Growth hormone response following growth hormone releasing hormone injection in thalassemia major: influence of pubertal development

Osteoporosis syndrome in thalassaemia major: an overview

Osteoporosis in thalassaemia major (TM) represents a prominent cause of morbidity. The mechanism of pathogenesis of bone disease (BD) in TM is multifactorial and complicated. Peak bone mass is achieved shortly after completion of puberty and normally remains stable until the third decade of life when age-related bone mass begins. Growth hormone (GH) and sex steroids play a crucial role in bone remodeling and in the maintenance of skeletal architecture during adult life. GH and insulin growth factors (IGFs) have anabolic effect in bone formation. Sex steroids act probably by increasing the expression of RANKL by osteoblastic cells and alterations in the RANK/RANKL/OPG system in favor of osteoclasts. Impaired GH secretion and lack of sex steroids in thalassemic patients due to pituitary damage, contribute to failure of achieving optimal peak bone mass. Other endocrine complications such as hypoparathyroidism and vitamin D deficiency have also a detrimental role on bones in TM. It is still questionable whether the international criteria for defining osteopenia and osteoporosis are relevant to patients with TM; also a question arises for the diagnostic methods such as DEXA scan and management of osteoporosis with known treatment protocols, in the thalassaemic patient.

Growth and endocrine function in thalassemia major in childhood and adolescence

BACKGROUND

Thalassemia major is an inherited hemoglobin disorder characterized by chronic anemia and iron overload due to transfusion therapy and gastrointestinal absorption. Iron overload causes most of the associated mortality and morbidity and frequently involves the endocrine glands.

AIM

To review the most pertinent literature on the topic.

METHODS

One hundred and twenty-three papers were evaluated.

RESULTS

Disproportionate short stature is frequent and becomes more evident at puberty because of the lack of growth spurt. Later on, partial height recovery may occur. Long-term treatment with recombinant human GH seems ineffective to improve final height. Pubertal development is characterized by a clinical spectrum ranging from hypogonadism to a simple delay in starting and developing of puberty. Hormonal replacement is mandatory in cases of absent or arrested puberty. Pancreatic beta-cells function may be impaired during adolescence or later on. Its impairment ranges from hyperinsulinemia, secondary to insulin resistance, with normal glucose tolerance to beta-cells failure with insulin-dependent diabetes mellitus. Primary hypothyroidism may affect thalassemic patients from the second decade of life. The thyroid dysfunction may be reversible (if an intensive chelation therapy regimen is started in the precocious phase), stationary, or slowly progressive. Central hypothyroidism is less common and autoimmune thyroiditis absent.

CONCLUSION

Despite the improvement of the treatment, the involvement of the endocrine system still burdens the life of these patients. Further therapeutic improvement would reasonably reduce morbidity and, hopefully, mortality of thalassemic patients and make the endocrine disorders easier to treat.

Thalassaemia and aberrations of growth and puberty

Endocrine dysfunction in Thalassaemia major (TM) is a common and disturbing complication, which requires prompt recognition and treatment. The contribution of the underlying molecular defect in TM to the development of endocrinopathies is significant because the patients with the more severe genetic defects have a greater rate of iron loading through higher red cell consumption. TM patients frequently present delay of growth and puberty with reduction of final height. The pathogenesis of growth failure is multifactorial and is mainly due to chronic anemia and hypoxia, chronic liver disease, zinc and folic acid deficiency, iron overload, intensive use of chelating agents, emotional factors, and endocrinopathies (hypogonadism, delayed puberty, hypothyroidism) and GH-IGF-1 axis dysregulation. Although appropriate iron chelation therapy can improve growth and development, TM children and adolescents treated intensively with desferrioxamine remain short as well, showing body disproportion between the upper and lower body segment. Body disproportion is independent of pubertal or prepubertal period of greater height gain. Treatment with recombinant GH (rhGH) is recommended when GH deficiency is established, and even so, the therapeutic response is often non satisfactory. Growth acceleration is mostly promoted with sex steroids in children with associated pubertal delay. Sexual complications in TM, which include Delayed Puberty, Arrested Puberty and Hypogonadism, present the commonest endocrine complication. Iron deposition on gonadotroph cells of the pituitary leads to disruption of gonadotrophin production which is proven by the poor response of FSH and LH to GnRH stimulation. In the majority of patients gonadal function is normal as most women with Amenorrhea are capable of achieving pregnancy with hormonal treatment and similarly men with azoospermia become fathers. Secondary Hypogonadism appears later in life, and is manifested in women as Secondary Amenorrhea and in men as decline in sexual drive and azzoospermia. The damage to the hypothalamus and pituitary is progressive, even when intensive chelating therapy is given and the appearance of Hypogonadism in both sexes is often unavoidable. Close follow up and proper management is crucial for every patient with TM. Early recognition of growth disturbance and prevention of hypogonadism by early and judicious chelation therapy is mandatory for the improvement of their quality of life. Patients with TM can now live a better life due to modern advances in their medical care and our better understanding in the pathogenesis, manifestation and prevention of endocrine complications.

