Hormonal dysregulation and bones in thalassaemia--an overview.
Bone disease (BDT) represents a prominent cause of morbidity in patients of both sexes with thalassaemia major (TM). The exact pathogenesis of BDT in TM is multifactorial, still unclear and complicated. Peak bone mass is achieved shortly after completion of puberty and normally remains stable until the third decade of life. After the age of 30 years, age related bone loss begins. Growth hormone (GH) and sex steroids have a crucial role in bone remodelling and therefore are important in helping to establish and maintain peak bone mass for both sexes. The anabolic effects of GH and IGF-1 in bone are important not only for the acquisition of bone mass during adolescence but also for the maintenance of skeletal architecture during adult life. GH deficiency is not a rare finding in adult patients with TM, thus contributing to the development of BDT. Furthermore, patients with TM are often hypogonadal, and therefore the lack of sex steroids in critical periods, such as puberty, contributes to the failure to achieve optimal peak bone mass and to maintain bone mass later in life. Sex steroids probably act by increasing the expression of RANKL by osteoblastic cells, and alterations in the RANK/RANKL/OPG system in favour of osteoclasts are characteristic in TM, where the ratio of sRANKL/OPG is increased. It is still not clear whether DEXA scan is the gold standard for determination of bone density in thalassaemics and if so, whether the WHO criteria for defining osteopenia and osteoporosis are relevant to patients with TM. The question therefore arises whether other methods should be adopted, since DEXA may often overestimate BDT in these patients. BDT in thalassaemia represents a unique clinical entity with a multifactorial aetiology and of complex mechanisms which need to be clarified. It is essential for us to understand the underlying mechanisms of bone destruction and the bony defect at the ultrastructural level in order to be able to design not only preventive strategies but also therapeutic measures.
Skordis
Nicos
N
Paediatric Endocrine Unit, Department of Paediatrics, Makarios Hospital, Nicosia, Cyprus. nskordis@cytanet.com.cy
Efstathiou
Elisavet
E
Kyriakou
Andreas
A
Toumba
Meropi
M