Link between Genotype and Multi-Organ Iron and Complications in Children with Transfusion-Dependent Thalassemia

Genetic Correlation of HBB, HFE and HAMP Genes to Endocrinal Complications in Egyptian Beta Thalassemia Major Patients

Iron loading is regarded as the primary cause of endocrine abnormalities in thalassemia major patients. Thus, the purpose of the current research was to explore the impact of thalassemia genotypes, hepcidin antimicrobial peptide (HAMP) and hereditary hemochromatosis (HFE) gene variants, and hepcidin expression on serum ferritin and endocrinal complications in thalassemia patients. The study comprised fifty beta-thalassemia cases and fifty age- and sex-matched controls. Genotyping of the Beta-globin gene (HBB), HAMP, and exon 2 of the HFE gene was performed using Sanger sequencing. C282Y (c.845G > A) variant of the HFE gene was determined by PCR-RFLP. Hepcidin mRNA expression was assessed by qRT-PCR. Biochemical and hormonal studies were done for all patients. Hypogonadism and short stature were found in 56% and 20% of the investigated cases, respectively. Molecular studies reported a statistically higher frequency of the HAMP variant c.-582A > G in thalassemic patients than controls. Significant downregulation of hepcidin expression was found in cases compared to healthy subjects that was significantly associated with short stature. Considering the thalassemia alleles, the IVSI.1G > A (β0) allele was statistically related to hypogonadism. Our results proposed that thalassemia genotypes and downregulated hepcidin expression were the potential risk factors for endocrinopathies in our cases. We also demonstrated an increased incidence of the HAMP promoter variant c.- 582A > G that might have a role in the pathogenesis of iron overload in thalassemic cases. Significant downregulation of hepcidin expression, that contributes to increased iron burden, could be used as a future therapeutic target in these patients.

Impact of genotype on multi-organ iron and complications in patients with non-transfusion-dependent β-thalassemia intermedia

We evaluated the impact of the genotype on clinical and hematochemical features, hepatic and cardiac iron levels, and endocrine, hepatic, and cardiovascular complications in non-transfusion-dependent (NTD) β-thalassemia intermedia (TI) patients. Sixty patients (39.09 ± 11.11 years, 29 females) consecutively enrolled in the Myocardial Iron Overload in Thalassemia project underwent Magnetic Resonance Imaging to quantify iron overload, biventricular function parameters, and atrial areas and to detect replacement myocardial fibrosis. Three groups of patients were identified: homozygous β+ (N = 18), heterozygous β0β+ (N = 22), and homozygous β0 (N = 20). The groups were homogeneous for sex, age, splenectomy, hematochemical parameters, chelation therapy, and iron levels. The homozygous β° genotype was associated with significantly higher biventricular end-diastolic and end-systolic volume indexes and bi-atrial area indexes. No difference was detected in biventricular ejection fractions or myocardial fibrosis. Extramedullary hematopoiesis and leg ulcers were significantly more frequent in the homozygous β° group compared to the homozygous β+ group. No association was detected between genotype and liver cirrhosis, hypogonadism, hypothyroidism, osteoporosis, heart failure, arrhythmias, and pulmonary hypertension. Heart remodelling related to a high cardiac output state cardiomyopathy, extramedullary hematopoiesis, and leg ulcers were more pronounced in patients with the homozygous β° genotype compared to the other genotypes analyzed. The knowledge of the genotype can assist in the clinical management of NTD β-TI patients.

Pancreatic iron in pediatric transfusion-dependent beta-thalassemia patients: A longitudinal MRI study

BACKGROUND

In pediatric transfusion-dependent thalassemia (TDT) patients, we evaluated the prevalence, pattern, and clinical associations of pancreatic siderosis and the changes in pancreatic iron levels and their association with baseline and changes in total body iron balance.

PROCEDURE

We considered 86 pediatric TDT patients consecutively enrolled in the Extension-Myocardial Iron Overload in Thalassemia Network. Iron overload (IO) was quantified by R2* magnetic resonance imaging (MRI).

