Abnormal Glucose Tolerance in β-Thalassemia: Assessment of Risk Factors

Endocrinopathies in beta thalassemia: a narrative review

Beta thalassemia is the most common genetic blood disorder, characterized by reduced production or complete absence of beta-globin chains. The combination of systematic red blood cell transfusion and iron chelation therapy is the most readily available supportive treatment and one that has considerably prolonged the survival of thalassemia patients. Despite this, the development of endocrine abnormalities correlated with beta thalassemia still exists and is mostly associated with iron overload, chronic anemia, and hypoxia. A multifactorial approach has been employed to investigate other factors involved in the pathogenesis of endocrinopathies, including genotype, liver disease, HCV, splenectomy, socioeconomic factors, chelation therapy, and deficiency of elements. The development of specific biomarkers for predicting endocrinopathy risk has been the subject of extensive discussion. The objective of the present narrative review is to present recent data on endocrinopathies in beta thalassemia patients, including the prevalence, the proposed pathogenetic mechanisms, the risk factors, the diagnostic methods applied, and finally the recommended treatment options.

β-Thalassemia and Diabetes Mellitus: Current State and Future Directions

β-Thalassemia major is a congenital hemoglobin disorder that requires regular blood transfusion. The disease is often associated with iron overload and diabetes mellitus, among other complications. Pancreatic iron overload in β-thalassemia patients disrupts β-cell function and insulin secretion and induces insulin resistance. Several risk factors, including family history of diabetes, sedentary lifestyle, obesity, gender, and advanced age increase the risk of diabetes in β-thalassemia patients. Precautionary measures such as blood glucose monitoring, anti-diabetic medications, and healthy living in β-thalassemia patients notwithstanding, the prevalence of diabetes in β-thalassemia patients continues to rise. This review aims to address the relationship between β-thalassemia and diabetes in an attempt to understand how the pathology and management of β-thalassemia precipitate diabetes mellitus. The possible employment of surrogate biomarkers for early prediction and intervention is discussed. More work is still needed to better understand the molecular mechanism(s) underlying the link between β-thalassemia and diabetes and to identify novel prognostic and therapeutic targets.

Endocrinopathies in Hemoglobinopathies: What Is the Role of Iron?

Hemoglobinopathies, including β-thalassemia and sickle cell disease (SCD), are common genetic blood disorders. Endocrine disorders are frequent manifestations of organ damage observed mainly in patients with β-thalassemia and rarely in SCD. Iron overload, oxidative stress-induced cellular damage, chronic anemia, and HCV infection contribute to the development of endocrinopathies in β-thalassemia. The above factors, combined with vaso-occlusive events and microcirculation defects, are crucial for endocrine dysfunction in SCD patients. These endocrinopathies include diabetes mellitus, hypothyroidism, parathyroid dysfunction, gonadal and growth failure, osteoporosis, and adrenal insufficiency, affecting the quality of life of these patients. Thus, we aim to provide current knowledge and data about the epidemiology, pathogenesis, diagnosis, and management of endocrine disorders in β-thalassemia and SCD. We conducted a comprehensive review of the literature and examined the available data, mostly using the PubMed and Medline search engines for original articles. In the era of precision medicine, more studies investigating the potential role of genetic modifiers in the development of endocrinopathies in hemoglobinopathies are essential.

Abdelmotaleb G, Abdel-Azim Eid K, Sebaey S. Mostafa E, Sabry Ahmed E. Evaluation of glycemic abnormalities in children and adolescents with β-thalassemia major

Background

The quality of life of B-thalassemia major (β-TM) patients has improved with the use of frequent blood transfusions. However, this leads to chronic iron overload with its sequelae, as prediabetes and diabetes mellitus. This study aimed to assess insulin resistance and glucose abnormalities in a sample of B-thalassemia major patients in Benha, Egypt.

Results

This case-control study included 40 B-thalassemia major patients on regular blood transfusion and iron chelation. Their ages ranged from 8 to 16 years, and 30 normal age and sex-matched controls. Thorough clinical examination was performed including weight (kg), height (m), body mass index (BMI) (kg/m2), and liver and spleen size. Laboratory investigations were done in the form of complete blood count, liver enzymes, serum ferritin, fasting plasma insulin, and fasting, and 2 h postprandial plasma glucose. Insulin resistance (IR) was calculated using the Homeostasis Model Assessment of insulin resistance (HOMA-IR) index. Insulin resistance was found in 27.5% of thalassemic patients; 18.2% of them had diabetes, 72.7% were prediabetics (with impaired fasting glycemia), and 9.1% had normal fasting and 2 h postprandial plasma glucose level. Insulin resistance increased significantly with increased blood transfusion duration, serum ferritin, liver enzymes, fasting plasma insulin, fasting plasma glucose, and 2 h postprandial plasma glucose (ROC). The curve analysis showed that the duration of blood transfusion, serum ferritin, fasting plasma insulin, fasting, and 2 h postprandial plasma glucose could significantly predict insulin resistance at a certain cut-off point.

