Growth hormone replacement therapy (GHRT) in children and adolescents: skeletal impact

Bone mineral density in survivors of childhood brain tumours

BACKGROUND

Osteopenia has been reported in children surviving acute lymphoblastic leukaemia, apparently as consequence of therapy. Few studies have been published on bone mineral density (BMD) evaluation in children surviving from brain tumours. The endocrine system in these patients is frequently affected as consequence of therapeutic interventions such as cranial irradiation and anti-neoplastic agents: growth hormone deficiency is the most common adverse sequel. The pathogenesis of osteopenia in brain cancer survivors is multi-factorial but still uncertain.

OBJECTIVE

The aim of this study is to examine bone mass in 12 brain cancer survivors and its relationship with their hormonal status.

RESULTS AND DISCUSSION

We observed that most of the patients had a BMD that was lower than normal in both the lumbar column and in the femoral neck. Bone mass loss was higher in the lumbar region rather than in the femoral neck, due to spinal radiation therapy and to the effect of hormonal deficiencies. Particularly hypogonadism, but also multiple hormonal deficiencies, are associated with lower BMD values. Experience in clinical care of these patients suggests the importance of periodic evaluations of BMD, especially in those with secondary hormone deficiencies. Moreover, the periodic assessment of the hypothalamus-pituitary function is essential for an early diagnosis of hormonal insufficiency, primarily hypogonadism, to precociously detect bone mineral loss and to prevent pathological fractures, thus improving the quality of life.

Bone mineral metabolism and its relationship to leptin levels in survivors of childhood leukemia and lymphoma

Leptin has important effects on bone metabolism. Possible relationships between leptin and bone mineral density were evaluated in the survivors of the childhood leukemia and lymphoma. Twenty patients were included the study. Anthropometric parameters, growth hormone response to provocative test, serum calcium, phosphorus, alkaline phosphates, osteocalcin, leptin levels, urinary calcium and deoxyypyridinoline levels, and bone mineral density were obtained. Anthropometric parameters of patients were not significantly different from those of a control group. Growth hormone provocative test was abnormal in 3 patients who received cranial radiotherapy. The osteocalcin levels and bone mineral density of patients were significantly lower than in the control group (p=.001, p=.02). Nine patients were in the osteopenic and 7 were in the osteoporotic range. The leptin levels of patients were significantly lower (p=.01) than in the control group. Bone mineral density (BMD) was significantly correlated with leptin level, age, body mass index, and Tanner stage in simple correlation analysis. However, in multivariate analysis only age was significant (p<.000, r: .752). Markers of bone metabolism, BMD, and leptin levels were not related with the growth hormone status of patients and did not present a correlation with the cumulative doses of drugs. There are a few studies evaluating the relationship between BMD and leptin levels in childhood cancer. Although this study did not find any correlation between the leptin level and BMD, detailed studies of larger numbers of patients are necessary to evaluate causes of decreased leptin level and the possible role of leptin on osteopenia observed in survivors of childhood cancer.

An effective case of growth hormone treatment on cartilage-hair hypoplasia

Cartilage-hair hypoplasia (CHH) is an autosomal recessive metaphyseal chondrodysplasia characterized by severe short-limb short stature and hypoplastic hair. The responsible gene for CHH has been identified to be ribonuclease of mitochondrial RNA-processing (RMRP) gene. We examined RMRP genes of a 3-year-old Japanese CHH boy and his family and revealed a novel mutation: 20 bp duplication (TACTCTGTGAAGCTGAGGAC), in promoter region of maternal allele, at nucleotide -3 and a reported 218A>G point mutation in transcribed region of paternal allele. No treatment for CHH has been established so far. Growth hormone (GH) action has its effect on linear growth and on bone remodeling and homeostasis. Recently, GH has been used to improve severe short stature caused by not only GH deficiency (GHD) but also some skeletal dysplasias including achondroplasia. To improve severe short stature, we treated the patient with 0.175 mg kg-1 week-1 of GH for 7 years. His height was improved from -4.2 SD to -3.0 SD by 1 year of GH treatment. Following treatment had given positive effects continuously on his height to -2.6 SD by 3.1 years GH medication. Then, when he was 6 years old, surgical lengthening was performed and his height reached to -2.0 SD. After the surgery, we continued GH treatment. Additional GH treatment of 3.6 more years had kept his height to -2.0 SD. However, when he was 8 years old, because there was an interruption of GH treatment, the velocity of his height was obviously decreased comparing before and during the interruption, which was calculated 3.4 and 2.2 cm/year, respectively, and the SD score was decreased to -2.1 SD. This result of total 7 years of GH treatment suggested that GH treatment significantly improved his disturbed bone growth and had also positive efficacy to keep growth rate. This result implies the connection between GH signal and RMRP gene. Additionally, GH may be considered to be an efficient treatment for CHH.

Long-Term Challenges in Growth Hormone Treatment

Growth hormone deficiency (GHD) is defined biochemically as a response to hypoglycaemia with a peak GH concentration of less than 5 microg/l. The 'GHD syndrome' is a range of psychological and physical symptoms that are associated with GHD, which include increased central adiposity, decreased bone mineral density, abnormal lipid profiles, decreased cardiovascular performance, reduced lean body mass (LBM), social isolation, depressed mood and increased anxiety. Importantly, the combination of physical and psychological problems can often result in a reduced quality of life. A number of trials have shown that GH replacement therapy can lead to a substantial improvement in GHD associated symptoms. Following up to 12 months of treatment with GH, LBM increased, left ventricular systolic function improved and the mean volume of adipose tissue fell. After only 4 months of treatment, a rise in exercise capacity was recorded, and after 2 years' treatment, isokinetic and isometric muscle strength had normalized in proximal muscle groups. Feelings of well-being and vitality also improved significantly. However, studies on the effects of treatment on insulin sensitivity in GH-deficient patients have had conflicting results. In this paper, we will discuss the long-term consequences of GHD and the effects of GH replacement therapy.