Hormone research最新文献

Background: Several therapeutic trials have been conducted over the past decade to evaluate the role of exogenous growth hormone (GH) as a means of correcting the growth deficiency seen in children with juvenile idiopathic arthritis (JIA). Early studies showed the benefit of GH treatment with respect to final height in patients with JIA. Of 13 patients receiving GH, 84% (11 patients) achieved a final height within their target range compared with only 22% (4 of 18 patients) of untreated patients. There are, however, factors that may limit the statural gains achieved with GH therapy including severe inflammation, severe statural deficiency at GH therapy initiation, long disease duration and delayed puberty. Data on the efficacy of GH replacement therapy in children with JIA and factors that influence the statural growth response will be reviewed.

Conclusions: Results from therapeutic trials show that treatment with GH can decrease the statural deficit that occurs during the active phase of JIA, producing an adult height that is close to the genetically determined target height.

Background: In patients with juvenile idiopathic arthritis (JIA), growth impairment and altered body composition, including disturbed skeletal development, are well-known long-term complications. Data on longitudinal growth in patients with systemic and polyarticular JIA reveal growth impairment in the active phases of the disease. With reduction in disease activity and lower glucocorticoid (GC) doses, some patients experience 'catch-up' growth; however, many have only a slight improvement in height standard deviation during puberty or after cessation of GC treatment. The consequence is a final height below the 3rd percentile and below the genetic height potential. Although few studies have specifically addressed body composition in children with JIA, studies on the development of bone mass have described notable deficits in both GC-treated and GC-naïve children. In recent years, the deficits in bone mass have been related, in part, to the deficits in muscle mass, which are prevalent in these patients.

Conclusions: The major goal for physicians caring for patients with JIA is optimal disease control while maintaining normal growth. Early recognition of patients who develop prolonged growth disturbances and altered body composition is important as these abnormalities contribute to long-term morbidity and need to be addressed both diagnostically and therapeutically when treating children with JIA.

Background: Growth disorders are commonly observed in children with chronic inflammatory disease. It is likely that these disorders are mediated by a combination of factors, including the disease process and its treatment (with drugs such as glucocorticoids [GCs]). These factors affect the growth hormone-insulin-like growth factor I (IGF-I) axis, which is crucial for promoting linear growth at the level of the growth plate. Recent advances in our knowledge of the effects of GCs and proinflammatory cytokines on the growth plate have led to an improved understanding of the biological rationale for the use of growth-promoting therapy in children with chronic inflammatory disease and concurrent growth retardation.

Conclusions: Both GCs and proinflammatory cytokines can adversely affect a number of components of growth plate chondrogenesis, and these effects can be ameliorated by raising local IGF-I exposure. However, this intervention does not lead to complete normalization of the growth plate. In children with chronic inflammation, the cornerstone of improving growth remains the judicious use of GCs while ensuring effective control of the disease process.

Background: Chronic administration of glucocorticosteroids (GCs) can have significant catabolic effects in vivo in a host of metabolic systems, including amino acid metabolism, skeletal muscle, bone and linear growth. GCs inhibit protein synthesis and increase protein breakdown at the skeletal muscle and whole-body level and impair growth hormone (GH) secretion and action. Conversely, GH and insulin-like growth factor I (IGF-I) are potent protein-anabolic and growth-promoting agents in vitro and in vivo. This review summarizes both the catabolic effects of GCs and the anabolic and metabolic effects of GH and IGF-I.

Conclusions: Both GH and IGF-I may decrease the catabolic effects of chronic steroid use in humans, particularly by enhancing lean body mass accrual and, in children, by increasing linear growth.

Pituitary adenomas occur in a familial setting in about 5% of all cases, and over half of these are due to multiple endocrine neoplasia type 1 (MEN1) and Carney's complex (CNC). Non-MEN1/CNC familial pituitary tumours of all tumour phenotypes, known as familial isolated pituitary adenomas (FIPA), were first described in the late 1990s. Clinical features of FIPA differ from those of sporadic pituitary adenomas, as patients with FIPA have a younger age at diagnosis and larger tumours. About 15% of patients with FIPA have mutations in the aryl hydrocarbon receptor-interacting protein gene (AIP), which indicates that FIPA may have a diverse genetic pathophysiology. This article describes the clinical features of FIPA, the tumour pathologies found in this setting and the genetic/molecular data that have recently been reported in FIPA.

Although several genes and signalling pathways have been identified as important effectors in the development of pituitary tumours, our understanding of pituitary tumorigenesis remains incomplete and is the focus of much current research. Use of the mRNA differential display technique in prolactinomas from D2-receptor knockout mice and in stable GH3 cell line clones with enhanced tumorigenicity in vivo has led to the identification of two genes that are involved in the pathogenic process--BMP-4 and RSUME. Bone morphogenetic protein-4 (BMP-4) has been found to have a crucial role in prolactinoma development and also in signalling crosstalk with oestrogens. In contrast, BMP-4 has an inhibitory role in corticotrophinomas. RSUME (RWD-containing sumoylation enhancer) was identified from a transformed lactosomatotrophic cell line that had increased tumorigenic and angiogenic potential. Expression of RSUME was induced under hypoxic conditions and it has a potential role during vascularization. The differential expression and action of BMP-4 in prolactinomas and corticotrophinomas highlights the importance of studying a gene with contrasting actions in two cell lineages of the same organ in order to understand the pituitary transformation process. Both BMP-4 and RSUME may be interesting targets for inhibiting steps involved in pituitary tumorigenesis.

The genesis of pituitary tumours is still under debate. Although these neoplasias are monoclonal in origin, mutations of GNAS1, the gene encoding the alpha subunit of the stimulatory G-protein, Gs, are the only mutational changes unequivocally associated with growth hormone (GH)-secreting adenomas. However, despite the growth advantage that this oncogene has been demonstrated to confer in vitro, patients carrying this mutation have a similar clinical and biochemical phenotype to those who do not carry it. This discrepancy is due to the occurrence of events able to counteract the biological effect of the mutation. Consistent with a potential role of the cyclic adenosine monophosphate pathway in the proliferation of somatotrophs, germline mutations of the gene encoding the type 1alpha regulatory subunit of protein kinase A (PRKAR1A) have been found in patients with the Carney complex, a syndrome including GH-secreting adenomas, whereas alterations in the expression levels of this subunit are frequently observed in sporadic adenomas.

The hallmarks of epigenetics--the memory of defining earlier developmental events and the distinction of active and inactive genes--are exemplified by imprinted genes. In this article, I shall consider the imprinted Gnas locus in some detail. Gnas encodes the stimulatory G-protein subunit, Gsalpha, an essential intermediate between receptor coupling and cyclic adenosine monophosphate generation. It provides an excellent illustration of the pleiotropic effects of imprinted genes, particularly on skeletal growth and metabolism, and is a powerful example of the conflicting effects of imprinted genes with opposing patterns of imprinting. I shall describe the effects of Gsalpha deficiency in humans and the knowledge gained from genetic manipulation in the mouse. Finally, given the pervasive effects of imprinted genes, I shall discuss the likelihood that epigenetic deregulation, for example of imprinted genes, could contribute to the developmental programming of chronic adult diseases.