Longitudinal Changes in Endocrine Disease in Thalassemia Major Patients on Different Iron Chelators

Introduction: Endocrinopathies are common in regularly transfused patients with β-thalassemia major (TM). Damage may start in childhood with the incidence of overt endocrine complications increasing with advancing age, making it essential to introduce appropriate intervention promptly to prevent the development of later morbidity. Iron overload has been consistently linked with the development of endocrine disease in TM. However, data on the role of iron chelation therapy for the prevention or management of endocrine disease, especially in the long-term, remain limited.

Methods: We conducted a retrospective cohort study of all TM patients attending our center that have remained on the same chelation therapy for a minimum of 5 years. For all patients demographic data at the start of observation, type of chelator, and mean serum ferritin (SF) across the 5 year period were collected. A single endocrinologist evaluated the patients at the start and end of observation after 5 years to assess for the presence and absence of endocrinopathies as locally defined through clinical and laboratory values including: diabetes mellitus (DM), hypothyroidism, and hypogonadism.

Results: A total of 165 patients were included in the analysis. Their mean age was 39.9 ± 8.3 years (range: 20-68), including 71 (43%) men. The mean SF value was 555 ng/mL (range: 63-6140).Deferoxmiane (DFO) was used in 40 (24.2%) patients, deferiprone (DFP) in 18 (10.9%), DFO+DFP in 50 (30.3%) and deferasirox (DFX) in 57 (34.5%). At the start of observation, 121 (73.3%) of patients had at least one of the three endocrinopathies (51 [31.5%] had two endocrinpathies and 8 [4.8%] had all three). After 5 years of chelation therapy, 6 patients (3.6%) had reversal of at least one existing endocrinopathy, 11 (6.7%) had the development of at least one additional endocrinopathy, and 148 (89.7%) had no change in the number of their endocrinopathies. Figure 1 illustrates the reversal of existing or development of new endocirnopathy between iron chelators. Patients on DFX had the lowest proportion of patients with the development of a new endocrinopathy and the highest proportion of patients with reversal of existing endocrinopathy. On a receiver operating characteristic curve analysis a SF level of <600 ng/mL was the best predictor for patients not developing new endocrinopathy (p=0.018).

Conclusions: Our data confirmed that patients with TM experience a high prevalence of endocrine disease. Iron chelation therapy, however, has a role in preventing the development of new endocrine disease and in a minority of patients, reversal of existing endocrinopathy. These effects may be dependent on the chelator type although achieving levels <600 ng/mL should prevent newly incident disease.