Overactive thyroid (hyperthyroidism): symptoms and when to test

An overactive thyroid, medically hyperthyroidism, means your thyroid makes too much hormone. Your body then runs at a higher pace: your heart rate speeds up, you lose weight without reason and you often feel restless. It is less common than an underactive thyroid, but the symptoms are usually more noticeable (De Leo 2016).

This article belongs to the overview about your thyroid and focuses on the overactive side.

What is an overactive thyroid?

With hyperthyroidism, production of T4 and T3 is too high. Your pituitary lowers TSH in response. So an overactive thyroid typically shows a low TSH with a raised free T4 and often free T3.

Which symptoms fit an overactive thyroid?

• Palpitations or a fast heartbeat
• Unintended weight loss despite normal appetite
• Restlessness, nervousness or irritability
• Excessive sweating and feeling hot
• Trembling hands
• Sleep problems

What are the causes?

A common cause is Graves' disease, an autoimmune process in which antibodies drive overproduction. Other causes include an overactive nodule and certain thyroid inflammations. How often each occurs varies worldwide, partly due to iodine intake (Taylor 2018).

Which blood values give insight?

Read more about your TSH level, about the opposite underactive thyroid, or about thyroid and weight.

When to have your thyroid tested?

There is no fixed rule, but many people choose to test when symptoms like palpitations and weight loss persist. You can have a thyroid function test at Vitalcheck without a referral. A low TSH always needs further investigation, so discuss an abnormal result with your GP.

References

• De Leo S, et al. Hyperthyroidism. Lancet. 2016. PMID: 27038492.
• Taylor PN, et al. Global epidemiology of hyperthyroidism and hypothyroidism. Nat Rev Endocrinol. 2018. PMID: 29569622.
• NHG-Standaard Schildklieraandoeningen. Dutch College of General Practitioners.

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.