Pediatric endocrinology reviews : PER最新文献

The European Marketing Authorization for recombinant human growth hormone (rhGH) in children with Prader-Willi syndrome was the first indication for metabolic and body composition effects in children. In the US it is indicated for short stature associated with PWS. Recombinant hGH is the first treatment for the PWS population and radically changed the care of these children by facilitating access to physicians who prescribe rhGH, mainly paediatric endocrinologists, and manage the organization of multidisciplinary care. Recombinant hGH treatment improved linear growth, body composition, and socialization not only in children but also in young adults. The pathophysiology of combined hormonal deficiencies including GH is starting to be unravelled. We now have to focus on co-morbidities that are not modified by rhGH treatment, such as feeding disorders and behaviour problems, to truly change the life of patients. The transition of care from adolescents to young adults also remains a challenge.

Human growth hormone (hGH), which had been in use since 1958, was supplanted by recombinant human growth hormone (rhGH) in 1985 for those with growth hormone deficiency (GHD). Adherence to daily subcutaneous growth hormone is challenging for patients. Thus, several companies have pursued the creation of long acting rhGH. These agents can be divided broadly into depot formulations, PEGylated formulations, pro-drug formulations, non-covalent albumin binding GH and GH fusion proteins. Nutropin Depot is the only long acting rhGH ever approved by the U.S. Food and Drug Administration, and it was removed from the market in 2004. Of the approximately seventeen candidate drugs, only a handful remain under active clinical investigation or are commercially available.

Between 1958 and today, advances in research and the clinical management of short stature with GH have occurred. Initially, limited supply of pituitary-derived hGH led to strict criteria for diagnosing GH deficiency and tightly controlled treatment protocols. With the advent of biosynthetic GH, the supply has increased, the number of indications for treatment has grown, and the focus of intervention changed from hormone replacement to treatment of short stature. Improved psychosocial adaptation is an underlying, albeit largely unspoken and inadequately researched, target of treatment. Complicating the ability to make a definitive statement on the effects of rhGH on psychosocial adaptation is the rigor of the psychological outcomes literature. A high risk of bias present in the majority of rhGH treatment studies on psychological outcomes substantially weakens confidence in their results. Studies that convincingly demonstrate, through rigorous research design and methodology, that the benefits of rhGH exceed the risks and burdens are needed.

The GH/IGF axis plays an important role in the control of pre and postnatal growth. At least 48 monogenic defects have been described affecting the production, secretion, and action of GH and IGFs. Molecular defects of the GH/IGF axis resulting in short stature were arbitrarily classified into 4 groups: 1. Combined pituitary hormone deficiency (CPHD) (a. syndromic CPHD and b. non-syndromic CPHD), 2. Isolated GH deficiency (IGHD), 3. GH insensitivity, and 4. IGF-I insensitivity. Genetic diagnosis is obtained in about 30-40% of children with growth retardation, severe IGHD, CPHD, apparent GH or IGF-I insensitivity, and small for gestational age. Increased accessibility to next generation sequencing (NGS) techniques resulted in a significant number of likely pathogenic variants in genes previously associated with short stature as well as in completely novel genes. Functional in vitro assays and in vivo animal models are required to determine the real contribution of these findings.

Noonan syndrome (NS) is a genetic disorder, which can present clinically with a variable phenotype. Proportional post natal short stature is a common manifestation of NS, with the majority of affected patients having an adult height below the third percentile. Some investigators have reported minor abnormalities in GH secretion and/or action, suggesting that recombinant growth hormone (rhGH) therapy may be useful for the treatment of their short stature. Our review of the literature regarding rhGH therapy in children with NS indicates that this therapy improves height velocity, but relatively few controlled clinical trials reporting adult height are available. rhGH treatment does not appear to be associated with adverse effects in these patients, but data on the possible development of malignancy during treatment are somewhat limited. Therefore, we believe that there is a need for large controlled clinical trials in patients with this condition, in order to accurately assess the effects of rhGH therapy over adult height.

ISS is the commonest cause of short stature and poor growth and is arbitrarily defined as a height < -2 SDS without an identified cause. ISS consists largely of normal children with the remainder unrecognised conditions, mainly syndromes and genetic (monogenic and polygenic) causes. Growth response to rhGH is widely variable reflecting the heterogeneity of ISS. Further identification of genetic causes of ISS will better characterise treatment response. rhGH during childhood has been shown in RCTs to improve adult height by approximately 4 cm which is less than seen in other treated growth disorders. Factors that influence response include; younger age, longer birth length, lower height compared to mid-parental height, delayed bone age and larger rhGH dose. The evidence that short stature is associated with psychological well-being and quality of life is minimal and that rhGH could improve this is scant. Further research in this area is urgently required.

Determination of serum levels of GH and IGF-I is crucial for the diagnosis and treatment of GH deficiency and disorders related to GH excess such as acromegaly and pituitary gigantism. However, significant discrepancies in measured GH values among the methods were observed around the world. In Japan, the Study Committee for GH and Its Related Factors of The Foundation for Growth Science standardized GH values measured with various commercially available GH assay kits by creating formulas to adjust them to their averages. The committee also established reference values for IGF-I in Japanese subjects at all ages from childhood to adulthood. Internationally, collaborators have been working on the harmonization of GH measurements.

The first patient treated with cadaveric pituitary GH (hGH) was reported in 1958. Subsequently, collection of cadaveric pituitaries started in many countries and several centers extracted the hormone using one of two methods: a. Acetone preservation and extraction with hot glacial acetic acid (Rabin method) b. Collection in distilled water, freezing and extraction on columns yielding several pituitary hormones including hGH (Wilhelmi method). The purified extracts of hGH were found to have metabolic and growth stimulating activity but the limited amounts permitted the treatment only of children with GH deficiency (GHD). The purified hormone also permitted the development of specific radioimmunoassays enabling the study of the physiological and pharmacological actions of GH. In 1985 a number of patients treated years before with Wilhelmi hGH were diagnosed with Creutzfeld-Jacob-Disease (CJD). This led to the arrest of hGH production and the use of the then recently developed biosynthetic recombinant hGH.

During the phase of using hGH extracted from pituitaries (pit hGH) - 1958-1985 - fundamental experience related to the diagnosis and treatment was accumulated. However, since recombinant hGH (rhGH) had become available diagnosis and treatment of GHD were conducted world-wide in a more standardized way. Treatment with rhGH was also accompanied by documentations in large international pharmaco-epidemiological surveys, which provided new insight. Despite of this development the treatment of children and adolescents with GHD raises still issues related to the most effective and efficacious as well as safe use of rhGH. This brief review attempts to discuss a few aspects related to these topics as they have developed during the rhGH era.