The Thyroid

The thyroid gland is the “master controller” of metabolism.

About Hyperthyroidism

Hyperthyroidism, or an overactive thyroid, is when the gland produces and releases too much thyroid hormone into the bloodstream, speeding up the body’s metabolism.1 Hyperthyroidism tends to run in families, occurring most commonly in young women.1 Worryingly, little is known about why specific individuals get this condition.1

If you suffer from hyperthyroidism then you are likely to notice you have lost weight, even if you are eating normally or even more than before.1 You may also feel a fast heart rate.1

Key symptoms of hyperthyroidism

Watch out for the following symptoms:1,2

  • Fast heart rate (often more than 100 beats per minute)
  • Nervousness and/or irritability
  • Weight loss without dietary changes
  • Prominent, staring eyes (typical for Graves’ disease)
  • Muscle weakness, especially of the upper arms and thighs
  • Increased sweating
  • Frequent bowel movements
  • Lighter or less frequent menstrual periods
  • Trembling hands
  • Fine brittle hair
  • Smooth and thin skin

It is important that symptoms of hyperthyroidism are not left untreated as serious complications can occur. In addition, hyperthyroidism increases the risk for osteoporosis (loss of bone mass) and bone fractures, with women who have gone through menopause having an even greater risk.4

Symptoms alone do not reliably tell whether you have hyperthyroidism; physical examinations and blood tests are needed.

Who is at risk?

  • Being female 6
  • The elderly generation6
  • People who have relatives with autoimmune disorders6
  • People with autoimmune diseases such as type 1 diabetes 6
  • People with a history of thyroid problems, like goiters 6
  • Patients who have undergone thyroid surgery6

Diagnosing thyroid dysfunction

Thyroid dysfunction can be confirmed by your doctor through a simple blood test to check the level of thyroid-stimulating hormone (TSH) and thyroid hormones in your blood.1

If you are concerned that you could be suffering from problems with your thyroid gland, please discuss this with your doctor. To aid your consultation download our Wellbeing Diary to help you keep a check of the symptoms you are experiencing, or try our short thyroid disorders symptom checker.

How hyperthyroidism is treated

According to the type of hyperthyroidism, your age and health status, and how serious the over-activity of your thyroid is, your doctor will choose a treatment option: that is best suited for you.

Anti-thyroid drugs prevent the thyroid gland from producing new thyroid hormones.1 Alternatively the thyroid tissue can be destroyed using radioactive iodine or by surgically removing parts of or the whole thyroid gland.1 The resulting hypothyroidism is then treated with appropriate medication.1,7

How thyroid hormones impact your heart

The heart is a major target of thyroid hormones. Any change in thyroid hormone levels will be responded to by the heart.

Too much thyroid hormone as a consequence of an overactive thyroid (hyperthyroidism) may cause:8

  • An increased and stronger heart rate, which can lead to palpitations and atrial fibrillation (irregular heart beat)
  • Higher blood pressure

Without treatment, an under- or overactive thyroid will worsen or accelerate any pre-existing heart disease or cause new conditions.

Mild hyperthyroidism affects the elderly heart

Mild hyperthyroidism is seen in 0.7–12.4% of the population.9 Patients with an overactive thyroid are assigned to two categories: patients with low, but detectable TSH values and patients with undetectable TSH values.10 Patients with undetectable TSH are at greater risk for developing heart problems such as atrial fibrillation, which is an arrhythmia with chaotic heartbeat that causes poor blood circulation. This is most frequently seen in the elderly with later diagnosis and pre-existing heart disease.9

US guidelines recommend that patients older than 60 years with undetectable TSH values should be treated.10 For younger patients without symptoms, close monitoring seems appropriate.10

  1. American Thyroid Association. Hyperthyroidism. 2014. Available at Last accessed February 2022.
  2. Hyperthyroidism symptoms. Available at Last accessed February 2022
  3. American Thyroid Association. Clinical thyroidology for the public: hyperthyroidism. Available at Last accessed February 2022
  4. British Thyroid Foundation. Thyroid disorders and osteoporosis. Available at Last accessed February 2022
  5. Everyday Health. Are you at risk for thyroid disease?. Available at Last accessed February 2022
  6. Hyperthyroidism. Available at Last accessed February 2022
  7. NHS Choices. Underactive thyroid (hypothyroidism) — treatment. Available at Last accessed February 2022
  8. Thyroid Foundation of Canada. The heart and the thyroid gland. Available at Last accessed February 2022
  9. Biondi B, Cooper DS. The clinical significance of subclinical thyroid dysfunction. Endocr Rev 2008; 29: 76–131.
  10. Bahn RS, Burch HB, Cooper DS et al. Hyperthyroidism and other causes of thyrotoxicosis: management guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists. Endocr Pract 2011; 17: 456–520


Date of preparation: February 2022