Occult (Masked) Thyrotoxicosis with Supraventricular Arrhythmia and Hypertension

Abstract

The clinical diagnosis of hyperthyroidism is not always obvious in elderly patients in which supraventricular arrhythmia especially atrial fibrill ation may be dominant feature in the absence of goitre, classical eye signs and other signs of thyr oid hormone excess. DISCUSSION: The diagnosis of hyperthyroidism is difficult in elderly cases in absence of goitre, eye signs and other clinical manifestation of hormone excess. In the presented cases some signs of hormone excess were present. In some cases thyroid hormone within high normal range may be sufficient to trigger the onset of cardiac arrhythmia in susceptable persons. In such cases hyperthyroidi sm should not be excluded as a cause and so in unexplained or “lone” atrial fibrillation or tachy arrythmia without thyrotrophin releasing hormone test (in absence of hypopituitarism a blunt response of serum thyroid stimulating hormone after intravenous administration of 200 ug thyrotrophin releasing hormone). The fall was maximal after 9 weeks while serum thyroxin and thyrot rophin hormone levels did not change altho ugh 2 patients showed two fold increase in serum thyrotrophin levels after 9 weeks treatm ent with carbimazole. There was an increase of the antibodies level after discontinuation of carbimazole in three patients and the level remaine d unchanged in six and decreased in one.