Endocrine Abstracts

Background: β-thalassemia is associated with increased iron overload in endocrine tissues, including parathyroid glands. The occurrence of unbalanced calcium (Ca)-phosphorous (P) metabolism, such as chronic HPT, is higher in these patients compared to the general population. However, data about prevalence and presentation of HPT in this setting are scanty.

Aim: To explore the biochemical characteristics of Ca-P metabolism, particularly the prevalence of hypoparathyroidism, in adult patients with β-thalassemia major and intermedia compared to healthy subjects.

Methods: Single-center, retrospective, case-control study, including 34 patients with β-thalassemia and 57 age-matched controls. The main outcome measures were serum Ca, P, Ca/P ratio, intact parathyroid hormone (PTH), albumin, and creatinine. Primary hypoparathyroidism (pHPT) was defined as hypocalcemia with low/inappropriately normal PTH, whereas subclinical hypoparathyroidism (sHPT) as serum Ca at the lower limit of normal range with low PTH.

Results: Serum P was higher in patients with β-thalassemia compared to controls (3.8±0.6 mg/dL vs 3.5±0.6 mg/dL, P = 0.008), whereas no difference was found for serum Ca. The Ca/P ratio was lower in the β-thalassemia compared to controls (2.48±0.42 vs 2.77±0.42, P = 0.002), as well as serum PTH (22.4±10.9 pg/mL vs 34.1±14.1 pg/mL, P < 0.001). No difference was found for serum albumin between groups. A Ca/P ratio <2.3, that is suggestive for unbalanced Ca-P metabolism, was found in 14 out of 34 patients (41.1%) and in 8 out of 57 controls (14.0%). Focusing on β-thalassemic patients, pHPT was observed in 3 patients (8.8%) and sHPT in 22 (64.7%) without difference between major and intermedia forms.

Conclusions: Despite of a low prevalence of overt pHPT, the non-classical phenotype sHPT is a common finding in patients with β-thalassemia. A periodic evaluation of serum Ca and P should be included in the follow-up of these patients to early detect an unbalanced mineral metabolism.