Overactive Thyroid Symptoms: Early Signs, Causes, and Treatment Options

If you’re experiencing unexplained changes such as weight loss, rapid heartbeat, or constant feelings of anxiety and tiredness, you might be wondering if these are symptoms of an overactive thyroid. Also known as hyperthyroidism, this condition happens when your thyroid gland—located at the front of your neck—produces too much thyroid hormone.

These hormones regulate metabolism, energy, mood, heart rate, and more. When levels are too high, your body can feel as though it’s running on overdrive. Understanding the symptoms and knowing when to speak with a GP can make all the difference.

What Causes an Overactive Thyroid?

There are a few different reasons why the thyroid may become overactive. Graves’ disease is the leading cause of an overactive thyroid. It occurs when the immune system mistakenly attacks the thyroid and makes it release too much hormone.

Other causes include:

Thyroid nodules (small lumps that become overactive)
Thyroiditis (inflammation that can trigger a hormone surge and impact your autoimmune system)
Excess iodine (from medication or diet)
Certain medications (such as some heart medicines, e.g. amiodarone)

It is important to identify the cause to ensure correct treatment.

What Are the First Signs of an Overactive Thyroid?

Hyperthyroidism often begins with subtle changes that are easy to dismiss. Many people first notice:

Unintentional weight loss that happens quickly
A heartbeat that feels faster than usual or irregular
Persistent feelings of anxiety, restlessness, or nervous energy
Shaky hands or slight tremors
Trouble sleeping or feeling unusually alert at night
Feeling warmer than usual or experiencing excessive sweating

These early signs can easily be mistaken for stress or everyday lifestyle factors, so it’s important to notice if they continue over time.

Common Overactive Thyroid Symptoms

As hyperthyroidism progresses, more symptoms can start to show. People may notice persistent tiredness, weakened muscles, a swollen neck (goitre), changes in the eyes such as redness, dryness, or bulging, and hair that becomes thin or nails that grow brittle.

Women may also notice lighter or less frequent periods, while both men and women can experience reduced sex drive. More frequent bowel movements or diarrhoea are also common.

Symptoms can vary from person to person, but if you notice several of these signs at the same time, it’s a good idea to speak with a GP.

Why Early Detection Matters

When left untreated, an overactive thyroid can put strain on the body. Potential complications include heart rhythm problems such as atrial fibrillation, fragile bones due to osteoporosis, or eye problems linked with Graves’ disease. In rare cases, dangerously high hormone levels can lead to a medical emergency called thyroid storm.

Hyperthyroidism can also affect pregnancy, increasing the risk of preterm birth or other complications. This is why early diagnosis and management are so important.

How Do You Treat an Overactive Thyroid?

The good news is that an overactive thyroid can usually be treated successfully. Your GP will suggest the most suitable approach depending on the cause, your age, and your overall health.

Treatment options may include:

Anti-thyroid medications to help slow down hormone production
Beta-blockers to relieve symptoms such as rapid heartbeat, tremors, or excessive sweating
Radioactive iodine therapy, which gradually reduces thyroid activity
Surgery (thyroidectomy) to remove part or all of the thyroid gland, typically recommended when other treatments aren’t suitable

In some cases, treatment can cause the thyroid to slow down too much, leading to hypothyroidism (an underactive thyroid). If this happens, lifelong thyroid hormone replacement may be needed. Regular follow-ups and blood tests are an essential part of ongoing care.

Diagnosing Hyperthyroidism

If you think you might have an overactive thyroid, a GP can guide you through the diagnosis. This usually involves:

Discussing your symptoms and medical history with your doctor
Performing a physical examination, including checking your pulse, looking for tremors, and examining the neck for swelling
Blood tests to measure thyroid hormones (T3 and T4) and TSH levels
Additional tests, such as an ultrasound or antibody tests, if necessary

Recognising the Pattern of Symptoms

It may help to think of overactive thyroid symptoms in groups:

Energy & Mood: anxiety, irritability, poor sleep, fatigue
Weight & Metabolism: unexplained weight loss, heat intolerance, sweating
Heart & Circulation: rapid heartbeat, irregular pulse, palpitations
Appearance: thinning hair, brittle nails, warm and moist skin
Digestive System: frequent bowel movements or diarrhoea
Neck & Eyes: swelling in the neck (goitre), red or bulging eyes
Reproductive Health: lighter or missed periods, reduced libido

Spotting a combination of these symptoms is a strong reason to seek medical advice.

Conclusion

Your thyroid may be small, but when it produces too much hormone, the effects can ripple across your entire body. From early warning signs like weight loss and palpitations to more advanced issues such as fatigue, sleep problems, and mood changes, overactive thyroid symptoms can be disruptive—but they are very treatable with the proper care.

If you’re worried that you might have symptoms of hyperthyroidism, don’t wait. Book a consultation with GP24 today and get peace of mind with a doctor available 24/7, wherever you are in Ireland.