RESULTS

Sixty-three (73%) patients had pancreatic IO (R2* > 38 Hz). Global pancreas R2* values were significantly correlated with mean serum ferritin levels, MRI liver iron concentration (LIC) values, and global heart R2* values. Global pancreas R2* values were significantly higher in patients with altered versus normal glucose metabolism. Thirty-one patients also performed the follow-up MRI at 18 ± 3 months. Higher pancreatic R2* values were detected at the follow-up, but the difference versus the baseline MRI was not significant. The 20% of patients with baseline pancreatic IO showed no pancreatic IO at the follow-up. The 46% of patients without baseline pancreatic IO developed pancreatic siderosis. The changes in global pancreas R2* between the two MRIs were not correlated with baseline serum ferritin levels, baseline, final, and changes in MRI LIC values, or baseline pancreatic iron levels.

CONCLUSIONS

In children with TDT, pancreatic siderosis is a frequent finding associated with hepatic siderosis and represents a risk factor for myocardial siderosis and alterations of glucose metabolism. Iron removal from the pancreas is exceptionally challenging and independent from hepatic iron status.

Recent advancements in glucose dysregulation and pharmacological management of osteoporosis in transfusion-dependent thalassemia (TDT): an update of ICET-A (International Network of Clinicians for Endocrinopathies in Thalassemia and Adolescence Medicine)

PURPOSE OF REVIEW

The aim of this short review is to provide an update on glucose homeostasis, insulin secretion and pharmacological management of osteoporosis in transfusion-dependent thalassemia (TDT).

RECENT FINDINGS

A retrospective study, documenting the changes in glucose-insulin homeostasis from early childhood to young adulthood, has advanced our understanding of the evolution of glucose regulation in patients with TDT. Magnetic Resonance Imaging (T2* MRI) is considered to be a reliable tool to measure pancreatic iron overload. Continuous glucose monitoring systems (CGMS) can be used in early diagnosis of glucose dysregulation and in disease management in patients with already diagnosed diabetes. Oral glucose-lowering agents (GLAs) are effective and safe for the treatment of diabetes mellitus (DM) in patients with TDT, achieving adequate glycemic control for a substantial period of time. Current modalities for the management of osteoporosis in adults with TDT include inhibitors of bone remodeling such as bisphosphonates and denosumab as well as stimulators of bone formation (e.g., teriparatide), Considering the unique characteristics of osteoporosis associated with TDT, early diagnosis, treatment initiation and treatment duration are critical issues in the management this special population.

CONCLUSIONS

Advances in the care of TDT patients  have led to improved survival and quality of life. Nevertheless, many chronic endocrine complications still remain. Their routine screening and a high index of suspicion are imperative in order to provide timely diagnosis and  treatment.

New Entity-Thalassemic Endocrine Disease: Major Beta-Thalassemia and Endocrine Involvement

