Deregulation of the growth hormone/insulin-like growth factor-1 axis in adults with cystic fibrosis

Endocrine Complications of Cystic Fibrosis

Endocrine comorbidities have become increasingly important medical considerations as improving cystic fibrosis (CF) care increases life expectancy. Although the underlying pathophysiology of CF-related diabetes remains elusive, the use of novel technologies and therapeutics seeks to improve both CF-related outcomes and quality of life. Improvements in the overall health of those with CF have tempered concerns about pubertal delay and short stature; however, other comorbidities such as hypogonadism and bone disease are increasingly recognized. Following the introduction of highly effective modulator therapies there are many lessons to be learned about their long-term impact on endocrine comorbidities.

Biochemical discrepancies in the evaluation of the somatotroph axis: Elevated GH or IGF-1 levels do not always diagnose acromegaly

The most frequent diagnosis underlying the finding of an elevated growth hormone (GH) and insulin-like growth factor-1 (IGF-1) is acromegaly due to a GH-secreting pituitary tumour. However, GH and IGF-1 levels can be discordant in patients with acromegaly due to early or partially treated disease, or there might be another cause of high GH or high IGF-1 unrelated to acromegaly, such as pre-analytical and technical pitfalls, physiological circumstances and pathological conditions. High GH and normal or low serum IGF-1, or alternatively, normal GH with elevated serum IGF-1, should be carefully assessed to avoid misinterpreting the activity of acromegaly or misdiagnosing a patient with acromegaly. We summarise here these biochemical discrepancies in the evaluation of the somatotroph axis.

Evaluation of growth hormone deficiency in children with cystic fibrosis

Background:

Due to chronic respiratory and gastrointestinal problems, growth failure is a common issue in patients with cystic fibrosis (CF). The present study aimed to investigate the prevalence of growth hormone deficiency (GHD) in CF children with stable gastrointestinal and respiratory conditions.

Materials and Methods:

In this study, the growth indicators of all 4–16-year-old children referred to two CF clinics were monitored over 3 years. Children without severe gastrointestinal or pulmonary symptoms with weight <3% percentile or whose height increase were two standard deviations below their expected height growth over 6 months were selected for the growth hormone (GH) stimulation test by clonidine and L-dopa test. Some of the children without CF, who were also referred for height growth disorders and matched the CF group, were considered the control group. They underwent the GH stimulation test, and the results were compared.

Results:

From 150 patients with CF, growth failure was observed in 24 patients with stable gastrointestinal and respiratory conditions; in 10 of them, the GH stimulation test was deficient. The prevalence of GHD was 6.6% in CF patients. In the control group of 30 children without CF, but with growth failure, the GH was deficient in nine cases, implying no significant difference with the case group (P = 0.37).

Conclusion:

In our study, the prevalence of GHD was 6.6% in CF patients, whereas the prevalence GHD in the normal population of childhood is <1%. Therefore, further studies should be designed to investigate the cause of GHD in CF patients.

Current and novel therapeutic strategies for the management of cystic fibrosis

Introduction: Cystic fibrosis (CF), is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and affects thousands of people throughout the world. Lung disease is the leading cause of death in CF patients. Despite the advances in treatments, the management of CF mainly targets symptoms. Recent CFTR modulators however target common mutations in patients, alleviating symptoms of CF. Unfortunately, there is still no approved treatments for patients with rare mutations to date.Areas covered: This paper reviews current treatments of CF that mitigate symptoms and target genetic defects. The use of gene and drug delivery systems such as viral or non-viral vectors and nano-compounds to enhance CFTR expression and the activity of antimicrobials against chronic pulmonary infections respectively, will also be discussed.Expert opinion: Nano-compounds tackle biological barriers to drug delivery and revitalize antimicrobials, anti-inflammatory drugs and even genes delivery to CF patients. Gene therapy and gene editing are of particular interest because they have the potential to directly target genetic defects. Nanoparticles should be formulated to more specifically target epithelial cells, and biofilms. Finally, the development of more potent gene vectors to increase the duration of gene expression and reduce inflammation is a promising strategy to eventually cure CF.

Activated L-Arginine/Nitric Oxide Pathway in Pediatric Cystic Fibrosis and Its Association with Pancreatic Insufficiency, Liver Involvement and Nourishment: An Overview and New Results

Cystic fibrosis (CF; OMIM 219700) is a rare genetic disorder caused by a chloride channel defect, resulting in lung disease, pancreas insufficiency and liver impairment. Altered L-arginine (Arg)/nitric oxide (NO) metabolism has been observed in CF patients’ lungs and in connection with malnutrition. The aim of the present study was to investigate markers of the Arg/NO pathway in the plasma and urine of CF patients and to identify possible risk factors, especially associated with malnutrition. We measured the major NO metabolites nitrite and nitrate, Arg, a semi-essential amino acid and NO precursor, the NO synthesis inhibitor asymmetric dimethylarginine (ADMA) and its major urinary metabolite dimethylamine (DMA) in plasma and urine samples of 70 pediatric CF patients and 78 age-matched healthy controls. Biomarkers were determined by gas chromatography–mass spectrometry and high-performance liquid chromatography. We observed higher plasma Arg (90.3 vs. 75.6 µM, p < 0.0001), ADMA (0.62 vs. 0.57 µM, p = 0.03), Arg/ADMA ratio (148 vs. 135, p = 0.01), nitrite (2.07 vs. 1.95 µM, p = 0.03) and nitrate (43.3 vs. 33.1 µM, p < 0.001) concentrations, as well as higher urinary DMA (57.9 vs. 40.7 µM/mM creatinine, p < 0.001) and nitrate (159 vs. 115 µM/mM creatinine, p = 0.001) excretion rates in the CF patients compared to healthy controls. CF patients with pancreatic sufficiency showed plasma concentrations of the biomarkers comparable to those of healthy controls. Malnourished CF patients had lower Arg/ADMA ratios (p = 0.02), indicating a higher NO synthesis capacity in sufficiently nourished CF patients. We conclude that NO production, protein-arginine dimethylation, and ADMA metabolism is increased in pediatric CF patients. Pancreas and liver function influence Arg/NO metabolism. Good nutritional status is associated with higher NO synthesis capacity and lower protein-arginine dimethylation.

