Slow metabolism, a widely-discussed condition

This is a condition that produces a wide range of symptoms and which is blamed for a lot of things. It is a widely-discussed condition, and I hope to throw some light on it here.

Slow metabolism – Hypothyroidism
Slow metabolism, or hypothyroidism, means that there are abnormally low levels of thyroid hormones in the blood. These hormones control the metabolism, and low levels result in all the processes in the body being slowed more than normal.

If you have a slow metabolism, it is because you have abnormally low levels of thyroid hormones in your blood. It is a condition that develops gradually, and it causes worsening fatigue and exhaustion.

Other common symptoms are weight gain, slow digestion, increased need for sleep, sensitivity to cold, hair loss, dry skin and brittle nails.

Thyroid hormones are released by the thyroid gland, which is located in the throat, attached to the outside of the windpipe.

In order for the thyroid gland to produce hormones, it has to be stimulated by thyrotropin, a hormone that is produced and released by the pituitary gland. The mineral iodine is also required, as it is an important component of these hormones.

The thyroid hormones that play a role in metabolism are thyroxine and triiodothyronine. Low values of these are detected by the pituitary gland, which then tries to produce more thyrotropin in an attempt to get the thyroid gland to produce more thyroxine and triiodothyronine.

Children can be born with a slow metabolism, but it is most common in developing countries where there may be problems with dietary iodine levels. Low iodine levels in pregnant women may result in their children having poor thyroid development.

These children will then have problems with their growth and development. Slow metabolism is seen more frequently in women and it is more common with increasing age.

Symptoms of slow metabolism
Symptoms of slow metabolism often develop gradually. Increasing tiredness and a sensation of sluggishness are typical symptoms.

Other extremely common symptoms are weight-gain, slowed digestion, an increased need for sleep, sensitivity to the cold, hair loss, dry skin and brittle nails. Slow metabolism can produce symptoms in all the body’s organ system, and in women the clinical picture may include menstrual changes.

Depression, memory problems, dizziness, buzzing in the ears, hoarseness, a tingling sensation in the hands, and muscle and joint pain can also occur if slow metabolism is left untreated for a long time.

Half of all patients with long-term slow metabolism will have an enlarged thyroid gland, known as a goitre.

Treatment and prevention
Treatment consists of normalising the hormone levels in the blood, which is done by administering thyroxine in tablet form. Successful treatment results in normalisation of the thyrotropin level (in other words, it falls).

Regular blood tests are necessary at the start of treatment in order to find the correct dose.

Blood donor looking at camera

Investigation and diagnosis
A diagnosis is based on the symptoms, and it is confirmed by means of blood tests.

A suspicion of a slow metabolism can be based on typical symptoms. On examining a patient, the doctor will often find a slower-than-normal heart rate and delayed reflexes. In order to confirm the diagnosis, blood samples are taken in order to check levels of thyrotropin and thyroxine.

Slow metabolism is confirmed if thyrotropin is high and thyroxine is low. The blood is also checked for antibodies to the thyroid gland in order to find out if the slow metabolism is caused by the immune system.

Causes of slow metabolism
There are a lot of causes of slow metabolism, but the most common is the thyroid gland being damaged by the body’s own immune system, or by surgery to the neck area.

The most common cause of slow metabolism is damage to the hormone-producing thyroid gland, either by the body’s own immune system, or by surgery to the neck area.

A fault in the immune system may prevent the body from recognising the cells in the thyroid gland as its own, causing it to produce substances that attack and damage the thyroid gland. This is known as an autoimmune reaction.

This causes damage to the hormone-producing cells, resulting in reduced production of thyroid hormones. People with other autoimmune diseases, such as diabetes, coeliac disease (gluten intolerance) and articular rheumatism, are more likely to develop slow metabolism.

A family history of autoimmune disease is a significant risk factor. Some medicines such as amiodarone, lithium and interferon are known to damage the thyroid gland.

Surgery to the neck region may also produce a greater risk of developing slow metabolism if the thyroid gland is damaged. This is also the case with previous surgery or radiotherapy to an over-active thyroid gland or radiotherapy for cancer in the chest region.

A less common cause of slow metabolism is under-production of thyrotropin in the pituitary gland, which will often cause fairly mild symptoms.

It is also possible to have “temporary” slow metabolism. This can occur in women two to six months after giving birth, or it can accompany inflammation of the thyroid gland.

It usually goes away by itself, though some people may require short-term treatment with thyroid hormones.

Prognosis for slow metabolism
When treated, the prognosis for slow metabolism is good.

The prognosis is good when treated. In most people, slow metabolism will be a life-long condition, with the exception of temporary slow metabolism following childbirth or viral infection.

Facts about slow metabolism

  • Slow metabolism means that all the processes in the body work slowly.
  • Fatigue, tiredness, weight-gain, slow digestion, dry skin, hair-loss and brittle nails are all common symptoms.
  • Depression, dizziness, buzzing in the ears and poor memory are other common symptoms of slow metabolism.
  • If you have a slow metabolism, it is because you have abnormally low levels of thyroid hormones in your blood.
  • This is usually due to an autoimmune reaction, in which the body’s own defence system attacks the thyroid gland.
  • It may also be due to surgery or radiotherapy having damaged the thyroid gland.


Nurse using a tablet computer