Screening for glucose dysregulation in β-thalassemia major (β-TM): An update of current evidences and personal experience

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.

A prospective guide for clinical implementation of selected OGTT- derived surrogate indices for the evaluation of β- cell function and insulin sensitivity in patients with transfusion-dependent β- thalassaemia

The gold standard for the measurement of insulin secretion is the hyperglycemic clamp and for insulin sensitivity the hyperinsulinemic euglycemic clamp, respectively. A number of surrogate indices, derived from plasma glucose and insulin levels at a fasting state or after oral glucose load, have been proposed to estimate β-cell response, and the ability of β-cells to compensate for changes of insulin sensitivity by modulating insulin secretion (disposition index). Starting from the current recommendations for the annual screening of glucose dysregulation in patients with transfusion dependent β-thalassemia (β-TDT), this article summarizes the most frequently used indirect indices of insulin secretion and resistance derived from the oral glucose tolerance test (OGTT) and discusses the strengths and weaknesses of selected indices and the basic concepts underlying each method for the appropriate evaluation of glucose regulation. Basal indices for β-cell function and insulin sensitivity, albeit simple and cheap, have limited usefulness due to a high coefficient variation and the lack of data about response to glucose load. Therefore, measurement of indices during an OGTT, despite being costly and time-consuming, is suggested since it can detect, even subtle, dynamic changes in insulin secretion and glucose handling. In patients with β-TDT, the indices derived from OGTT may offer an additional factor to evaluate the efficiency of iron chelation therapy and detect patients who may need intensification of iron chelation therapy and/or pharmacological intervention.

Retrospective study on long-term effects of hormone replacement therapy (HRT) and iron chelation therapy on glucose homeostasis and insulin secretion in female ß- thalassemia major (β-TM) patients with acquired hypogonadotropic- hypogonadism (AHH)

BACKGROUND AND AIM

Hypogonadism and abnormalities of glucose homeostasis, resulting from iron-induced pituitary and pancreatic β-cell dysfunction respectively, are the most frequently reported endocrine abnormalities in patients with ß-thalassemia major (β-TM), also identified as transfusion-dependent thalassemia (TDT).

STUDY DESIGN AND PATIENTS

The aim of the present retrospective study was to evaluate the long-term effects of hormone replacement therapy (HRT) on glucose metabolism and insulin secretion/sensitivity during 3-h oral glucose tolerance test (OGTT) in adolescent and young β-TM women with acquired hypogonadototropic -hypogonadism (AHH).Twelve hypogonadal β-TM females with AHH on HRT were followed for 8.26 ± 1.49 years.

RESULTS

At baseline, 10 patients (83.3%) had normal OGTT, 1 patient presented with impaired glucose tolerance (IGT) and 1 patient had an isolated PG level of 165 mg/dL at 1-h during OGTT (H-NGT). At last evaluation, 7 patients (58.4 %) had normal OGTT, while 5 patients (41.6%) had abnormal OGTT. Reduced insulin sensitivity and impaired first-phase insulin secretion were also documented. Three of 4 β-TM patients on treatment with estradiol hemihydrate MX 50 patches plus oral medroxyprogesterone acetate (MPA), associated with a very effective iron chelation therapy, maintained normal glucose tolerance from baseline to last evaluation. Significant adverse events due to HRT or additional endocrine complications were not documented in any cases during the follow-up.

CONCLUSION

Deterioration of glycemia (dysglycemia) occurred in 45.4% (5/11) of thalassemic females on long-term HRT. Additional studies are needed to elucidate the validity of our preliminary observations.

Assessment of glucose homeostasis in young adult female β-thalassemia major patients (β-TM) with acquired hypogonadotropic hypogonadism (AHH) never treated with sex steroids compared to eugonadal β-TM patients with spontaneous menstrual cycles

BACKGROUND

Acquired ypogonadotropic hypogonadism (AHH) is the most prevalent endocrine complication in thalassemia major (TM).

STUDY DESIGN

Considering the detrimental effect of estrogen deficiency on glucose metabolism, the ICET-A Network promoted a retrospective study on the long-term effects of estrogen deficiency on glucose homeostasis in female β-TM patients with HH without hormonal replacement therapy (HRT).

PATIENTS AND METHODS

Seventeen β-TM patients with AHH (4 had arrested puberty; Tanners' breast stage 2-3), never treated with sex steroids, and 11 eugonadal β-TM patients with spontaneous menstrual cycles at the time of referral were studied. A standard 3-h OGTT was performed in the morning, after an overnight fast. Six-point plasma glucose and insulin level determinations, indices of insulin secretion and sensitivity, early-phase insulin insulinogenic index (IGI), HOMA-IR and β-cell function (HOMA-β), oral disposition index (oDI), glucose and insulin areas under the OGTT curves were evaluated.

RESULTS

Abnormal glucose tolerance (AGT) or diabetes was observed in 15 (88.2%) of 17 patients with AHH and 6 (54.5%) of 11 patients with eumenorrhea. The difference between the two groups was statistically significant (P: 0.048). However, the group of eugonadal patients was younger compared to AHH patients (26.5 ± 4.8 years vs. 32.6 ± 6.2 years ; P: 0.010). Advanced age,  severity of iron overload, splenectomy, increased ALT levels and reduced IGF-1 levels were the main clinical and laboratory risk factors for glucose dysregulation observed in β-TM with AHH compared to eugonadal β-TM patients with spontaneous menstrual cycles.

