High prevalence of thyroid dysfunction in adult patients with beta-thalassemia major submitted to amiodarone treatment.

Amiodarone may induce hyper- or hypothyroidism. Patients with beta-Thalassemia Major (beta-Thal) have an increased prevalence of primary hypothyroidism and often require amiodarone for hemosyderotic cardiomyopathy. Aim of this study was to retrospectively evaluate thyroid function in beta-Thal adult patients on long-term amiodarone. The study group consisted of twenty-two (21 males, 1 female; age: 23-36 yr) beta-Thal patients submitted to long-term (3-48 months) amiodarone therapy from January 1991 to July 1996. Controls included 73 beta-Thal patients (23 males and 50 females aged 25-35 yr) not treated with amiodarone. In all cases serum free thyroid hormones, thyrotropin and thyroid autoantibodies were evaluated. A higher prevalence of overt hypothyroidism (5/22 [22.7%]) as compared to controls (3/73 [4.1%], p=0.02) was found in beta-Thal patients < or = 3 months after starting amiodarone, while the prevalence of subclinical hypothyroidism was similar in amiodarone-treated (18.2%) and untreated (15%) beta-Thal patients. Overt hypothyroidism resolved spontaneously after amiodarone withdrawal in 1 case, while the remaining patients were maintained euthyroid on amiodarone by L-thyroxine administration. After 21-47 months of amiodarone therapy, 3 patients (13.6%) developed thyrotoxicosis (2 overt and 1 subclinical), which remitted shortly after amiodarone withdrawal. No case of hyperthyroidism was observed in beta-Thal controls (p=0.012 vs amiodarone-treated patients). In conclusion, amiodarone administration is often associated in adult beta-Thal patients to a rapid progression of the pre-existing subclinical hypothyroidism, but transient thyrotoxicosis may also be observed after a longer period of therapy. These findings should be carefully considered in the management of these patients.

Circulating soluble IL-2 receptor levels are low in patients with hypothyroid autoimmune thyroiditis.

In hypothyroid patients serum soluble IL-2 receptor levels showed scattered and conflicting results. In our report we studied circulating soluble interleukin 2 receptors in 22 patients with hypothyroid autoimmune thyroiditis before L-thyroxine treatment and when the patients became euthyroid. The mean of soluble Interleukin 2 receptor levels in the hypothyroid state was 48.6 pmol/l (95% confidence interval, 45.6-51.5) statistically lower than in the controls (95% confidence interval, 86.4 pmol/l, 83.3-89.4) (p < 0.0001). When the patients became euthyroid during L-thyroxine treatment, soluble Interleukin 2 receptor levels increased, showing mean values comparable to the controls. A positive high correlation (p < 0.001) was observed between soluble Interleukin 2 receptor levels and thyroxine free levels in the hypothyroid as well as in the euthyroid state and between soluble Interleukin 2 receptors and the mean weekly L-thyroxine dose. Our study confirmed that in the hypothyroid state, the behaviour of soluble Interleukin 2 receptors is anomalous as compared to other autoimmune diseases. In fact a strict relationship exists between the levels of thyroid hormones and soluble Interleukin 2 receptors but not between the latter and antithyroid antibodies. These results agree with those supporting a role for thyroid hormones in the regulation of the immune system. They also suggest that the measurement of soluble Interleukin 2 receptors could be used as a marker of the peripheral action of thyroid hormones.