Pituitary Volume and Iron Overload Evaluation by 3T MRI in Thalassemia.

OBJECTIVE

To evaluate pituitary volume and iron overload in beta thalassemia major, with the objective of assessing the reliability of this method in predicting hypogonadism.

METHODS

3T MRI was used to measure pituitary R2 and T2* in 57 beta thalassemia major patients and 30 controls. Anterior pituitary volume was evaluated by MRI planimetry. Cardiac, hepatic, and pancreatic iron overload were also assessed using MRI T2*. Mean serum ferritin was estimated by sandwich immuno-assay. Short stature was defined as height < 3 rd percentile for age, and clinical hypogonadism defined as absence of secondary sexual characteristics at ages ≥ 13 y for females and ≥ 14 y for males.

RESULTS

Short stature was present in 32 patients (56.1%). Of the 47 patients in the pubertal age group, 11(23.4%) had hypogonadism. Serum ferritin correlated positively with pituitary R2 (p = 0.004) and negatively with anterior pituitary volume (p = 0.006), whereas pituitary R2 correlated negatively with cardiac T2* (p = 0.001). Patients with hypogonadism had lower pituitary R2 (p = 0.186), T2* (p = 0.048), and anterior pituitary volumes (p = 0.012) compared to those with normal sexual maturity. Regardless of stature, no significant difference was observed between pituitary R2 (p = 0.267) and T2* (p = 0.451). Mean pituitary R2 in patients (78.99 Hz) was higher than in controls (20.8 Hz) (p = 0.0001). Anterior pituitary volume was lower in patients (264.83 mm3) than in controls (380.87 mm3) (p = 0.0001). A threshold value of 22.85 Hz for pituitary R2 gave a sensitivity of 84.2% and a specificity of 73.3% in distinguishing pituitary iron content of patients from controls, with an area of 0.864 under the ROC curve.

CONCLUSIONS

3T MRI is a reliable method to detect pituitary iron overload and predict risk of hypogonadism in beta Thalassemia.