As the symptoms of hypothyroidism are very unspecific, the disease may remain undetected for a long time. The diagnosis is made on the basis of a laboratory blood test.
Manifest hypothyroidism is characterized by the deficiency of triiodothyronine and thyroxine (usually abbreviated as T3 and T4) described above.
There is also so-called latent or subclinical hypothyroidism. In this case, the body is still able to regulate the levels of T3 and T4 up to the normal range through increased stimulation of the thyroid gland. Latent hypothyroidism is usually asymptomatic, but can develop into manifest hypothyroidism.
It is estimated that around five percent of the population in Germany is affected. Women are affected about five times more frequently than men.
The thyroid gland and the molecular representation of the T3 and T4 hormones © Kateryna_Kon | AdobeStock
Hypothyroidism can be congenital or acquired.
Congenital hypothyroidism requires urgent treatment as early as infancy. Otherwise there is a risk of considerable physical and mental developmental disorders.
Acquired primary hypothyroidism is the most common form of hypothyroidism. In this case, the cause of the hormone deficiency lies directly in the thyroid gland.
In contrast, the very rare secondary hypothyroidism is triggered by pathological processes in the pituitary gland. These disorders reduce the production of the control hormone TSH. The thyroid gland itself is not impaired, but is not sufficiently stimulated by TSH.
Possible causes of primary hypothyroidism are
- autoimmune inflammatory processes that destroy thyroid tissue (e.g. Hashimoto's thyroiditis)
- Loss of thyroid tissue due to thyroid surgery, radioiodine therapy for thyroid diseases or radiation to the head and neck area
- Pronounced iodine deficiency
- Severe iodine excess
- Possible selenium deficiency
Taking certain medications can also promote the development of primary hypothyroidism. These include
A large number of the following symptoms usually occur in connection with hypothyroidism:
- constant tiredness
- listlessness
- depression
- Concentration and memory disorders
- constant freezing
- body temperature too low
- slowed heartbeat
- edema (swelling of the face and limbs due to water retention in the tissue)
- joint pain
- muscle weakness
- Loss of appetite, constipation, nausea
- noticeable weight gain
- dry, itchy skin
- so-called myxedema - a doughy thickening of the skin
- brittle nails, hair loss
- Cycle disorders in women, libido disorders, reduced fertility
The combination of symptoms from several symptom groups indicates hypothyroidism. However, false positive or negative (self-)diagnoses are easily possible. A blood test provides clarity.
Hypothyroidism may or may not be accompanied by conspicuous changes in the thyroid gland:
- Enlarged thyroid gland(goiter) - especially in the case of iodine deficiency and congenital hypothyroidism
- Reduced thyroid gland - when the thyroid gland is destroyed, for example by autoimmune inflammatory processes
Constant fatigue is one of the symptoms that can occur with hypothyroidism © pix4U | AdobeStock
Hypothyroidism is diagnosed on the basis of a laboratory blood test. The level of thyroid-stimulating hormone (TSH) and the thyroxine (T4) level are measured. It is also possible to determine the triiodothyronine (T3) level, but this is not usually done as it does not provide any additional information.
An elevated TSH level is decisive for the diagnosis, particularly in the case of frequent primary hypothyroidism. The elevated TSH level is the body's first reaction to low T3 and T4 production.
In the case of latent hypothyroidism, the TSH increase can still bring the T3 and T4 levels up into the normal range. Increased TSH values and T3 and T4 values in the (lower) normal range are then measured.
Subnormal T4 levels are characteristic of manifest hypothyroidism in addition to elevated TSH levels. Free T4, abbreviated as fT4, is usually measured.
The most common cause of hypothyroidism is Hashimoto's thyroiditis. To detect it, thyroid antibodies are usually also determined (MAK and TAK). Unlike Graves' disease ("TRAK" antibodies), "MAK" and "TAK" do not have a stimulating effect. Instead, they gradually destroy the thyroid tissue, resulting in hypothyroidism.
As a rule, an ultrasound examination of the thyroid gland is also carried out in cases of hypothyroidism.
Regardless of its cause, manifest hypothyroidism is treated with thyroid hormones. The active substances available are levothyroxine (L-thyroxine) and liothyronine, which is structurally identical to natural triiodothyronine (T3).
L-thyroxine is usually used for therapy. In order to find the right individual dose and keep side effects to a minimum, the medication is "snuck in": Initially, a low dose is prescribed. After four weeks at the earliest, the TSH value is checked and the dose increased if necessary.
This procedure is repeated until the symptoms have improved significantly and the TSH level is within the normal range.
Combination preparations for hypothyroidism contain combinations of levothyroxine and liothyronine (T3 and T4). They are not prescribed as the drug of first choice for primary acquired hypothyroidism. However, combinations of T3 and T4 can help some patients in whom L-thyroxine alone does not have a sufficient effect.
Latent hypothyroidism can also be treated with L-thyroxine if symptoms are present.
Treatment of congenital or acquired hypothyroidism with thyroid hormones must usually be continued for life. Hypothyroidism cannot be cured.
However, if medication is taken correctly and regularly, the prognosis is favorable: most sufferers can continue to live their lives without significant restrictions to their health and quality of life. However, the medication must not be discontinued abruptly and independently.
In order to avoidserious hormonal imbalances, the dose should not be changed abruptly, but only gradually. After starting the medication or changing the L-thyroxine dose, the TSH value needs at least four weeks. Only then will it reach its new equilibrium. After this period, it is checked whether the value is now within the normal range or whether the dose needs to be adjusted.
If the TSH value is normal and there are no symptoms, follow-up checks are initially carried out every six months and then annually.
