The pituitary–adrenal axis in adult thalassaemic patients

Abstract

We previously described in young thalassaemic patients an altered cortisol and ACTH responsiveness suggesting an impaired adrenocortical reserve. Owing to iron overload, a worsening of adrenal function should be expected in adult patients. In 124 adults with beta-thalassaemia, urinary free cortisol (UFC) and plasma ACTH levels were determined and compared with those measured in 150 controls. In 45 patients, cortisol was measured in response to: i) tetracosactide 1 microg as an i.v. bolus (low-dose test, LDT) and ii) tetracosactide 250 microg infused i.v. over 8 h (high-dose test, HDT). UFC and serum cortisol were within the reference range in all patients. Conversely, basal plasma ACTH values were above the upper limit of the normal range in 19 patients. There were no statistically significant differences in the mean values of UFC, basal serum cortisol and plasma ACTH between patients and controls. A subnormal cortisol response to the LDT was registered in 18 out of 56 patients. Three of these patients also displayed a subnormal response to the HDT, together with elevated baseline plasma ACTH levels. In the LDT, a positive correlation was found between basal and peak cortisol values (P<0.0001). The latter were negatively correlated with basal ACTH values in both LDT (P<0.0001) and HDT (P<0.0001). Adult thalassaemic patients often present a subtle impairment of adrenocortical function. This may become clinically relevant in case of major stressful events. Thus, we recommend an assessment of adrenocortical function in all adult thalassaemic patients.