It is well-known that repeated blood transfusions in beta-thalassemia major cause iron overload in vital organs like endocrine organs, heart, liver, and lungs leading to delayed puberty, defective vitamin D synthesis, cardiac dysfunction, pulmonary dysfunction, hypertension, and restrictive lung disease.

Cardiomyopathy due to iron overload is the leading cause of death in chronic transfusion therapy patients [10]. Echocardiographic evidence of ventricular diastolic dysfunction can be detected earlier before systolic dysfunction occurs, using tissue Doppler signals [6, 11]. The present study was designed with this background to assess the association between vitamin D and left ventricular function in thalassemia major with iron overload. The subjects were above 5 years old and with more than 2500 ng/ml serum ferritin. The mean age of the study population was 10.24 + 3.56 years, which is in concordance with the other Indian studies [12, 13]. It also corresponds to another study on thalassemia majors from our institution, where the mean age group is 12.27 ± 4.18 years. Other studies from various populations had a higher mean age [12, 14].

In this study, the mean ferritin level was 4622 ± 2289.87 ng/ml, which is well over 2500 ng/ml, which is associated with an increased risk of cardiac dysfunction. It has been previously reported by Anderson et al. that ferritin levels > 2500 mg/l increased the risk of cardiac dysfunction [15]. After the introduction of chelating agents, the occurrence of heart failure shifted to the second decade. The mean age of our subjects is 10.2 ± 3.56 years; therefore, left ventricular ejection fraction (LVEF) and fractional shortening (FS) were still within normal limits but would begin to decrease as the adolescents would get older.

Vitamin D suppresses tumor necrosis factor α (TNF-α) release and increases interleukin-10 (IL-10) synthesis. Raised inflammatory cytokines like TNF-α and deficient IL-10 lead to severe atherosclerosis. Schleithoff et al. found that compared to placebo, parathyroid hormone levels (PTH) were significantly lower in congestive heart failure (CHF) patients with vitamin D supplementation [16]. IL-10, an anti-inflammatory cytokine, was increased after vitamin D supplementation, and pro-inflammatory cytokine TNF-α remained static in the vitamin D supplementation group. It was raised in the placebo group [16].

In this study, 31 (44.3%) children with thalassemia major had vitamin D deficiency (< 20 ng/mL). These results were consistent with a study by Fadhillah et al. that stated there was vitamin D deficiency in 85.5% of thalassemia children in Hasan Sadikin Hospital [17]. Wood et al. also found vitamin D deficiency occurred in 55.4% of patients with thalassemia [18]. Dipankar Hazarika et al. showed 52% vitamin D deficiency in thalassemia patients [19]. Dhale et al. showed that 77.7% of thalassemia patients had vitamin D levels lower than required [20]. Vitamin D deficiency was present in 82% of the thalassemia patients in contrast to 47% of the standard controls in a study conducted by Akhouri et al. in 2017 [2]. 25-OH-vitamin D deficiency was observed in 98% of the study group of thalassemia patients and 68% in the control group in the Agrawal et al. study in 2016 [3]. Ahmed in 2019 compared vitamin D levels in thalassemia patients (13.12 ± 2.90 ng/ml) with standard values of vitamin D (24.2 ± 4.1 ng/ml) in India among the pediatric population [21]. Iron deposition in the liver and skin of patients with thalassemia major disrupts hydroxylation and synthesis of vitamin D, so most of the patients with thalassemia major have vitamin D deficiency.

No significant correlation was found between age and vitamin D in our study. These results concord with the earlier study by Ambarwati et al. in Indonesia [22]. There is a statistically significant negative correlation between vitamin D levels and serum ferritin. These results were consistent with the findings of Wood et al., who had observed a negative correlation between vitamin D and ferritin levels among thalassemia children [18].

In our study, 2D echocardiography is used to estimate the function of left ventricular function. In a study by Koohi et al., diastolic dysfunction (34%) was the most common echocardiography disorder, while the systolic dysfunction prevalence estimated was about 9% [23]. Davis et al. found that left ventricular diastolic dysfunction develops early, but the systolic dysfunction determines the outcome in these patients, and most die of systolic dysfunction [24].

The results of this study showed a significant positive association between levels of vitamin D and left ventricular function as represented by EF (p = 0.018) and FS (p = 0.014). This result was consistent with a previous study by Wood that states a correlation between vitamin D levels and LVEF [25]. Low vitamin D levels increase parathyroid hormone production, increasing heart rate. It also disturbs the contraction of cardiomyocytes and increases natriuretic peptide secretion, which may lead to cardiac hypertrophy [26, 27]. Therapy with an active vitamin D analog reduces left atrial hypertrophy and attenuates the rise of BNP [28].

A longitudinal prospective analysis is required to observe the improvement of cardiac function after vitamin D supplementation and chelation in beta-thalassemia children with iron overload. Although this study identified significant associations between vitamin D levels and cardiac status, a longitudinal follow-up was not done. Further studies are required to determine the adequate dose of vitamin D to prevent overload and improve cardiac function. It would help establish standard guidelines for vitamin D supplementation in all beta-thalassemia children.