Bridging Regional and Global Perspectives

Serum levels of bioactive IGF1 and physiological markers of ageing in healthy adults

OBJECTIVE

Senescent changes in body composition and muscle strength are accompanied by reduced production of GH and IGF1, but the causal relationship remains elusive. We speculate that serum bioactive IGF1, measured by the IGF1 kinase receptor activation assay, is closer related to human physiological ageing than total IGF1 measured by immunoassay.

DESIGN

We conducted a cross-sectional study in 150 adult males and females, between 20 and 70 years. After an overnight fasting, serum levels of bioactive IGF1, total IGF1 and IGF-binding protein 1 (IGFBP1) and IGFBP3 were assessed. Furthermore, body composition and muscle strength was measured.

RESULTS

Total IGF1 levels were higher in females (P=0.048). Bioactive IGF1 were identical in males and females (P=0.31), decreasing with age. Total IGF1 tended to decrease more with age compared with bioactive IGF1 (-1.48 vs -0.89 percent/year, P=0.052). Total body fat (TBF) was lower and BMI was higher in males (P<0.001 and P=0.005), and both increased with age. Knee extension and elbow flexion force were higher in males (P=0.001 and P=0.001), but decreased with age in both genders.  Total but not bioactive IGF1 was positively correlated to TBF, knee extension and muscle function in males. In multiple linear regression, only age predicted total IGF1, whereas age and IGFBP1 predicted bioactive IGF1.

CONCLUSIONS

Bioactive IGF1 tends to decrease to a lesser extent than total IGF1 with age and was not correlated with measures of body composition or muscle strength. Therefore, levels of circulating bioactive IGF1 does not appear to be a better biomarker of physiological ageing than total IGF1.

The MPS I registry: design, methodology, and early findings of a global disease registry for monitoring patients with Mucopolysaccharidosis Type I

A global, observational disease registry has been established to characterize the course of disease and track clinical outcomes in patients with Mucopolysaccharidosis Type I (MPS I), a rare and treatable lysosomal storage disorder. This report outlines procedures for data collection and presents the recommended minimum schedule of assessments that comprise the disease-specific clinical and laboratory parameters that are tracked in the database. Aggregate data are summarized for the first 302 patients enrolled, representing entries from 24 countries. The median current age of the patients is 9.0 years (range: 0.4-64.8). Syndrome diagnoses include 47% Hurler (severe form), 25% Hurler-Scheie (attenuated form with an intermediate phenotype), 13% Scheie (most attenuated form), and 15% unknown. Younger ages at symptom onset and disease diagnosis are associated with the severe Hurler syndrome, but there is overlap among syndromes. Diagnosis was delayed by years to decades in several patients with Hurler-Scheie and Scheie syndromes. Patients with symptom onset before age 5 are more likely to have a gibbus, cognitive impairment, and pneumonia, whereas patients with symptom onset above age 5 are more likely to have carpal tunnel syndrome, myelopathy, and glaucoma. Cardiac valve abnormalities, joint contractures, corneal clouding, and hernia are reported by over 70% of patients regardless of the age of symptom onset. Approximately 80% of the patients have received enzyme replacement therapy, hematopoietic stem cell transplantation, or both. Overall, the MPS I Registry database contains a broad sample of the global patient population, providing a potentially useful tool for expanding knowledge of MPS I and facilitating evidence-based decisions about the optimal means of monitoring and treating affected individuals.

Cardiovascular disease and risk factors: the role of growth hormone

Clinical studies in patients with acromegaly have shown that growth hormone (GH) exerts both short- and long-term effects on the structure and function of the heart. Moreover, chronic growth hormone deficiency (GHD) has been associated with impaired cardiac performance, low heart rate and impaired left ventricular systolic function. Exercise capacity in patients with GHD is significantly reduced and in some severely affected individuals, dilated cardiomyopathy and heart failure has been reported. GHD has also been associated with a number of risk factors for cardiovascular disease. Altered lipoprotein metabolism and elevated fibrinogen and plasminogen activator inhibitor-1 activity are associated with GHD, and the risk of hypertension is increased in GH-deficient men. Subcutaneous and intra-abdominal fat mass have also been found to be abnormally high in these patients. These effects may contribute to an increased risk of death from cardiovascular disease. GH is therefore an important factor in the development and function of the cardiovascular system. In this paper, the effects of GH on the physiological mechanisms of the cardiovascular system are discussed, including the effect of GHD on cardiovascular disease risk. We will also discuss the effects of long-term GH replacement therapy in this patient population.

Advances in Growth Hormone Therapy: A New Registry Tool

Growth hormone (GH) deficiency is a rare condition, and physicians may lack clinical experience of its treatment. Despite evidence for the efficacy and tolerability of GH therapy, a substantial proportion of patients remain untreated. Registries and other large-scale databases are an important tool for expanding the evidence base for GH treatment. Since the mid-1980s, registries have provided data on important aspects of the safety and efficacy of GH treatment. Registries have also allowed pooling of data from patients with rare conditions that could otherwise not be recruited in sufficient numbers for clinical trials. Importantly for patients and their relatives, use of registry data has allowed the development of prediction models that indicate the likely outcomes of treatment. MEGHA (Metabolic Endocrinology and Growth Hormone Assessment) is a recently developed, observational database with a number of features not found in existing registries, including its use as a day-to-day clinical management tool, the ability to create individual sub-studies, direct comparison of personal data against the full database, and a particular focus on the transition from childhood to adulthood. This creative registry is a promising instrument for further research into GH-related disorders that will improve GH therapy and thus provide benefits for patients.

Stepping into Adulthood: The Transition Period

The period of growth from late puberty to full adult maturation, termed the transition period, is important for tissue maturation. Peak bone mass, muscle mass and strength are usually attained in this period. However, it is common clinical practice in children with growth hormone deficiency (GHD) to discontinue growth hormone (GH) treatment in adolescence after attainment of final height. Therefore, patients with childhood-onset GHD that continues into adulthood and who do not receive treatment as adults may experience more severe consequences than patients who acquire GHD as an adult. Recent studies indicate that bone and muscle maturation are attenuated if GH treatment is discontinued at final height. Furthermore, these patients will also develop cardiovascular risk factors that are normally associated with GHD in adults. Much debate surrounds when retesting for GHD should be carried out and when GH treatment should be restarted in adolescents; many of these patients will not have severe GHD according to the criteria set for adults. The transition period is an appropriate time to modify GH doses. Finally, registries exist that have recorded clinical treatment experiences for children and adults. Tools that collect and analyse data provide an important opportunity to investigate issues related to transition.