Conclusion

Our data show that HOMA-IR can be used to detect insulin resistance in β-TM patients on long-term blood transfusions, especially patients with high serum ferritin and impaired liver enzymes.

Early development of decreased β-cell insulin secretion in children and adolescents with hemoglobin H disease and its relationship with levels of anemia

BACKGROUND

Diabetes mellitus (DM) associated with iron overload has been reported among adults with transfusion-dependent thalassemia and those with non-transfusion-dependent thalassemia (NTDT), especially in β-thalassemia disease. However, little is known about glucose metabolism and how early its dysregulation can develop in α-thalassemia hemoglobin H (Hb H) disease, which is one of the most common types of NTDT worldwide.

PROCEDURE

We prospectively calculated glucose metabolism index in 40 patients (aged 10-25 years) with Hb H disease. Glucose metabolism data were compared between patients with deletional versus nondeletional Hb H, and between patients with normal versus abnormal insulin secretion/sensitivity.

RESULTS

Despite normal glucose tolerance in all patients, 52.5% had abnormal insulinogenic index indicating decreased β-cell insulin secretion. Patients with functional hemoglobin < 8 g/dL had significantly higher percentages of abnormal insulinogenic index. There was no significant difference in abnormal insulinogenic index between deletional and nondeletional Hb H.

CONCLUSION

Decreased β-cell insulin secretion is highly prevalent among children and adolescents with Hb H disease, and it is associated with levels of functional anemia at baseline, but not with the type of Hb H disease. This result warrants heightened awareness among hematologists due to potentially increased risk of DM later in life.

Evaluation of continuous glucose monitoring system for detection of alterations in glucose homeostasis in pediatric patients with β-thalassemia major

BACKGROUND

Disturbances of glucose metabolism are common in β-thalassemia major (β-TM).

AIM

This study was conducted to assess the pattern of glucose homeostasis in pediatric β-TM patients comparing oral glucose tolerance test (OGTT) and continuous glucose monitoring system (CGMS).

METHODS

Two-hundred β-TM patients were studied and those with random blood glucose (RBG) ≥7.8 mmol/L (140 mg/dL) were subjected to OGTT, insertion of CGMS and measurement of fasting C peptide, fasting insulin, and hemoglobin A1c (HbA1c).

RESULTS

Twenty patients (10%) had RBG ≥ 7.8 mmol/L. Using OGTT, 6 out of 20 patients (30%) had impaired glucose tolerance (IGT) while 7 (35%) patients were in the diabetic range. CGMS showed that 7/20 (35%) patients had IGT and 13 (65%) patients had diabetes mellitus (DM); 10 of the latter group had HbA1c readings within diabetic range. The percentage of diabetic patients diagnosed by CGMS was significantly higher than that with OGTT (P = 0.012). Serum ferritin was the only independent variable related to elevated RBG. All β-TM patients with DM were non-compliant to chelation therapy.

CONCLUSIONS

The use of CGMS in the diagnosis of early glycemic abnormalities among pediatric patients with β-TM appears to be superior to other known diagnostic modalities.

Glucose Homeostasis Markers in Beta-Thalassemia

BACKGROUND

Glycosylated hemoglobin (HbA1c) has been a well-recognized marker of glucose homeostasis among thalassemics. Recently some studies have proposed the role of fructosamine as a better marker as compared with HbA1c. Hence, the study was carried out to find out which marker holds promise among Indian beta-thalassemic children.

METHODS

In this case-control study, 60 diagnosed cases of beta-thalassemia major and equal number of normal controls who were ≥8 years of age were enrolled. HbA1c, fructosamine, and fasting insulin levels were measured in all. Oral glucose tolerance test was done as a gold standard and the measured parameters were compared.

