Growth Velocity, Final Height and Bone Mineral Metabolism of Short Children Treated Long Term with Growth Hormone

Roberto      Lanes

doi:10.2174/1389201003378997

Abstract

Since human recombinant growth hormone (GH) became available a large number of short GH deficient and GH-sufficient children have been treated with growth hormone. Growth hormone deficient patients have been followed to final height and several studies have shown that even when treated with GH from very early on in life they tend to end up shorter than their target height. There is, however, a clear increase in their growth velocities particularly during the first 4-5 years of GH therapy so that patients end up with a height-SD score of aproximately -0.8. Recent studies have demonstrated decreased bone mineral densities (BMD) in children with growth hormone deficiency, both by areal and volumetric analysis. Therapy with growth hormone clearly increases their BMD with an increase in bone formation markers, as will be reviewed in detail. Growth hormone therapy of non-growth hormone deficient short children has increased their growth velocity short term, particularly in girls with Turner ’ s syndrome and in children with chronic renal insuficiency. Recent final height data by Rosenfeld et al. and by Swedish and Dutch groups have demonstrated a gain of 8-12 cm in girls with Turners syndrome treated with GH or with a combination of GH and oxandrolone. Neely et al. and we have demonstrated that growth hormone treated prepubertal age girls and adolescents with Turners syndrome have normal BMD and Shaw et al. has suggested that they have normal BMD despite GH or estrogen therapy. However, we found the BMD of a group of previously GH treated young women with Turners syndrome on estrogen replacement to be decreased compared to both age and gender matched controls and to controls of the same weight and pubertal status. Growth hormone therapy increases the growth velocity and the final height of children with chronic renal insuficiency, particularly in prepubertal children treated with GH before dialysis. We have demonstrated how the BMD of these patients, which at baseline is low when compared to heal thy age matched controls, but normal when compared to height and bone age matched controls, increases with growth hormone treatment significantly, moreso than in untreated uremic controls or in untreated healthy controls paired for height and bone age. Short, slowly growing, non growth hormone deficient patients (idiopathic short stature) have been treated for prolonged periods of time with GH. We and others have demonstrated a clear increase in their growth velocity short term, but improvement of their final height remains unclear and controversial. After 4-8 years of GH treatment, Hintz et al. have found a 5-6 cm increase in final height compared to the predicted adult height before beginning therapy, but most patients did not reach their target heights. Other studies, however, have found no improvement in final height and Kawai et al. even suggests that GH therapy diminishes the final height of treated children due to an earlier puberty and a shorter pubertal growth spurt. We, have found decreased BMD in children with idiopathic short stature when compared to controls of their same height and bone age with a significant increase in BMD following 12 months of GH and with an increase in bone turnover as measured by bone formation and resorption ma rkers. Recent short term studies in patients with hypophosphatemic rickets and osteogenesis imperfecta treated with rhGH have also yielded similar results which will be specified in the review. Some 10-20percent of children born with intrauterine growth retardation (IUGR) end up short and we had already demonstrated 20 years ago how 2 years of GH therapy were capable of increasing their growth velocities significantly with an improvement of their height-SD scores. Recent studies mainly from Europe have corroborated this data long term, so that IUGR children have been shown by de Zegher et al. to increase their growth velocities and their height for age after 6 years of treatment, entering into the low normal centiles of their growth curves for age. Long term studies of these children to final height will be necessary to determine the usefulness and safety of this form of therapy.

Keywords: Bone Mineral Metabolism, Growth Hormone Deficiency, Turners syndrome, Idiopathic short stature, UREMIA

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