Thyroid function in patients with homozygous beta-thalassaemia.

Thyroid function was evaluated in 20 patients aged 8-30 years who were suffering from homozygous beta-thalassaemia. All patients have been receiving frequent blood transfusions and treated for the resulting transfusional iron overload with intramuscular injections of Desferrioxamine. Total thyroxine (T4), T3-uptake, total triiodothyronine (T3), and reverse triiodothyronine (rT3) were measured. In addition a standard TRH stimulation test was performed and blood samples were checked for the presence of thyroid antibodies. It was found that total T4 was significantly lower in the patients than in the controls. Total T3 and rT3 levels were similar in both patients and controls and all patients were negative for thyroid antibodies. T3 uptake in the patients was also statistically different from the controls resulting in significantly lower free thyroxine index (FT1). Basal TSH values were not different from the controls but the TSH increase following TRH stimulation was significantly higher in the patients suggesting, together with the low total T4 and FTI, a state of compensated hypothyroidism.