The thyroid is often an underappreciated organ – the average person likely couldn’t locate it in the human body, let alone describe its function. However, it actually plays an important function in daily life, and you’ll soon notice if it stops working: you don’t know what you’ve got ‘til it’s gone.

The thyroid gland is found in the neck, just in front of the windpipe, in the shape of a butterfly.


The Location of the Thyroid Gland in the body
The thyroid gland in the neck.

The thyroid gland is stimulated by the hormone TSH (thyroid stimulating hormone), which is released by the pituitary gland in the brain. Upon receipt of this TSH hormone, the thyroid releases its own hormones, T3 and T4. These thyroid hormones flow in the bloodstream around the body, where they control the metabolism - the conversion of food into energy.

In short:

No thyroid hormones = no energy.


Thyroid malfunction

There are essentially two main types of thyroid disease: overactive and underactive thyroid.

Ideally, thyroid hormone levels should stay within a healthy range. When hormone levels fall outside these reference ranges, patients quickly begin to feel generally very unwell, with different symptoms for hypo and hyperthyroid diseases. 


1) Hypothyroidism

Underactive thyroid, otherwise known as hypothyroidism, is whereby the thyroid gland is not producing enough thyroid hormones. The causes for hypothyroidism are usually unknown, although sometimes a reduced thyroid function is due to an autoimmune reaction – called autoimmune thyroiditis. This means, that the body’s own immune system is mistakenly attacking the thyroid gland, destroying its cells, and thus reducing thyroid hormone output. As with all immune reactions (such as allergies and hay fever), this leads to inflammation – in this case, inflammation of the thyroid presents as a swelling of the neck known as 'Goitre'. Autoimmune thyroiditis is otherwise known as Hashimoto’s disease.

Symptoms of hypothyroidism include:

  • Fatigue
  • Exhaustion
  • Depression
  • Difficulty concentrating
  • Unexplained weight gain
  • Dry, itchy skin
  • Muscle cramps
  • Loss of libido
  • Unexplained cold sensation.

More women than men are affected by hypothyroidism, with approximately 1.5% and 0.1% affected respectively. Around 1 in 4,000 babies are born with congenital hypothyroidism, which is screened for in the UK when babies are five days old, using a blood spot test

For anyone experiencing symptoms of hypothyroidism, doctors would usually recommend a thyroid function test. This usually includes TSH, Free T4 (thyroxine), or T3.

A high TSH level, and low T4 level would indicate that the pituitary gland is releasing adequate TSH, but the thyroid is not responding: hypothyroidism.

At LDC, we offer this private blood test at all of our central London clinics. A standard thyroid blood test measures level free T4 and TSH levels, and costs just £86.40. Results are usually available same-day (if patients attend early enough in the day), and will be explained by phone or email by the GP.

Alternatively, a more thorough private thyroid test will cost £124.80, and this measures levels of free T3, free T4 and TSH. Again, results are usually available same day.

To thoroughly investigate the cause of thyroid disease, a doctor may also recommend a thyroid blood test for thyroid antibodies. This thyroid panel costs £211.20, and is the most thorough, measuring:

  • Free T3
  • T4
  • Free T4
  • TSH
  • Thyroid antibodies

When investigating the cause of malaise, doctors may also recommend a more general health screen, to rule out other causes of such symptoms. This may include a full blood count, and tests for liver function, diabetes, anaemia, vitamins B, C, D, and adrenal function. Tiredness, for example, can be caused by a variety of conditions, such as anaemia, insomnia or pregnancy.


If you’ve been diagnosed with hypothyroidism, the treatment is fairly straightforward: taking daily hormone replacement therapy, to replace the thyroid hormones not being naturally produced. This medication is called Levothyroxine, and the dose prescribed for you will depend on how underactive your thyroid is.

Unfortunately, hypothyroidism is a lifelong disease, and there is currently no cure or treatment to bring back lost thyroid function, so hypothyroid patients must take Levothyroxine for the rest of their lives.

Complications can arise if underactive thyroid is left untreated, such as:

  • Heart disease
  • Goitre
  • Problems during pregnancy
  • Myxoedema coma (a rare, but serious condition)


2) Hyperthyroidism

Overactive thyroid disease is where excess levels of thyroid hormones are produced by the thyroid gland. Again, the causes of hyperthyroidism are usually unknown. Like with hypothyroidism, there is also an autoimmune condition that leads to hyperthyroidism – called Graves’ disease. Again, this is where the body’s immune system mistakenly attacks the thyroid, this time leading to increased thyroid hormone output. This leads to high levels of thyroid hormones, T3 and T4, causing the following symptoms:

  • Hyperactivity, excess energy
  • Nervousness
  • Anxiety
  • Unexplained weight loss
  • Goitre

There are a variety of potential treatments for an overactive thyroid, including medication, radioiodine treatment, or even surgery. These reduce thyroid hormone output, shrink the thyroid, or remove part of the thyroid gland, respectively. 

Treatments depend on severity of hypothyroidism, and can be discussed with your GP during a consultation. 

Severe cases of under or overactive thyroid diseases may require a referral to a specialist - an Endocrinologist.


Long-term thyroid monitoring

If you’ve been diagnosed with thyroid disease, you need to ensure your thyroid hormone levels stay within normal healthy range. This can be accurately done by regular thyroid health blood testing, and will help identify if treatment is working efficiently, or medications need to be altered.

Although it must be noted, that healthy ranges may vary between individuals, depending on factors such as age and gender.

Thyroid danger levels table

Table to show average healthy ranges for thyroid hormone T4 and TSH.



It produces thyroid hormones, which play a main role in the body’s metabolism – the process of chemical reactions, such as those to releasing energy. These thyroid hormones include triiodothyronine (T3) and thyroxine (T4), which travel around the blood stream to every part of the body.