAI flare) can occur. Common side effects include neck tenderness, mild nausea, and temporary worsening of hyperthyroid symptoms. About 6–12 months after RAI, many patients develop hypothyroidism and will need lifelong levothyroxine replacement. Regular blood tests every 6–8 weeks initially help guide dosing.
Yes, many women successfully conceive while on antithyroid drugs (methimazole or propylthiouracil). Your endocrinologist will aim for a low‑normal thyroid hormone level before conception and will check thyroid function every 4–6 weeks throughout pregnancy. Dosage adjustments are common, and the baby’s thyroid status is monitored via ultrasound and newborn screening.
im for a balanced diet rich in whole grains, fruits, vegetables, and lean protein. Limit high‑iodine foods such as seaweed, kelp, and iodine‑fortified salt, especially if you are on antithyroid drugs. Reduce caffeine (coffee, tea, energy drinks, chocolate) because it can worsen tremor, anxiety, and heart palpitations. Staying hydrated and avoiding excessive sugar can also help stabilize energy levels.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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