RESULTS

HbA1c was significantly higher in cases (7.10% [±0.47%]) than in controls (5.15% [±0.19%]) (P<0.001). Thalassemics with abnormal glucose tolerance had higher HbA1c level (7.34% [±0.57%]) than those with normal glucose tolerance (7.05% [±0.43%]) (P=0.05). Insulin resistance was noticed among thalassemics with abnormal glucose tolerance as compared with their normal counterparts (P=0.04). No significant difference was found in fructosamine levels between cases (239.80 [±31.80] μmol/L) and controls (234.10 [±21.34] μmol/L) (P=0.25) or between thalassemics with abnormal glucose tolerance (243.92 [±21.94] μmol/L) and their normal counterparts (238.77 [±33.93] μmol/L) (P=0.62).

CONCLUSIONS

The use of HbA1c as a diagnostic marker for diabetes in hemolytic anemias has to be done with caution as its baseline values are higher in them. Despite this finding, HbA1c continues to be a good marker for worsening glucose homeostasis in thalassemics as higher values were found in thalassemics with abnormal glucose tolerance compared with their normal counterparts. The present study did not find any relationship of fructosamine levels with impaired glucose tolerance in beta-thalassemia.

Endocrine Complications

More than five decades ago, thalassemia major (TM) was fatal in the first decade of life [...]

Study of Insulin Resistance in Patients With β Thalassemia Major and Validity of Triglyceride Glucose (TYG) Index

Complications like impaired glucose tolerance and diabetes mellitus due to iron overload need early identification in thalassemia. We studied the proportion of insulin resistance in thalassemia major patients on chronic transfusion, identified insulin resistance using homeostasis model assessment of insulin resistance (HOMA-IR) and triglyceride glucose (TYG) index, compared them and validated TYG index. In total, 73 thalassemia patients on regular transfusion for 3 years with serum ferritin >1500 ng/mL were studied. Serum ferritin, fasting blood glucose, triglycerides, and insulin levels were measured, HOMA-IR, and TYG index calculated and analyzed. Mean fasting glucose, triglyceride, and serum insulin values were 104 mg/dL, 164.18 mg/dL, and 19.6 m IU/mL, respectively. Mean serum ferritin was 5156 ng/mL. Insulin resistance was prevalent in one third of thalassemia patients and showed increase with age and serum ferritin. Insulin resistance by HOMA-IR was 32% as against 16% by TYG index with a cut-off value of 4.3. Using receiver operating charecteristic curve analysis, it was found that, by lowering the value of TYG index to 4.0215, sensitivity improved to 78.3% (from 39.13%) with specificity of 70%. Hence, we recommend a newer lower cut-off value of 4.0215 for TYG index for better sensitivity and specificity in identifying insulin resistance.

Glucose Homeostasis and Effect of Chelation on β Cell Function in Children With β-Thalassemia Major

OBJECTIVE

To assess the prevalence of impaired glucose tolerance in β-thalassemia major and correlate it with chelation therapy.

MATERIALS AND METHODS

Sixty-seven subjects with β-thalassemia major, aged 1 to 20 years, were enrolled in our prospective cohort. Clinical details were recorded. Baseline oral glucose tolerance test, serum insulin, C peptide, and insulin resistance were measured. The biochemical profile was repeated after 6 months.

RESULTS

The mean age of subjects was 7.43±4.48 years. Eight (11.9%) subjects had impaired fasting glucose, 7 (10.4%) had impaired glucose tolerance, and 1 (1.4%) subject had diabetes at baseline. Subjects with abnormal glucose profile had longer disease duration (95% confidence interval [CI] of difference=-6.64 to -0.68; P=0.019) and higher fasting blood glucose (95% CI of difference=-32.1 to -10.5; P=0.001) and serum ferritin (95% CI of difference=-219.8 to -3.4; P=0.001) than normoglycemic subjects. Insulin resistance and serum ferritin showed significant increase at 6 months (P<0.001 and P=0.001, respectively). Patients on deferiprone alone significantly improved glucose homeostasis on follow-up than those on desferrioxamine or combination therapy of desferrioxamine and deferiprone (P<0.05).

CONCLUSIONS

Prolonged disease duration and higher serum ferritin adversely affects glucose homeostasis in thalassemic children. Deferiprone was the most effective chelator to improve glucose homeostasis in chronically transfused thalassemics.

Diabetes Mellitus in Thalassaemia Major Patients: A Report from the Southeast of Iran

INTRODUCTION

Diabetes Mellitus (DM) represents a major concern in Thalassaemia Major (TM) patients.

AIM

The present study was conducted to evaluate the frequency of Impaired Fasting Glucose (IFG) and DM in TM patients in Southeast of Iran.

