Insulin-like growth factor-I levels predict weight, height and protein catabolism in children and adolescents with cystic fibrosis

Appetite stimulants for people with cystic fibrosis

BACKGROUND

Chronic loss of appetite in cystic fibrosis concerns both individuals and families. Appetite stimulants have been used to help cystic fibrosis patients with chronic anorexia attain optimal body mass index (BMI) and nutritional status. However, these may have adverse effects on clinical status. This is an updated version of the original review.

OBJECTIVES

To systematically search for and evaluate the evidence on the beneficial effects of appetite stimulants in the management of cystic fibrosis-related anorexia and synthesise reports of any side effects.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Cystic Fibrosis Trials Register and online trials registries; handsearched reference lists; and contacted local and international experts to identify relevant trials. Last search of the Cystic Fibrosis Trials Register: 23 May 2022. Last search of online trial registries: 10 May 2022.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials of appetite stimulants compared to placebo, control, no treatment or different appetite stimulants, or to the same appetite stimulants at different doses or regimens for at least one month in adults and children with cystic fibrosis.

DATA COLLECTION AND ANALYSIS

Review authors independently extracted data and assessed risk of bias of the included trials. We used the GRADE approach to assess the certainty of the evidence and performed meta-analyses.

MAIN RESULTS

We included four trials (70 participants) comparing appetite stimulants (cyproheptadine hydrochloride and megestrol acetate) to placebo; the numbers of adults or children within each trial were not always reported. We assessed the certainty of evidence as low due to the small number of participants, incomplete or selective outcome reporting, and unclear risk of selection bias.  Regarding our primary outcomes, a meta-analysis of two trials (42 participants) showed that appetite stimulants may produce a larger increase in weight (kg) at three months (mean difference (MD) 1.25 kg, 95% confidence interval (Cl) 0.45 to 2.05), and one trial (17 participants) showed a similar result at six months (MD 3.80 kg, 95% CI 1.27 to 6.33) (both low-certainty evidence). Results also showed that weight z score may increase with appetite stimulants compared to placebo at three months (MD 0.61, 95% CI 0.29 to 0.93; 3 studies; 40 participants; P < 0.001) and at six months (MD 0.74, 95% CI 0.26 to 1.22; 1 trial; 17 participants). There was no evidence of a difference in effect between cyproheptadine hydrochloride and megestrol acetate for either outcome.   Only one trial (25 participants) reported analysable data for body composition (BMI), with results favouring cyproheptadine hydrochloride compared to placebo; a further trial (16 participants) narratively agreed with this result. All four trials reported on lung function at durations ranging from two to nine months. Considering analysable data, two trials (42 participants) found that appetite stimulants may make little or no difference in forced expiratory volume at one second (FEV1) % predicted at three months, and one trial (17 participants) found similar results at six months. Two further three-month trials narratively agreed with these results. Limited information was reported for secondary outcomes. Two trials (23 participants) reported results showing that appetite stimulants may increase appetite compared to placebo at three months (odds ratio 45.25, 95% CI 3.57 to 573.33; low-certainty evidence).  Only one study reported on quality of life, finding that cyproheptadine reduced fatigue in two participants compared with none with placebo. One study (25 participants) found no difference in energy intake between appetite stimulant or placebo at three months. Insufficient reporting of adverse effects prevented a full determination of their impact. Two studies (33 participants) narratively reported similar requirements for additional antibiotics between appetite stimulants and placebo at three months.  AUTHORS' CONCLUSIONS: At six months in adults and children, appetite stimulants improved only two of the outcomes of this review: weight (or weight z score) and subjectively reported appetite. Insufficient reporting of side effects prevented a full determination of their impact. Whilst the data may suggest the potential use of appetite stimulants in treating anorexia in adults and children with cystic fibrosis, this is based upon low-certainty evidence from a small number of trials, therefore firm conclusions cannot be drawn. Clinicians need to be aware of the potential adverse effects of appetite stimulants and actively monitor any individuals prescribed these medications accordingly. Research is required to determine meaningful surrogate measures for appetite and to define what constitutes quality weight gain. Future trials of appetite stimulants should use a validated measure of symptoms including a disease-specific instrument for measuring poor appetite. This review highlights the need for multicentred, adequately powered, and well-designed trials to evaluate agents to safely increase appetite in people with cystic fibrosis and to establish the optimal mode of treatment.

