Evaluation of growth hormone secretion and treatment

Effect of continuous positive airway pressure on insulin growth factor-1 in patients with obstructive sleep apnea: a meta-analysis

OBJECTIVE

Obstructive sleep apnea (OSA) has been recognized as being associated with low level of insulin growth factor-1 (IGF-1). However, the impact of OSA treatment using continuous positive airway pressure (CPAP) on IGF-1 remains controversial. We performed a meta-analysis to determine whether effective CPAP therapy could increase IGF-1 levels.

DESIGN

Two reviewers independently searched PubMed, Cochrane library, Embase and Web of Science before September 2014. Information on characteristics of subjects, study design and pre- and post-CPAP treatment of serum IGF-1 was extracted for analysis. Standardized mean difference (SMD) was used to analyze the summary estimates for CPAP therapy.

RESULTS

Six articles with 168 patients were included in this meta-analysis, including five observational studies and one randomized controlled study. The meta-analysis showed that CPAP was associated with a statistically significant increase in IGF-1 in OSA patients (SMD=-0.436, 95% confidence interval=-0.653 to -0.218, P=0.000).

CONCLUSIONS

This meta-analysis suggested that CPAP therapy was associated with an increase in IGF-1 in patients with OSA. Further large-scale, well-designed interventional investigations are needed to clarify this issue.

The GH/IGF-1 Axis and Heart Failure

The growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis regulates cardiac growth, stimulates myocardial contractility and influences the vascular system. The GH/IGF-1 axis controls intrinsic cardiac contractility by enhancing the intracellular calcium availability and regulating expression of contractile proteins; stimulates cardiac growth, by increasing protein synthesis; modifies systemic vascular resistance, by activating the nitric oxide system and regulating non-endothelial-dependent actions. The relationship between the GH/IGF-1 axis and the cardiovascular system has been extensively demonstrated in numerous experimental studies and confirmed by the cardiac derangements secondary to both GH excess and deficiency. Several years ago, a clinical non-blinded study showed, in seven patients with idiopathic dilated cardiomyopathy and chronic heart failure (CHF), a significant improvement in cardiac function and structure after three months of treatment with recombinant GH plus standard therapy for heart failure. More recent studies, including a small double-blind placebo-controlled study on GH effects on exercise tolerance and cardiopulmonary performance, have shown that GH benefits patients with CHF secondary to both ischemic and idiopathic dilated cardiomyopathy. However, conflicting results emerge from other placebo-controlled trials. These discordant findings may be explained by the degree of CHF-associated GH resistance. In conclusion, we believe that more clinical and experimental studies are necessary to exactly understand the mechanisms that determine the variable sensitivity to GH and its positive effects in the failing heart.

Changes in serum levels of IGF-1 and in growth following adenotonsillectomy in children

OBJECTIVE

Adenotonsillar hypertrophy can cause upper airway obstruction and may be associated with growth delay in children. The objective of this study was to evaluate the long-term effects of adenotonsillectomy on height, weight, and body mass index (BMI) in children with sleep-disordered breathing (SDB).

METHODS

Fifty-two children (mean age 6.2+/-2.3 years) clinically diagnosed with SDB were enrolled. Children were diagnosed and scheduled for adenotonsillectomy (T&A) based on their responses to the validated, 22-item Sleep Related Breathing Disorder (SRDB) scale and a physical examination that showed adenotonsillar hypertrophy. Weight, height, and BMI were evaluated before and 5 years after T&A. Serum levels of insulin-like growth factor-1 (IGF-1) were measured before and 1 month after T&A.

RESULTS

Serum levels of IGF-1 were significantly higher at 1 month after T&A compared to before T&A (p<0.001). Thirty children (58%) returned for follow-up testing 5 years later. Their Z scores (standard deviation scores) for weight, height, and BMI of 30 children were significantly higher 5 years after T&A compared to before T&A (p<0.01).

CONCLUSION

Children with SDB who undergo adenotonsillectomy show significant, long-term increases in weight, height and BMI, as well as a significant increase in serum levels of IGF-1.

Low level of IGF-1 in obesity may be related to obstructive sleep apnea syndrome

The aim of this study was to compare serum insulin-like growth factor (IGF-1) levels in patients with obstructive sleep apnea syndrome (OSAS) with those of nonapneic controls and to determine the risk factors of low IGF-1 levels in patients with OSAS. The study included 39 newly diagnosed moderate-to-severe OSAS patients and 36 nonapneic controls. Overnight polysomnography (PSG) was performed in all patients. The circulating levels of IGF-1 in the OSAS group were significantly lower than those of the control group (p < 0.05). There was a significant negative correlation between IGF-1 and logarithmic transformation (Ln) of the apnea-hypopnea index (AHI), duration of apnea-hypopnea, arousal index, average desaturation, and oxygen desaturation index (ODI). The result of stepwise regression analyses showed that OSAS (p = 0.001) was a risk factor for a low IGF-1 level, independent of age, gender, and body mass index (BMI). Our findings demonstrated that there was a significant negative correlation between IGF-1 and Ln AHI and that OSAS reduced the circulating levels of IGF-1.

