Endocrine Abstracts

Background: Prevalence and type of amiodarone-induced thyroid dysfunction in a population depend on geographical iodine intake.

Aims: To assess differences in amiodarone-induced thyrotoxicosis pattern before and after iodine supplementation.

Patients and methods: 84 patients (41M/43F) with amiodarone-induced thyrotoxicosis, aged 60.1±11.9 years, were retrospectively reviewed. 28 patients were resident in former iodine-deficient areas. TSH, FT₄ and total T₃ were measured by chemiluminescence; 2 h and 24 h radioiodine (¹³¹I) uptake and color flow Doppler were performed.

Results: Type 1 amiodarone-induced thyrotoxicosis (AIT) was diagnosed in 21 cases (25%), type 2 in 26 cases (30.9%) and mixed type in 37 cases (44%). Before universal salt iodization were diagnosed 38 cases (type 1 AIT in 12 cases – 31.6%, type 2 in 14 cases – 36.8% and mixed type in 12 cases – 31.6%); after universal salt iodization were diagnosed 46 cases (type 1 AIT in 9 cases – 19.6%, type 2 in 12 cases – 26% and mixed type in 25 cases – 54.3%); Patients with type 1 AIT were significantly younger (62.5±9.6 years vs 56.1±12.8 years, P=0.05), with significantly higher radioiodine uptake at 24 h (median 7% vs median 1%, P=0.022) and had higher thyroid volume (29.9±14.8 ml vs 19.9±8.6 ml, P=0.015) than patients with type 2 AIT. Patients with type 1 AIT had higher total T₃ levels than patients with type 2 AIT (340.9±157.4 vs 246.7±135.9 ng/dl, P=0.06) and type 3 AIT (216.4±111.8 ng/dl, P=0.003, respectively). There were no statistically significant differences in body mass index, amiodarone treatment duration, amiodarone cumulative dose, FT₄ levels between AIT type 1, 2 and mixed type.

Conclusion: After universal salt iodization, AIT type 2 and mixed type prevailed in our geographical area.