MATERIALS AND METHODS

Fasting Blood Glucose (FBS) was determined using fasting blood samples in 148 TM patients. Demographical data was collected by a questionnaire. Clinical and laboratory variables including cell blood counts, pre-transfusion Haemoglobin (Hb) level, and five-year ferritin were extracted from medical records. Statistical analysis was performed in SPSS19.0 software using chi-square, student t-test and logistic regression.

RESULTS

Females and males comprised 83 (56.1%) and 65 (43.9%) subjects respectively. The mean age and mean five-year ferritin were 17.3±6.1 year-old and 5060.6±2395 ng/ml respectively. Overall, 39 (26.4%) patients had IFG, while 13 (8.8%) were diagnosed with DM. Significant differences were identified in the mean age, volume of transfused blood per occasion, and mean five-years ferritin between the patients with IFG or DM and the patients with normal fasting glucose level. Patients with age >25-year-old had an increased risk of both IFG (OR=4.7,95% CI: 1.3-17, p=0.01) and DM (OR= 7.1, 95% CI: 1-49.2, p=0.04). In addition, splenectomized patients showed a higher risk for IFG (OR=4.3, 95% CI: 1.5-12.1, p=0.005), and ferritin value >6000 ng/ml were associated with an elevated risk of DM (OR=7, 95% CI: 0.8-60.1, p=0.07).

CONCLUSION

Our results indicated that higher age, mean five-years ferritin, volume of blood transfused per occasion, as well as splenectomy were risk factors of IFG and DM in TM patients.

T2* Magnetic Resonance Imaging Study of Pancreatic Iron Overload and its Relation With the Diabetic State in Thalassemic Patients

The present study was performed to evaluate pancreatic hemosiderosis by means of magnetic resonance imaging (MRI) T2* and its relation to the diabetic state in thalassemic patients. One hundred thirty transfusion-dependent thalassemic patients from Zafar adult thalassemia clinic, Tehran, Iran, were enrolled in the study. Data such as age, type of thalassemia, age at diagnosis, transfusion duration, ferritin level, and fasting blood sugar results were gathered. Pancreatic MRI T2* was performed for all patients. One hundred four thalassemic patients with no sign of diabetes mellitus and 26 thalassemic patients with diabetes mellitus entered the study. Out of a total of 130 patients, 102 had pancreatic hemosiderosis. Among them, 23 of 26 diabetic patients (88.5%) and 79 of 104 nondiabetic patients (76%) showed pancreatic hemosiderosis, indicating no statistically significant difference between the 2 groups. The mean pancreatic MRI T2* relaxation time for all patients was 13.99±12.43 ms. The mean relaxation was 13.62±8.38 and 14.08±13.28 ms for diabetic and nondiabetic patients, respectively, showing no statistical difference (P=0.202). In conclusion, we did not find a significant difference between diabetic and nondiabetic thalassemic patients regarding the MRI T2* relaxation time readings or the rate of pancreatic hemosiderosis. We recommend performing studies with a higher sample size and including patients from different age groups to further evaluate the role of T2* MRI of pancreatic iron overload and its relation with the diabetic state in thalassemic patients.

The ICET-A Recommendations for the Diagnosis and Management of Disturbances of Glucose Homeostasis in Thalassemia Major Patients

Iron overload in patients with thalassemia major (TM) affects glucose regulation and is mediated by several mechanisms. The pathogenesis of glycaemic abnormalities in TM is complex and multifactorial. It has been predominantly attributed to a combination of reduced insulin secretory capacity and insulin resistance. The exact mechanisms responsible for progression from norm glycaemia to overt diabetes in these patients are still poorly understood but are attributed mainly to insulin deficiency resulting from the toxic effects of iron deposited in the pancreas and insulin resistance. A group of endocrinologists, haematologists and paediatricians, members of the International Network of Clinicians for Endocrinopathies in Thalassemia and Adolescence Medicine (ICET-A) convened to formulate recommendations for the diagnosis and management of abnormalities of glucose homeostasis in thalassemia major patients on the basis of available evidence from clinical and laboratory data and consensus practice. The results of their work and discussions are described in this article.

Effect of long-term transfusion therapy on the glycometabolic status and pancreatic Beta cell function in patients with Beta thalassemia major

BACKGROUND

Diabetes mellitus is a major complication of iron overload in patients with beta thalassemia major.

DESIGN

This is a descriptive study conducted in a Tertiary Care Teaching Hospital to analyze beta cell function and insulin resistance, and their relation to iron overload status in beta thalassemia major. Fasting glucose, two-hour post load glucose, fasting insulin, alanine amino transaminase (ALT), and ferritin were used as outcome measures. The homeostatic model assessment (HOMA model) was used to calculate the beta cell function and insulin resistance index.

