Die Autoimmunthyreoiditis (AIT) ist eine organspezifische Autoimmunerkrankung, die
durch eine genetische Prädisposition, epigenetische Mechanismen und auch Umweltfaktoren
entstehen kann. Der Beitrag diskutiert die aktuelle wissenschaftliche Literatur zur
AIT sowie die Empfehlungen zur Levothyroxin (LT4)-Substitution vor dem Hintergrund der aktuellen Leitlinien der American Thyroid Association
(ATA) und European Thyroid Association (ETA).
Abstract
Autoimmune thyroiditis (AIT) is not only one of the most prevalent human autoimmune
diseases, but also the most frequent cause of primary hypothyroidism. It is characterized
by lymphocytic infiltration of the thyroid gland with subsequent gradual destruction
and fibrous replacement of thyroid tissue. Genetic predisposition, epigenetic modifications
and environmental factors are suspected as disease triggers. Signs and symptoms of
hypothyroidism include fatigue, bradycardia, constipation and cold intolerance. In
subclinical hypothyroidism, symptoms may be absent. The diagnosis of AIT is based
on the presence of antibodies against thyroid specific antigens, primarily anti-thyroid
peroxidase antibodies and on a sonographically proven reduced echogenicity of the
thyroid parenchyma. The diagnosis of concomitant hypothyroidism is primarily based
on clinical signs and symptoms as well as measurement of thyroid-stimulating hormone
(TSH)-concentration. Subclinical hypothyroidism is characterized by elevated TSH with
normal serum free thyroxine (fT4) and triiodothyronine (fT3) levels, while in manifest hypothyroidism serum fT4 and fT3 levels are reduced. Levothyroxine (LT4) treatment in subclinical hypothyroidism is a controversy in the scientific literature
and should be discussed individually. It not only depends on the level of TSH-elevation,
but also on other factors, such as patient age, presence of comorbidities and clinical
symptoms of hypothyroidism. In contrast, overt hypothyroidism and subclinical hypothyroidism
with a TSH-level > 10 mIU/L is a strong indication for LT4 administration, aiming at rapid achievement of euthyroidism. In patients with dissatisfaction
due to persistence of symptoms despite optimal LT4-treatment LT4/T3-combination therapy should be considered, based on expert opinion.
Schlüsselwörter
Autoimmunthyreoiditis - subklinische Hypothyreose - Thyroxin - LT4/T3-Kombinationstherapie
Key words
autoimmune thyroid disorder - subclinical hypothyroidism - thyroxine - LT4/T3-combination
therapy
