Endocrine Abstracts

Aim: To assess cumulative incidence and risk factors for amiodarone-induced thyroid dysfunction (AITD) in a large cohort of Romanian subjects.

Subjects and methods: One hundred and forty-four patients (59 M/85 F), mean age 61.4±0.9 years, treated 2.4±0.2 years with amiodarone were assessed for TSH, TT₃, TT₄ (immunoradiometric assays) and FT₄, TPO Ab (microenzymatic immunoassays). Thirty-three patients were residents in areas with mild/moderate iodine deficiency and 111 patients from areas with normal iodine intake. Kaplan Meier curves were used for estimation of cumulative incidence and timing of AITD.

Results: AITD occurred in 89/144 patients (61.8%): 60 patients (41.7%) developed thyrotoxicosis (AIT), 29 patients (38.1%) hypothyroidism. Type 1 and mixed forms of AIT prevailed (43 patients, 71.6%). Estimated mean time for AITD was 3.8±0.33 years; estimated cumulative incidence was 25% at 1 year, 50% at 2 years and 75% at 5 years of treatment. Patients from iodine-deficient areas developed thyroid dysfunction significantly more frequent (25% at 0.5 years, 50% at 2 years and 75% at 4 years) and earlier (2.2±0.3 years) as compared to those from iodine sufficient areas (25% at 1.5 years, 50% at 3 years and 75% at 7 years), mean time 4.2±0.4 years, P=0.001, log rank Mantel-Cox. Patients with TPO Ab ≥ 100 IU/ml developed thyroid dysfunction significantly more frequent (25% at 0.75 years, 50% at 1 year and 75% at 2.5 years) and earlier (2.2±0.7 years) as compared to those with TPO Ab < 100 IU/ml (25% at 1.1 years, 50% at 3 years and 75% at 5 years), mean time 3.9±0.5 years, P=0.046. No differences regarding age, gender, cumulative amiodarone dose were noticed.

Conclusion: Iodine deficiency and thyroid autoimmunity are the main risk factors for amiodarone-induced thyroid dysfunction in Romania.