Growth of children with beta-thalassemia major

Hypertransfusion and regular chelation therapy have allowed improved survival in patients with thalassemia major (TM). Despite medical advances, growth failure and hypogonadism remain significant clinical problems in these patients in adolescence. Disproportionate truncal shortening which is common especially among adolescents with thalassemia, is due to platyspondyly resulting from a combination of factors like hemosiderosis, desferrioxamine toxicity or deficiency of trace elements. Although growth hormone (GH) deficiency and GH neurosecretory dysfunction have been described in TM patients, most short TM patients have normal GH reserve. The low serum IGF-1 and IGFBP-3 concentrations in TM patients despite having normal GH reserve and serum GH binding protein levels suggest that a state of secondary GH insensitivity exists. The pubertal growth spurt may be impaired in TM patients going through spontaneous or induced puberty and may have a negative effect on final adult height. GH therapy in dosages ranging from 0.5-1.0 IU/kg/wk has resulted in a significant improvement in growth velocity in short TM children without any adverse effects on skeletal maturation, blood pressure, glucose tolerance and serum lipids. There is limited evidence that GH treatment can result in an improved final adult height in short TM children. Careful and regular clinical and biochemical monitoring should be preformed on these patients while they are treated with GH.

Final height of thalassemic patients who underwent bone marrow transplantation during childhood

We evaluated the final height achieved by 47 patients who had bone marrow transplantation (BMT) for thalassemia major. Subjects were separated into two groups: patients who received BMT before 7 years of age and patients who received BMT after 7 years of age. Parental height and genetic target height (TH) were calculated. Our data indicated a strict correlation between age at time of transplant and final adult height. The patients whose age at transplant was <7 years had a less impaired growth rate than did patients who were >7 years. Moreover, greatest loss in height was observed in subjects who had higher serum levels of transaminase and ferritin and these biochemical parameters were strictly correlated to the final adult height. Mean final adult height, however, did not differ from the genetic target height in subjects who received BMT before 7 years of age and the final height SDS corrected for TH surpasses even the TH. In contrast, the subjects who received BMT after 7 years of age, failed to achieve their full genetic potential. In conclusion, short stature is present in a significant percentage of transplanted thalassemic children. The data in this study indicate a close effect of the age at time of transplant on subsequent growth rate, but the growth impairment in these subjects remain multifactorial.

Growth, puberty and endocrine function in beta-thalassaemia major

Although delay in onset of puberty is a common cause of growth failure in adolescent thalassaemic patients, growth retardation could also be due to iron overload, the toxic effects of desferrioxamine, or the development of other endocrinopathies such as GH insufficiency or primary hypothyroidism. Abnormal body proportions with truncal shortening are commonly seen and could be due to the disease itself, iron toxicity, delay in puberty or the toxic effects of desferrioxamine. The absence of a pubertal growth spurt during spontaneous or induced puberty is detrimental to the achievement of a normal final adult height. Low serum IGF-I and normal GH reserve in short thalassaemic children imply that a state of relative GH resistance exists. The rise in IGF-I and improvement in growth with GH therapy suggest that this GH resistance is only partial. Although the results of short-term GH therapy are encouraging, the impact of treatment on final height of non-GH deficient short thalassaemic children remains uncertain. Multiple endocrinopathies, including hypogonadism, hypothyroidism and diabetes mellitus, occur mainly in older patients who tend to have high serum ferritin levels. Prognosis for survival is greatly improved if the serum ferritin is kept below 2000 micrograms/l by regular chelation. Chelation therapy initiated early before the accumulation of a significant iron burden or dosages of desferrioxamine in excess of 50 mg/kg/day should be avoided. Serum ferritin should be checked regularly and the "toxicity index" should be used to monitor chelation therapy. In cases of delayed puberty, sexual development should be induced at an appropriate age.