Underactive thyroid (hypothyroidism)

In the case of hypothyroidism, there is a deficiency of the thyroid hormones triiodothyronine and thyroxine in the body.

In most cases, there is acquired primary hypothyroidism, where thyroid function is normal at the time of birth and the symptoms only develop during the course of life. Primary means that hormone production is disturbed directly in the thyroid gland. Possible causes for this are

Hashimoto's thyroiditis

The most common cause of hypothyroidism is Hashimoto 's thyroiditis. As part of this autoimmune disease, autoantibodies are formed against components of the thyroid cells for reasons that are still unknown. The chronic inflammation triggered leads to damage to the thyroid gland with a decrease in hormone production.

Medically triggered (iatrogenic)

In some cases, hypothyroidism is caused by medical intervention. This may be intentional or unintentional. Examples of this are operations in which the thyroid gland has been completely or partially removed. Hypothyroidism can also be caused by taking thyroid-inhibiting medication (thyreostatics) or as a side effect of other medication (e.g. amiodarone).

Lack of trace elements

A pronounced deficiency of iodine or selenium can lead to hypothyroidism.

Secondary or tertiary hypothyroidism

In rare cases, hypothyroidism is the result of a problem in the upstream hormonal regulatory circuits in the pituitary gland (hypophysis) or in the brain (hypothalamus). This is referred to as secondary or tertiary hypothyroidism.

Congenital hypothyroidism

A congenital form is also rare, in which, for example, a missing or only partially developed thyroid gland or receptor defects are responsible for hypothyroidism.

A lack of thyroid hormones affects most organs in the human body. Patients with hypothyroidism usually feel weak and tired. The thyroid gland tries to compensate for the reduced hormone production with increased growth, which is why people with hypothyroidism are often diagnosed with an enlarged thyroid gland (goiter).

The following symptoms are indicative of hypothyroidism:

• Tiredness (fatigue) and weakness
• listlessness
• exhaustion
• Reduced physical and cognitive performance
• Depressive moods, sadness
• Weight gain (sometimes despite changes in eating habits)
• Excessive sensitivity to cold
• Cycle irregularities and possibly reduced fertility as a result
• Constipation (constipation)
• Cool, dry and/or pasty skin
• Disorders of nail growth
• Hair loss (effluvium)

Particularly in older patients, the symptoms are often unspecific and the diagnosis of hypothyroidism is difficult.

Newborns with hypothyroidism are often conspicuous by reduced drinking behavior, digestive disorders and reduced motor activity. Hypothyroidism has a negative effect on the development and growth of children, which is why children with hypothyroidism can show delayed mental and physical development.

In order to diagnose a thyroid disease or dysfunction, the thyroid function (hyperthyroidism, hypothyroidism or normal function) is determined via a blood test and the thyroid structure (morphology) is examined using ultrasound after a detailed discussion including a medical history (anamnesis). These two parameters do not necessarily correlate and must always be considered in combination in order to ultimately arrive at a diagnosis and subsequently adequate treatment.

Examination of thyroid function

The healthy function of the thyroid gland is based on the following mechanism: the thyroid gland secretes the free thyroid hormones thyroxine (fT4) and a small amount of triiodothyronine (fT3), which are essential for the metabolism, whereby fT3 is also converted from fT4 outside the thyroid gland in various organs and made available to the body.

In the rare cases where there is a specific cause of hypothyroidism, this should be treated, for example by discontinuing causative medication (thyrostatic drugs, amiodarone) or compensating for an iodine deficiency.

Hypothyroidism can normally be treated very well with hormone replacement therapy. The aim of treatment is to compensate for the hypothyroidism using thyroid hormone in the form of tablets so that the resulting symptoms subside. The thyroid hormone, which the thyroid gland can no longer produce on its own, is therefore permanently replaced by a hormone tablet (hormone replacement). Patients with hypothyroidism usually have to take thyroid hormone tablets every day for the rest of their lives. Regular checks and, if necessary, adjustments to the dose of medication - especially in special phases of life such as the desire to have children, pregnancy and breastfeeding - are extremely important.

Treatment is started with a low dosage and slowly increased until the desired effective dose is achieved.

Timely treatment with thyroid hormones is also important for newborns and children with congenital hypothyroidism in order to prevent possible developmental disorders and enable healthy development.

In most cases, hypothyroidism has a good prognosis as it can be adequately treated with hormone preparations. Existing symptoms such as tiredness and reduced performance usually disappear with substitution.

Newborns with hypothyroidism have a good chance of normal development if the disease is recognized and treated early. However, if hypothyroidism is detected too late, growth and developmental disorders can no longer be reversed.

In most cases, hypothyroidism is caused by Hashimoto's thyroiditis, against whose autoimmune reaction there are no preventive measures.

Hypothyroidism caused by iodine deficiency can be prevented by sufficient iodine intake. In German-speaking countries, iodine is added to conventional table salt to ensure an adequate supply.

If there are indications of hypothyroidism, a doctor should be consulted and checked.