CONCLUSION

These data further support the indication for an annual assessment of OGTT in patients with β-TM. We believe that a registry of subjects with hypogonadism is necessary for a better understanding of the long-term consequences of this condition and  refining treatment options.

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.

Longitudinal study of ICET-A on glucose tolerance, insulin sensitivity and β-cell secretion in eleven β-thalassemia major patients with mild iron overload

BACKGROUND

Iron chelation therapy (ICT) is the gold standard for treating patients with iron overload, though its long-term effects are still under evaluation. According to current recommendations regarding  transfusion-dependent  (TD)  β-thalassemia major (β-TM) patients, their serum ferritin (SF) levels should be maintained below 1,000 ng/mL and ICT should be discontinued when the levels are <500 ng/mL in two successive tests. Alternatively, the dose of chelator could be considerably reduced to maintain a balance between iron input and output of  frequent transfusions.

STUDY DESIGN

Due to the paucity of information on long-term effects of ICT  in β-TM with low SF levels on glucose homeostasis, the International Network of Clinicians for Endocrinopathies in Thalassemia and Adolescence Medicine (ICET-A) promoted a retrospective and an ongoing prospective observational study with the primary aim to address the long-term effects of ICT on glucose tolerance and metabolism (β-cell function and peripheral insulin sensitivity) in adult β-TM patients with persistent SF level below 800 ng/mL.

PATIENTS AND METHODS

11 β-TM patients (mean age: 35.5 ± 5.5 years; SF range: 345-777 ng/mL) with normal glucose tolerance test (OGTT) or abnormal glucose tolerance (AGT) for a median of 5.3(1.1-8.3) years.

RESULTS

Abnormal glucose tolerance (AGT) was observed in 7 patients (63.6%) at first observation and ) persisted in 6 patients (54.5%) at last observation. None of them developed diabetes mellitus. AGT was reversed in two patients. One patient with NGT developed early glucose intolerance (1-h PG ≥155 and 2-h PG <140 mg/dL). Three out of  5 patients with isolated impaired glucose tolerance presented a variation of  ATG. Stabilization of low indices for β-cell function and insulin sensitivity/resistance was observed. One patient developed hypogonadotrophic hypogonadism. Three out of 6 patients with SF below 500 ng/dL had hypercalciuria.

CONCLUSION

Despite low SF level, the burden of endocrine complications remains a challenge in β-TM patients. The ability to keep iron at near "normal" level with acceptable risks of toxicity remains to be established.

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.

The evolution of glucose-insulin homeostasis in children with β-thalassemia major (β -TM): A twenty-year retrospective ICET- A observational analysis from early childhood to young adulthood

BACKGROUND

Thalassemia guidelines recommend oral glucose tolerance test (OGTT), starting from the age of 10 years, or earlier in the presence of iron overload.

OBJECTIVE

The aim of this retrospective study was to review and document the changes of glucose-insulin homeostasis from early childhood to young adulthood in β-thalassemia major (β -TM) patients with impaired fasting glucose (IFG) and normal OGTT.

METHODS

All data of the clinical patients' records of 18 β -TM patients' from September 1983 to September 2021 were included in the study. Annual or biennial OGTT results, for a duration of 15-20 years, were available for all patients.

RESULTS

The main findings are: a) IFG in children with β -TM represents a risk factor for the development of glucose dysregulation (GD) at later age; b) fluctuations of glucose homeostasis during follow-up were observed mainly in β-TM patients with IFG at baseline; and c) the primary defect of GD appears to be a low degree insulin resistance (IR), as estimated by HOMA-IR, followed by an insulin secretion defect.

CONCLUSION

These results are noteworthy as they revealed that firstly, the baseline IFG predicts future development of GD, and secondly, that almost half of patients with IFG at the outset had normal glucose handling 15 years later. Understanding the sequence of abnormalities in the progression from normal glucose homeostasis to GD and identifying the risk factors for the glycometabolic defects in thalassemic patients might help in the formulation of interventions.

Oral glucose tolerance test: Ηow to maximize its diagnostic value in children and adolescents

BACKGROUND

Recently, the validity of the oral glucose tolerance test (OGTT) as a gold-standard test for the diagnosis of glucose dysregulation (GD) has been questioned due to the pre-analytical, analytical, and post-analytical variables which can potentially affect its reproducibility and accuracy.

AIMS

In this short update, the many  variables that affect the reproducibility and accuracy of the OGTT are described and discussed aiming to enhance its diagnostic value  in  clinical practice.

SEARCH STRATEGY

A systematic search was implemented in June 2022, using Scopus, PubMed, Embase and Google Scholar focusing on OGTT relevant  papers published in the last 10 years. Moreover,  the reference lists of these  articles were checked for additional pertinent studies. The research and selection of articles was also supported by the long-term authors' experience in the use of OGTT for the diagnosis of GD in children and adolescents.

CONCLUSION

The complexity of diagnosing GD presupposes that clinicians have specific knowledge and experience to perform rigorous assessment of glucose metabolism. It is worth mentioning that during OGTT, subjects with glucose levels  close to the cut-off values proposed  by WHO (World Health Organization)/ADA (American Diabetes Association) require careful evaluation in order to avoid misclassification and unnecessary interventions. For this reason, ADA recommends a second test to confirm the diagnosis of diabetes.