Primary hypothyroidism and the low T3 syndrome in thalassaemia major

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Abstract
Basal thyroid function was assessed from the serum thyroxine, triiodothyronine, and TSH concentrations in 114 patients (mean age 13.6 yr), designated group 1, with thalassaemia major. Forty of these patients were further evaluated (group 2) for serum-free thyroxine, and free and reverse triiodothyronine concentrations. The response of TSH to TRH was measured in 25 patients from this subgroup. Results were compared with those from 53 control subjects. Primary hypothyroidism, defined by a raised TSH level above the upper range limit of 6.5 .mu.IU/ml of the controls, was present in 17.5% of the 114 patients. In group 2 patients, a spectrum of thyroid disease spanning uncompensated and compensated primary hypothyroidism and decreased thyroid reserve was evident. The presence of primary hypothyroidism (uncompensated and compensated) was associated with an age of at least 10 yr, an increased incidence of iron toxicity-related systemic complications, and an increased transfusion iron load but not with an increased serum ferritin level. In the total 114 patients there were 9 who had the low triiodothyronine (sick euthyroid) syndrome. Primary hypothyroidism occurs in a significant proportion of thalassemia major patients in the absence of obvious clinical signs of hypothyroidism; the low triiodothyronine syndrome associated with non-thyroidal disease is not uncommon.

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