Impact of Pituitary Autoimmunity and Genetic Disorders on Growth Hormone Deficiency in Children and Adults

Growth hormone (GH), mostly through its peripheral mediator, the insulin-like growth factor 1(IGF1), in addition to carrying out its fundamental action to promote linear bone growth, plays an important role throughout life in the regulation of intermediate metabolism, trophism and function of various organs, especially the cardiovascular, muscular and skeletal systems. Therefore, if a prepubertal GH secretory deficiency (GHD) is responsible for short stature, then a deficiency in adulthood identifies a nosographic picture classified as adult GHD syndrome, which is characterized by heart, muscle, bone, metabolic and psychic abnormalities. A GHD may occur in patients with pituitary autoimmunity; moreover, GHD may also be one of the features of some genetic syndromes in association with other neurological, somatic and immune alterations. This review will discuss the impact of pituitary autoimmunity on GHD and the occurrence of GHD in the context of some genetic disorders. Moreover, we will discuss some genetic alterations that cause GH and IGF-1 insensitivity and the arguments in favor and against the influence of GH/IGF-1 on longevity and cancer in the light of the papers on these issues that so far appear in the literature.

GH-IGF-1 Axis in Children with Cystic Fibrosis

OBJECTIVE

To verify whether growth hormone receptor (GHR) gene expression plays a role in growth of children with cystic fibrosis (CF), as a consequence of the chronic inflammatory condition and malnutrition.

DESIGN

We enrolled 49 prepubertal patients (24 males and 25 females) affected by CF in a stable clinical condition, 19 of whom had been diagnosed through newborn screening and 30 following presentation of symptoms. Patients had no significant comorbidity affecting growth or cystic fibrosis transmembrane conductance regulator (CFTR)-related diabetes requiring insulin therapy. Blood was collected during two follow-up visits to measure insulin-like growth factor (IGF-I), growth hormone-binding protein (GHBP), and GHR gene expression. Recruited as a control group were 52 healthy children, sex- and age-matched, were recruited as a control group.

METHODS

We compared body mass index (BMI), height, weight, IGF-I, GHBP, and GHR gene expression values (evaluated by Chemiluminescent Immunometric assay; ELISA and real-time PCR, respectively) in CF patients diagnosed through newborn screening (NBS) or by symptoms (late diagnosis [LD]) and in healthy controls.

RESULTS

BMI increased significantly in patients between the time of diagnosis and check-up (P<0.001), particularly in the LD group; median value was lower at diagnosis and significantly higher (P<0.001) at follow-up visits compared to controls. At initial evaluation, higher levels of IGF-I (not statistically significant) were found in both the NBS group and the LD group compared to the control group. At the second evaluation, significantly higher levels of IGF-I (P=0.003) were found in both the NBS and LD groups compared to controls; GHR mRNA expression had significantly increased (P=0.013) in LD patients compared with the first evaluation and was significantly higher in the NBS and LD groups than in controls. GHBP values had significantly increased (P=0.047) in the NBS group after one year of therapy compared to first visit levels and were significantly higher (P<0,0001) in the NBS and LD groups compared to controls.

CONCLUSION

In our LD patients during childhood, we observed good auxological values and a GH/IGF-I axis function within normal range for the factor evaluated. However, earlier diagnosis through NBS might further minimize and prevent growth retardation, by reducing the duration of symptoms before treatment.

Impact of CFTR-modulating drugs on GH-IGF-1 axis impairment in adult patients with cystic fibrosis

INTRODUCTION

A new class of drugs in the treatment of cystic fibrosis (CF) includes two agents: lumacaftor, which corrects CFTR channel protein, and ivacaftor, which increases CFTR channel activity. In our previous study we recruited 50 stable adults with CF and 16 of them showed growth hormone deficit (GHD): 7 patients severe and 9 patients partial GHD.

MATERIAL AND METHODS

We decided to re-evaluate ten patients with the GHRH + arginine test of whom only five were treated with lumacaftor/ivacaftor.

RESULTS

All CF patients in therapy with lumacaftor/ivacaftor showed a marked improvement in GHD. Two patients moved from a severe GHD to a normal response to the GH/IGF-1 axis test, and three patients who had partial GHD moved to normal response.

CONCLUSION

The pituitary gland may be damaged by CF disease and could benefit of the action of correcting drugs.