In this study, the mean age range was 12.3 ± 2.8 years, which was not significantly different from other studies [17]. Based on the analysis, the baseline data might be considered a general characteristic among thalassemia majors aged 6–18 years in Indonesia as approximately 30% of patients originated from provinces other than their current location.

Subjects between the ages of 6 to 10 years may be suitable for the MRIT2* procedure without sedation. This procedure is mainly recommended for individuals over 8 years of age [18, 19]. The MRIT2* examination is suggested at the age of 6, while LGE (late gadolinium enhancement) is recommended at 13 years of age [20]. In this study, patients who had ferritin levels > 1000 ng/m were recruited, as this condition often accompanies left ventricular dilatation, tricuspid regurgitation, and pulmonary hypertension [21].

The following variables, Hb, Ret-He, HIF-1, IG, hs-CRP, IL-6, ferritin, and transferrin saturation, were included in the SEM model analysis to determine their interaction with hepcidin release. The mean Hb level was 9.2 ± 1.2 g/dL, indicating the absence of severe anemia, which can lead to hepcidin deficiency. This explains the lack of a relationship between Hb and hepcidin. Furthermore, severe anemia and depleted hepcidin can lead to the accumulation of iron in hepatic parenchymal tissue [9].

We found 19 subjects, accounting for 24%, with an upper normal limit of reticulocyte. A significant correlation was observed between reticulocytes (r = − 0.43, p = 0.01) and Ret-He with ferritin (r = 0.29, p = 0.01). This is consistent with the increased reticulocyte reflects increased erythropoiesis [22].

A total of 9 subjects (11.25%) had a white blood count of > 10,000/µL and 14.8% had upper normal IL-6 value with no sign of infection. Based on normal clinical results, 10 subjects, accounting for 12.5% had thrombocytopenia, which is caused by hypersplenism, use of DFP, increased platelet destructions, and reduced thrombopoietin. Furthermore, elongated PT and aPTT are more often present in subjects whose hepatic iron deposits are within a moderate-severe degree compared to a normal-mild degree [23].

The increase of AST, ALT, SI, and TIBC is consistent with the results of other studies. Furthermore, a correlation was observed between AST and ferritin (r = 0.27, p = 0.02), and the increase in AST and ALT have significantly higher ferritin than subjects with normal AST and ALT (p = 0.01) [24].

The level of hepcidin is not significantly different from the result of a study by Jagadishkumar using Cloud Clown Corp reagent [25]. In this study, a deficiency of hepcidin was observed in 37.5% of the subjects. Additionally, the hepcidin-ferritin ratio indicated a deficiency of hepcidin in all subjects. This result suggests that the hepcidin-ferritin ratio was unable to increase alongside ferritin. A Low hepcidin-to-ferritin ratio indicates post-transfusion partial erythropoiesis correction [26].

The homeostasis of hepcidin remains unclear, and several studies have shown contradicting results [7]. The expression of hepcidin is intricate and involves the coordination of interacting release variables [7, 8]. A previous study showed that subjects with transfusion-related iron deposits had a varying hepcidin increase [15]. Lower hepcidin level on thalassemia variants has a characteristic of decreased Ret-He [27]. In animals, hepcidin regulation occurs due to a single stimulation, but it is complex with unknown precipitating factors in humans. Furthermore, no correlation was found between ferritin and MRIT2* (r = − 0.21 p = 0.06), which is consistent with the report of another study [28].

In this study, hepcidin was found to be negatively correlated with hs-CRP, which contradicts previous studies [28, 29]. Hepcidin increased in normal subjects, due to infection, inflammation, and increased liver iron. Parischa et al. [28] reported no correlation between Hepcidin and CRP, while Ganz et al. [29] suggested increased hepcidin levels in subjects whose CRP level is > 10 mg/dL. Iron accumulation increases ROS and ROS, which is associated with inflammation and is primarily caused by ROS [30]. The decline of hepcidin resulted in increased ROS, triggering an increase in IL-6.

One of the variables that have a direct role in MRIT2* is Ret-He. Higher reticulocyte represents higher erythropoiesis activities, reducing hepcidin and affecting myocardial iron deposits. Conversely, hb is a variable that is directly correlated with ST2. A previous study showed that myocardial injury is caused by abnormal perfusion, genetic disorder, and an increase in volume and pressure [31].

Neither hs-CRP nor IL-6 plays a direct role in hepcidin, but they have a combined effect on hepcidin levels. A plausible explanation would consider hepcidin as an acute-phase reactant, where infection/inflammation stimulates the formation of IL-6 [32]. In return, IL-6 strongly correlated with hs-CRP, but these two variables do not play a direct role in MRIT2*. This is because the myocardial iron deposit received much influence from NTBI due to iron deposition overload rather than infection or inflammation.

The mechanism of myocardial fibrosis is very complex and relates to angiotensin II, TGF-β, Smard3/4, endothelin-1, extracellular matrix (ECM) protein, and interleukins such as IL-13, IL-14, IL-10, IL-4, TNF α [32, 33].

Currently, there is a lack of published studies exploring the involvement of hs-CRP and IL-6 in myocardial fibrosis in thalassemia. Some of the factors affecting myocardial fibrosis are cytokines, such as IL-6, IL-1β, TNFα, MCP-1, TGF-β, angiotensin II, angiotensin II type I, and ECM [34].

The combined effect, which plays a role in MRIT2* is Ret-He and transferrin. These results collaborate with the theory stating that periodic transfusion in anemia increases ferritin, transferrin, NTBI, iron deposit, and cardiac iron overload. In previous studies, there was no correlation between MRIT2* and ST2, and this result is consistent with other studies showing no significant relationship between fibrosis with LGE nor MRIT2* [35, 36].

The variables with the strongest association with ST2 are hs-CRP, transferrin saturation, and Hb. Increasing ST2 is associated with myocardial fibrosis. ST2 is an IL-1 and IL-33 member, influenced by inflammation. CRP was positively correlated with an increase in ST2 and severe cardiac fibrosis [37]. Increased levels of IL-6 and CRP are associated with myocardial fibrosis [33]. Furthermore, the combined effects that played a role in hepcidin were hs-CRP and IL-6. This is consistent with the report of previous studies that there was an increase in hs-CRP, IL-6, IL-8, and TNFα in thalassemia major. Increased hepcidin decreases the production of ROS, reducing inflammation [38].