Medical Encyclopaedia › Hypothyroidism (short definition)
In brief: In hypothyroidism, the thyroid gland produces too little of the hormones thyroxine (T4) and triiodothyronine (T3). As these hormones drive the metabolism of many organs, numerous bodily functions slow down.
Causes
The most common cause in Germany is the autoimmune disease Hashimoto’s thyroiditis. Other causes are thyroid surgery or radioiodine therapy, severe iodine deficiency, certain medicines such as amiodarone or lithium, and congenital disorders, which are detected through newborn screening.
Symptoms
Typical symptoms are tiredness, lack of drive, sensitivity to cold, weight gain, constipation, dry skin, hair loss, difficulty concentrating and low mood. The symptoms often develop gradually and are non-specific.
Diagnosis
The most important screening test is the TSH value: it is raised when the thyroid is underactive. In addition, free thyroxine (fT4) and antibodies such as TPO antibodies are measured; an ultrasound scan shows the structure of the thyroid. A slightly raised TSH with normal fT4 is called subclinical hypothyroidism, which does not always need to be treated.
Treatment
The missing hormones are replaced with levothyroxine, which is taken in the morning on an empty stomach about 30 minutes before breakfast. The dose is adjusted step by step based on the TSH value; treatment is usually lifelong. Coffee, calcium and iron preparations and some medicines can interfere with absorption. Close monitoring is particularly important during pregnancy.
Related terms in the encyclopaedia
Thyroid gland, TSH, Free thyroxine, Hashimoto’s thyroiditis, TPO antibodies, Levothyroxine, Iodine deficiency, Hyperthyroidism
Sources
- Deutsche Gesellschaft für Allgemeinmedizin und Familienmedizin (DEGAM): S2k-Leitlinie Erhöhter TSH-Wert in der Hausarztpraxis
- IQWiG: gesundheitsinformation.de – Gesundheitsinformationen des Instituts für Qualität und Wirtschaftlichkeit im Gesundheitswesen
Note: This article is for general information and does not replace advice, diagnosis or treatment from a doctor or pharmacist. Last updated: October 2026.