Endocrine Abstracts

Introduction: Subclinical hyperthyroidism is a syndrome with vague clinical symptoms. It may cause tachycardia, loss of weight or no symptoms at all. Subclinical hyperthyroidism may occur in middle age and in the elderly. It may be related to the occurrence of atrial fibrillation. Subclinical hyperthyroidism may be the result of an autonomous goiter, may occur in the course of follow-up of hypothyroidism, as the needs for treatment may vary over time and substantially diminish in middle and old age and may occur in the context of autoimmune thyroiditis.

Aim: The aim was to present a cohort of patients presenting with atrial fibrillation who were subsequently diagnosed with subclinical hyperthyroidism.

Methods: A cohort of 31 patients, 20 male and 11 female, aged 48–72 years presented with atrial fibrillation. Levels of blood TSH, freeT₄, freeT₃, anti-TPO ab and anti-Tg ab were measured and a thyroid ultrasonogram was performed.

Results: TSH levels were found to be diminished. FreeT₄ and freeT₃ levels were found to be normal. Anti-TPO and anti-Tg ab were positive in 18 and 15 patients, respectively. In 20 of the group hypothyroidism was diagnosed as the underlying thyroid illness. Treatment was adjusted to the needs of the patients. In 7 of the patients a multinodular goiter was diagnosed. Antithyroid agents were administered in this group. In 4 patients within the cohort autoimmune thyroiditis was diagnosed. After treatment adjustment in the hypothyroid group episodes of atrial fibrillation decreased in frequency and in two of the patients they were almost eliminated. After antithyroid drug administration in the goiter group episodes of atrial fibrillation were attenuated.

Conclusions: Atrial fibrillation may be the presenting symptom of subclinical hyperthyroidism. Subsequent diagnosis and proper management of subclinical hyperthyroidism may aid in the management of atrial fibrillation. We propose that patients with atrial fibrillation should be screened and appropriately treated for an underlying thyroid disorder.