Growth and biochemical markers of growth in children with snoring and obstructive sleep apnea

OBJECTIVE

The pathophysiological mechanisms of growth impairment frequently associated with the obstructive sleep apnea syndrome (OSAS) in children are poorly defined. The main objective of this study was to evaluate whether nighttime upper airway obstruction attributable to adenotonsillar hypertrophy and subsequent surgical treatment affect the circulating concentrations of insulin-like growth factor-I (IGF-I) and IGF-binding protein 3 (IGFBP-3) along with other growth parameters in children.

PATIENTS AND METHODS

We initially studied 70 children (mean age: 5.8 years; range: 2.4-10.5 years) admitted to a university hospital because of clinical symptoms of OSAS. Their sleep was monitored with a 6-channel computerized polygraph. Data on anthropometry and circulating concentrations of IGF-I and IGFBP-3 were generated and compared with corresponding characteristics in control children (N = 35). Thirty children with an obstructive apnea-hypopnea index (OAHI) of 1 or more were categorized as children with OSAS (mean OAHI: 5.4 [95% confidence interval for mean (CI): 3.8-6.9]), whereas 40 children with an OAHI of <1 were considered as primary snorers (PS) (mean OAHI 0.13 [95% CI: 0.05-0.21]). Nineteen children with OAHI >2 underwent adenotonsillectomy attributable to OSAS and were reassessed 6 months later together with 34 nonoperated children with OAHI <2.

RESULTS

There were no initial differences in relative height and weight for height between the 3 groups of children. No differences were observed in peripheral IGF-I concentrations, but both OSAS and PS children had reduced peripheral IGFBP-3 levels. The operated children with initial OSAS experienced a highly significant reduction in their OAHI from 7.1 (95% CI: 5.1-9.1) to 0.37 (95% CI: 0.2-0.95). Weight-for-height, body mass index, body fat mass, and fat-free mass increased during the follow-up in the operated children with OSAS, whereas only fat-free mass and relative height increased in the PS children. Both the IGF-I and the IGFBP-3 concentrations increased significantly in the operated children, whereas no significant changes were seen in the PS children.

CONCLUSIONS

These observations indicate that growth hormone secretion is impaired in children with OSAS and PS. Respiratory improvement after adenotonsillectomy in children with OSAS results in weight gain and restored growth hormone secretion.

Reduced levels of growth hormone, insulin-like growth factor-I and binding protein-3 in patients with shunted hydrocephalus

OBJECTIVE

Children with hydrocephalus are characterised by slow linear growth in prepuberty, accelerated physical maturation during puberty, and reduced final height. We aimed to study the possible roles of growth hormone, insulin-like growth factor-I (IGF-I), and IGF binding protein-3 (IGFBP-3) in this growth pattern.

STUDY DESIGN

One hundred and fourteen patients with shunted hydrocephalus (62 males) aged 5 to 20 years, of whom 17 had spina bifida (six males), and 73 healthy controls (38 males) were studied. Anthropometric measures, body mass index, and body fat mass were assessed and the stage of puberty was determined. Serum growth hormone and plasma IGF-I and IGFBP-3 concentrations were measured.

RESULTS

The patients comprised 44 (26 males) who were prepubertal and 70 (36 males) pubertal or postpubertal, while 32 of the controls (19 males) were prepubertal and 41 (19 males) pubertal or postpubertal. The prepubertal children with hydrocephalus had lower IGF-I (p = 0.002) and IGFBP-3 concentrations (p < 0.001) than the controls, and the pubertal children had four times lower basal growth hormone concentrations (p < 0.001). There was a correlation between height SD score and IGF-I levels in the total patient population (r = 0.23; p = 0.01). Peripheral IGF-I concentrations peaked at pubertal stages 2-3 in the female patients and at stage 4 in the controls. The prepubertal patients on antiepileptic treatment, carbamazepine in most cases (73%), had higher IGF-I (p = 0.01) and IGFBP-3 concentrations (p = 0.03) than those who had never been treated with antiepileptic drugs, but still lower IGFBP-3 levels than the controls (p = 0.01).

CONCLUSION

Based on these findings, it can be concluded that reduced growth hormone secretion may contribute to the pattern of slow linear growth and reduced final height observed in these patients.

Minor head injury

Head injury is common in children, although the incidence of brain injury is much lower. Most children who sustain an injury to the head will only have a minor injury. Careful history, examination, and judicious use of radiology will identify those children at risk of brain injury. Children with no significant risk of brain injury may be safely discharged home to the care of responsible adults. Further work is needed to address sequelae after minor head injury.

Recombinant growth hormone: a new cardiovascular drug therapy

GH has an important role in normal cardiovascular physiologic functioning, working indirectly through effects on IGF-1. An excess or deficiency of GH causes an increased rate of cardiovascular disease, including cardiomyopathy. A relative GH deficiency in older subjects may also increase cardiovascular morbidity and mortality risk. In replacement doses, GH can enhance myocardial contractility; can decrease peripheral vascular resistance; and can reduce total cholesterol and LDL-cholesterol values and fibrinogen and PAI levels. These effects of GH, coupled with the ability to improve skeletal muscle function and reduce adiposity, make it an attractive treatment for patients with CHF and a potential maintenance drug for elderly people. Clinical trials, including studies with GHRH that may reduce the adverse effects of GH therapy, such as hyperglycemia and hypertension, are now in progress.