Pituitary iron and volume predict hypogonadism in transfusional iron overload.

Hypogonadism is the most common morbidity in patients with transfusion-dependent anemias such as thalassemia major. We used magnetic resonance imaging (MRI) to measure pituitary R2 (iron) and volume to determine at what age these patients develop pituitary iron overload and volume loss. We recruited 56 patients (47 with thalassemia major, five with chronically transfused thalassemia intermedia and four with Blackfan-Diamond syndrome) to have pituitary MRIs to measure pituitary R2 and volume. Hypogonadism was defined clinically based on the timing of secondary sexual characteristics or the need for sex hormone replacement therapy. Patients with transfusional iron overload begin to develop pituitary iron overload in the first decade of life; however, clinically significant volume loss was not observed until the second decade of life. Severe pituitary iron deposition (Z > 5) and volume loss (Z < -2.5) were independently predictive of hypogonadism. Pituitary R2 correlated significantly with serum ferritin as well as liver, pancreatic, and cardiac iron deposition by MRI. Log pancreas R2* was the best single predictor for pituitary iron, with an area under the receiving operator characteristic curve of 0.88, but log cardiac R2* and ferritin were retained on multivariate regression with a combined r(2) of 0.71. Pituitary iron overload and volume loss were independently predictive of hypogonadism. Many patients with moderate-to-severe pituitary iron overload retained normal gland volume and function, representing a potential therapeutic window. The subset of hypogonadal patients having preserved gland volumes may also explain improvements in pituitary function observed following intensive chelation therapy.

Predicting pituitary iron and endocrine dysfunction.

Patients with thalassemia major (TM) require lifelong transfusion therapy to survive, leading to toxic iron overload in the endocrine glands and heart. The pituitary gland is one of the most vulnerable targets, leading to irreversible hypogonadotropic hypogonadism in approximately half of patients. Improvements in magnetic resonance imaging (MRI) technology and understanding have allowed earlier recognition of preclinical iron deposition in the heart, pancreas, and liver; prior work also supports a similar role for the pituitary. The purpose of this study is threefold, (1) to develop age-specific nomograms for pituitary iron and volume metrics; (2) to determine the prevalence, severity, and age of onset of pituitary iron deposition and volume loss in TM patients, and (3) to determine whether deferasirox monotherapy can modify the trajectory of pituitary iron accumulation and damage over a two-year period. This article outlines relevant background studies and methodological details as well as providing preliminary results from our first two aims.