RESULTS

Of the 30 cases, 20% had impaired fasting glucose, 3.3% had impaired glucose tolerance, and none had diabetes. Fasting glucose was not significant between the cases and controls (P = 0.113). Fasting insulin (P = 0.001), ferritin (P = 0.001), and ALT (P = 0.001) levels were significantly high in the cases. Insulin resistance index was significantly higher in the cases (P = 0.001) as also the beta cell function (P = 0.001). With increase in age and the number of units transfused there is a decline in beta cell function, fasting insulin, and insulin resistance after attaining the maximum level. This suggests that initial insulin resistance is followed by insulin depletion due to loss of beta cell function, leading to diabetes mellitus.

CONCLUSION

Impaired glucose tolerance (IGT) and insulin resistance precede the onset of insulin-dependent diabetes and adequate chelation therapy is essential for delaying the onset or for prevention of diabetes.

Pancreatic iron and glucose dysregulation in thalassemia major

Pancreatic iron overload and diabetes mellitus (DM) are common in thalassemia major patients. However, the relationship between iron stores and glucose disturbances is not well defined. We used a frequently sampled oral glucose tolerance test (OGTT), coupled with mathematical modeling, and magnetic resonance imaging (MRI) to examine the impact of pancreatic, cardiac, and hepatic iron overload on glucose regulation in 59 patients with thalassemia major. According to OGTT results, 11 patients had DM, 12 had impaired glucose tolerance (IGT), 8 had isolated impaired fasting glucose (IFG), and 28 patients had normal glucose tolerance (NGT). Patients with DM had significantly impaired insulin sensitivity and insulin release. Insulin resistance was most strongly associated with markers of inflammation and somatic iron overload, while disposition index (DI) (a measure of beta cell function) was most strongly correlated with pancreas R2*. Patients with DM and IGT had significantly worse DI than those with NGT or IFG, suggesting significant beta cell toxicity. One-third of patients having elevated pancreas R2* had normal glucose regulation (preclinical iron burden), but these patients were younger and had lower hepatic iron burdens. Our study indicates that pancreatic iron is the strongest predictor of beta cell toxicity, but total body iron burden, age, and body habitus also influence glucose regulation. We also demonstrate that MRI and fasting glucose/insulin are complementary screening tools, reducing the need for oral glucose tolerance testing, and identify high-risk patients before irreversible pancreatic damage.

Gradient-echo magnetic resonance imaging study of pancreatic iron overload in young Egyptian beta-thalassemia major patients and effect of splenectomy

BACKGROUND

Thalassemic patients suffer from diabetes mellitus secondary to hemosiderosis.

AIMS

The study aimed to evaluate pancreatic iron overload by T2*-weighted Gradient-echo magnetic resonance imaging (MRI) in young beta-thalassemia major patients and to correlate it with glucose disturbances, hepatic hemosiderosis, serum ferritin and splenectomy.

METHODS

Forty thalassemic patients (20 non diabetic, 10 diabetic, and 10 with impaired glucose tolerance) were recruited from Pediatric Hematology Clinic, in addition to 20 healthy controls. All patients underwent clinical assessment and laboratory investigations included complete blood count, liver function tests, serum ferritin and oral glucose tolerance test (OGTT). A T2*-weighted gradient-echo sequence MRI was performed with 1.5 T scanner and signal intensity ratio (SIR) of the liver and the pancreas to noise were calculated.

RESULTS

Significant reduction in signal intensity ratio (SIR) of the liver and the pancreas was shown in thalassemic patients compared to controls (P < 0.0001), Thalassemic patients with abnormal glucose tolerance; including diabetics and thalassemics with impaired glucose tolerance; displayed a higher degree of pancreatic and hepatic siderosis compared to thalassemics with normal glucose tolerance or controls (P < 0.001, P < 0.0001). Splenectomized thalassemic patients had significantly lower SIR of pancreas compared to non splenectomized patients (P < 0.05). A strong correlation was present between hepatic and pancreatic siderosis in studied patients (P < 0.001).

CONCLUSIONS

pancreatic siderosis can be detected by T2* gradient-echo MRI since childhood in thalassemic patients, and is more evident in patients with abnormal glucose tolerance. After splenectomy, iron deposition may be accelerated in the pancreas. Follow up of thalassemic patients using pancreatic MRI together with intensive chelation therapy may help to prevent the development of overt diabetes.