Beta-thalassemia (BTH), a recessively inherited haemoglobin (Hb) disorder, causes iron overload (IO), extra-medullary haematopoiesis and bone marrow expansion with major clinical impact. The main objective of this review is to address endocrine components (including aspects of reproductive health as fertility potential and pregnancy outcome) in major beta-thalassemia patients, a complex panel known as thalassemic endocrine disease (TED). We included English, full-text articles based on PubMed research (January 2017–June 2022). TED includes hypogonadism (hypoGn), anomalies of GH/IGF1 axes with growth retardation, hypothyroidism (hypoT), hypoparathyroidism (hypoPT), glucose profile anomalies, adrenal insufficiency, reduced bone mineral density (BMD), and deterioration of microarchitecture with increased fracture risk (FR). The prevalence of each ED varies with population, criteria of definition, etc. At least one out of every three to four children below the age of 12 y have one ED. ED correlates with ferritin and poor compliance to therapy, but not all studies agree. Up to 86% of the adult population is affected by an ED. Age is a positive linear predictor for ED. Low IGF1 is found in 95% of the population with GH deficiency (GHD), but also in 93.6% of persons without GHD. HypoT is mostly pituitary-related; it is not clinically manifested in the majority of cases, hence the importance of TSH/FT4 screening. HypoT is found at any age, with the prevalence varying between 8.3% and 30%. Non-compliance to chelation increases the risk of hypoT, yet not all studies confirmed the correlation with chelation history (reversible hypoT under chelation is reported). The pitfalls of TSH interpretation due to hypophyseal IO should be taken into consideration. HypoPT prevalence varies from 6.66% (below the age of 12) to a maximum of 40% (depending on the study). Serum ferritin might act as a stimulator of FGF23. Associated hypocalcaemia transitions from asymptomatic to severe manifestations. HypoPT is mostly found in association with growth retardation and hypoGn. TED-associated adrenal dysfunction is typically mild; an index of suspicion should be considered due to potential life-threatening complications. Periodic check-up by ACTH stimulation test is advised. Adrenal insufficiency/hypocortisolism status is the rarest ED (but some reported a prevalence of up to one third of patients). Significantly, many studies did not routinely perform a dynamic test. Atypical EM sites might be found in adrenals, mimicking an incidentaloma. Between 7.5–10% of children with major BTH have DM; screening starts by the age of 10, and ferritin correlated with glycaemia. Larger studies found DM in up to 34%of cases. Many studies do not take into consideration IGF, IGT, or do not routinely include OGTT. Glucose anomalies are time dependent. Emerging new markers represent promising alternatives, such as insulin secretion-sensitivity index-2. The pitfalls of glucose profile interpretation include the levels of HbA1c and the particular risk of gestational DM. Thalassemia bone disease (TBD) is related to hypoGn-related osteoporosis, renal function anomalies, DM, GHD, malnutrition, chronic hypoxia-induced calcium malabsorption, and transplant-associated protocols. Low BMD was identified in both paediatric and adult population; the prevalence of osteoporosis/TBD in major BTH patients varies; the highest rate is 40–72% depending on age, studied parameters, DXA evaluation and corrections, and screening thoracic–lumbar spine X-ray. Lower TBS and abnormal dynamics of bone turnover markers are reported. The largest cohorts on transfusion-dependent BTH identified the prevalence of hypoGn to be between 44.5% and 82%. Ferritin positively correlates with pubertal delay, and negatively with pituitary volume. Some authors appreciate hypoGn as the most frequent ED below the age of 15. Long-term untreated hypoGn induces a high cardiovascular risk and increased FR. Hormonal replacement therapy is necessary in addition to specific BTH therapy. Infertility underlines TED-related hormonal elements (primary and secondary hypoGn) and IO-induced gonadal toxicity. Males with BTH are at risk of infertility due to germ cell loss. IO induces an excessive amount of free radicals which impair the quality of sperm, iron being a local catalyser of ROS. Adequate chelation might improve fertility issues. Due to the advances in current therapies, the reproductive health of females with major BTH is improving; a low level of statistical significance reflects the pregnancy status in major BTH (limited data on spontaneous pregnancies and growing evidence of the induction of ovulation/assisted reproductive techniques). Pregnancy outcome also depends on TED approach, including factors such as DM control, adequate replacement of hypoT and hypoPT, and vitamin D supplementation for bone health. Asymptomatic TED elements such as subclinical hypothyroidism or IFG/IGT might become overt during pregnancy. Endocrine glands are particularly sensitive to iron deposits, hence TED includes a complicated puzzle of EDs which massively impacts on the overall picture, including the quality of life in major BTH. The BTH prognostic has registered progress in the last decades due to modern therapy, but the medical and social burden remains elevated. Genetic counselling represents a major step in approaching TH individuals, including as part of the pre-conception assessment. A multidisciplinary surveillance team is mandatory.