Your thyroid is a gland (an organ that releases hormones). It’s located in your neck and produces two hormones:

• Thyroxine (T4)
• Triiodothyronine (T3)

These hormones are responsible for normal cell function and metabolism.

Metabolism is the rate that your cells convert food and drink into energy. Your body burns energy all the time, even when you are resting. This is known as your basal metabolic rate (BMR).²

If your thyroid produces too many hormones, it increases your metabolism. And if it produces too little, your metabolism will slow down.

Thyroid disease refers to any condition that affects your thyroid function.¹

There are many different types of thyroid disease but the two most common are an overactive thyroid (hyperthyroidism) or underactive thyroid (hypothyroidism).³

Hypothyroidism is a term used to describe an underactive thyroid. Symptoms include:

There are many reasons why you might have an underactive thyroid. These include:

• Hashimoto’s disease
• Previous thyroid treatment
• Not getting enough of the nutrient, iodine, in your diet
• Being born with an underdeveloped thyroid
• Health issues affecting your pituitary gland.⁵

Hashimoto’s disease is a type of autoimmune condition that can cause an underactive thyroid. It runs in families and often impacts women more than men. If you have the condition, you may find you have visible swelling, pain or discomfort in your neck as well as the symptoms of hypothyroidism.^6,7

Hyperthyroidism is a condition that causes your thyroid gland to produce too much thyroxine and triiodothyronine. These hormones are responsible for:

• Controlling the amount of protein in your body
• Controlling how your body burns fat and carbohydrates
• Regulating your core body temperature.¹⁰

The symptoms of hyperthyroidism can include:

• A rapid heartbeat
• Sweating
• Swelling in the neck
• Thinning hair
• More frequent bowel movements
• Heat sensitivity
• Increased appetite
• Tremors in your hands and fingers
• Weight loss.¹⁰

Hyperthyroidism causes weight loss because it speeds up your metabolism, meaning you burn more energy at rest. If you are receiving treatment for your hyperthyroidism, you may find that you gain weight. This is because your medicine is helping your thyroid to function properly. You can manage weight gain through exercise and eating a healthy, balanced diet.

If you have lost weight or have any other symptoms of an overactive thyroid, speak to your GP. They will arrange a thyroid function test for you. It is a type of blood test that analyses the amount of thyroid stimulating hormone, thyroxine and triiodothyronine in your blood. Your results will give your GP an indication of how your thyroid is functioning.¹¹

If they suspect that you have an overactive thyroid, you may be referred for further blood tests to find possible reasons for your hyperthyroidism. You may also have a scan of your thyroid to check for any lumps.¹¹

Treatment for an overactive thyroid will depend on how severe your symptoms are. Your GP or specialist doctor will discuss your options with you, but it may include taking tablets, having radioactive iodine treatment or surgery. Treatment is carried out to get your thyroid levels under control. It may also be used to reduce swelling, size and shape of your thyroid gland.¹²

If you have a thyroid condition your GP will advise you on the ways you can manage your weight. If you’ve been prescribed medication, it may help you to reach a healthy BMI.

But regular exercise and a healthy diet can also help you manage your weight.

If you have hypothyroidism, you might also be able to use a GLP-1 weight loss medication like Wegovy or Mounjaro. You should speak to your prescriber (either your pharmacist or GP) about your medical history, any medications you use and your weight loss goals. They will be able to assess whether you’re eligible and if your current medication use is compatible with GLP-1 medicines.