Underactive thyroid gland (hypothyroidism)

In people with low thyroid function (known medically as hypothyroidism), the thyroid gland produces insufficient quantities of the thyroid hormones triiodothyronine (T3) and thyroxine (T4). This underproduction of thyroid hormones slows down metabolic processes in the body and causes a decline in the patient’s fitness.

On average, women are more likely to suffer from an underactive thyroid than men, with more diagnoses between the ages of 40 and 60 and the number of cases increasing the higher the age bracket.

Alongside goitres (also called strumas) and hyperthyroidism, hypothyroidism is one of the most common thyroid disorders.


Hypothyroidism manifests itself in the form of numerous symptoms, some of which can be very severe. These include, but are not limited to:

  • fatigue
  • poor concentration and fitness levels
  • increased sensitivity to cold
  • skin changes (cool, dry, rough, doughy, yellowish discolouration)
  • hair loss
  • muscle cramps
  • excessive weight gain without changing eating habits
  • a swollen face with thickened lips and an enlarged tongue
  • swelling around the eye sockets leading to a slit-like narrowing of the eyelids
  • depressed moods
  • constipation
  • a slow heartbeat, low blood pressure, an enlarged heart
  • circulatory disorders (tingling in various places)
  • low libido (lack of sexual desire)
  • For women: menstrual disorders
  • enlargement of the thyroid gland (struma/goitre)
  • changes in blood values

It should be noted that, especially in older people, often the only noticeable symptoms are sensitivity to cold, depression and/or low fitness levels, which often makes it difficult to diagnose an underactive thyroid, as the symptoms are initially attributed to ageing or other diseases such as the early stages of dementia.


An underactive thyroid may be caused by disorders in the functioning of the thyroid gland itself, problems with TSH production in the pituitary gland, or insufficient secretion of the hypothalamic hormone. For this reason, it is important to observe the distinction between different forms of hypothyroidism.

  • Primary hypothyroidism: the thyroid gland itself is the cause of the underactivity.
  • Congenital underactivity of the thyroid gland: the individual is born without a thyroid gland, the thyroid develops abnormally, or there are abnormalities in thyroid hormone production
  • Acquired thyroid dysfunction as a result of chronic thyroid inflammation (e.g. due to Hashimoto’s thyroiditis) or as a result of previous treatment for hyperthyroidism. Thyroid surgery or iodine deficiency may also result in hypothyroidism.
  • Secondary hypothyroidism: the pituitary gland does not produce enough TSH (hypopituitarism or pituitary insufficiency).
  • Tertiary hypothyroidism (very rare): the hypothalamus does not produce enough hormones.


If there is a suspicion of hypothyroidism, the doctor will begin by ascertaining the patient’s medical history (history) and asking questions about possible thyroid disorders in the family and the occurrence of any symptoms typical of this condition.

This is followed by a physical examination, during which the neck is palpated and the condition of the skin is checked. This is usually followed by a blood test with the aim of determining the TSH value, which is usually heightened if the thyroid gland is underactive. In addition, the T4 value in the blood is established. A low T4 value indicates manifest, i.e. a clearly recognisable, hypothyroidism.

In addition, the doctor may refer the patient for the following examinations:

  • ultrasound examination (sonography) to determine the size and condition of the thyroid gland
  • thyroid scintigraphy (used to examine the functioning of the thyroid gland in more detail)
  • fine-needle biopsy to take a tissue sample
  • antibody test to determine if Hashimoto’s thyroiditis is present


The hormone deficiency caused by an underactive thyroid can initially be regulated by taking hormone tablets containing the active ingredient L-thyroxine. However, the patient would need to take these for the rest of their life. L-thyroxine is a synthetic hormone that acts like the natural thyroid hormone T4 and is partly converted into the thyroid hormone T3 in the body.

Treatment with L-thyroxine is started at a low dose and then gradually increased until the optimal individual dose for each patient is reached.

Older people who have been diagnosed with low thyroid function need a lower amount of L-thyroxine because their hormone balance is different to that of younger people.


The amount of L-thyroxine a patient ultimately has to take per day depends on the basal TSH value and the subjective well-being of the patient. The doctor will monitor blood TSH at the earliest eight weeks after initiation of therapy or after each time the dose is adjusted. Once the correct dose has been reached, blood counts are usually checked once every six months and then once a year.


What characterises latent hypothyroidism?

In latent (i.e. hidden) hypothyroidism, the concentration of the thyroid hormones T3 and T4 is not (yet) reduced; it is only the TSH value (an important thyroid value that indicates the condition of the thyroid gland and whether it is producing enough hormones) is increased. For this reason, it is rare for symptoms like low fitness levels, poor concentration and fatigue to occur at this point, at least not to any noticeable extent.

How does hypothyroidism manifest itself in babies?

Babies born with congenital hypothyroidism display the typical symptoms of this disease immediately after birth. This means that they hardly move, do not drink and have weak muscle reflexes.


Because this can lead to delayed growth, slowed mental development and speech development disorders, it is important that the hormone deficiency is treated immediately.

How is hypothyroidism treated in pregnant women?

If a woman who already suffers from an underactive thyroid becomes pregnant, it is even more important for her to have regular check-ups for her hypothyroidism, because the body needs more thyroid hormones during pregnancy.

For this reason, expectant mothers with low thyroid function are given an increased dose of L-thyroxine, otherwise there is a risk of miscarriage or premature birth.

In addition, premature discontinuation of L-thyroxine tablets may lead to physical and mental harm to the unborn child, as the child’s thyroid gland does not begin to produce thyroxine (T4) itself until the twelfth week of pregnancy.

We find a specialist for you