HDAC6 depletion improves cystic fibrosis mouse airway responses to bacterial challenge

The hypothesis of this study was that Hdac6 depletion would restore cystic fibrosis (CF) responses to bacterial challenge to more wild type profiles using a CF mouse model. CF mice harboring the F508del Cftr mutation respond to bacterial challenge with 25,000 CFU Pseudomonas aeruginosa embedded into agarose beads to slow clearance. CF mice respond significantly more aggressively to this challenge compared to WT mice with respect to bacterial clearance, weight loss, neutrophil recruitment, and MIP-2 production. Depletion of Hdac6 expression in the CF mice (CF/Hdac6) significantly improves these responses to more WT levels. Weight loss in response to infection is most severe in CF mice and significantly attenuated in CF/Hdac6 mice. Bacterial levels are reduced at a faster rate in CF/Hdac6 mice compared to CF mice where infection persists. Percent neutrophils in lung lavage fluid post-infection are significantly higher in CF mice, but returned to WT levels with CF/Hdac6 mice. Similarly, CF Mip-2 levels are restored to WT levels in the absence of Hdac6 expression. These data demonstrate that Hdac6 depletion restores CF responses to bacterial challenge to WT-like profiles and offer a potential therapeutic avenue for addressing inflammation and infection in CF airways independently of Cftr correction.

Insulin-Like Growth Factor-1 Signaling in Lung Development and Inflammatory Lung Diseases

Insulin-like growth factor-1 (IGF-1) was firstly identified as a hormone that mediates the biological effects of growth hormone. Accumulating data have indicated the role of IGF-1 signaling pathway in lung development and diseases such as congenital disorders, cancers, inflammation, and fibrosis. IGF-1 signaling modulates the development and differentiation of many types of lung cells, including airway basal cells, club cells, alveolar epithelial cells, and fibroblasts. IGF-1 signaling deficiency results in alveolar hyperplasia in humans and disrupted lung architecture in animal models. The components of IGF-1 signaling pathways are potentiated as biomarkers as they are dysregulated locally or systemically in lung diseases, whereas data may be inconsistent or even paradoxical among different studies. The usage of IGF-1-based therapeutic agents urges for more researches in developmental disorders and inflammatory lung diseases, as the majority of current data are collected from limited number of animal experiments and are generally less exuberant than those in lung cancer. Elucidation of these questions by further bench-to-bedside researches may provide us with rational clinical diagnostic approaches and agents concerning IGF-1 signaling in lung diseases.

Reduced bone length, growth plate thickness, bone content, and IGF-I as a model for poor growth in the CFTR-deficient rat

Background

Reduced growth and osteopenia are common in individuals with cystic fibrosis (CF). Additionally, improved weight and height are associated with better lung function and overall health in the disease. Mechanisms for this reduction in growth are not understood. We utilized a new CFTR knockout rat to evaluate growth in young CF animals, via femur length, microarchitecture of bone and growth plate, as well as serum IGF-I concentrations.

Methods

Femur length was measured in wild-type (WT) and SD-CFTR^tm1sage (Cftr-/-) rats, as a surrogate marker for growth. Quantitative bone parameters in Cftr-/- and WT rats were measured by micro computed tomography (micro-CT). Bone histomorphometry and cartilaginous growth plates were analyzed. Serum IGF-I concentrations were also compared.

Results

Femur length was reduced in both Cftr-/- male and female rats compared to WT. Multiple parameters of bone microarchitecture (of both trabecular and cortical bone) were adversely affected in Cftr-/- rats. There was a reduction in overall growth plate thichkness in both male and female Cftr-/- rats, as well as hypertrophic zone thickness and mean hypertrophic cell volume in male rats, indicating abnormal growth characteristics at the plate. Serum IGF-I concentrations were severely reduced in Cftr-/- rats compared to WT littermates.

Conclusions

Despite absence of overt lung or pancreatic disease, reduced growth and bone content were readily detected in young Cftr-/- rats. Reduced size of the growth plate and decreased IGF-I concentrations suggest the mechanistic basis for this phenotype. These findings appear to be intrinsic to the CFTR deficient state and independent of significant clinical confounders, providing substantive evidence for the importance of CFTR on maintinaing normal bone growth.

Bone disease in cystic fibrosis: new pathogenic insights opening novel therapies

Mutations within the gene encoding for the chloride ion channel cystic fibrosis transmembrane conductance regulator (CFTR) results in cystic fibrosis (CF), the most common lethal autosomal recessive genetic disease that causes a number of long-term health problems, as the bone disease. Osteoporosis and increased vertebral fracture risk associated with CF disease are becoming more important as the life expectancy of patients continues to improve. The etiology of low bone density is multifactorial, most probably a combination of inadequate peak bone mass during puberty and increased bone losses in adults. Body mass index, male sex, advanced pulmonary disease, malnutrition and chronic therapies are established additional risk factors for CF-related bone disease (CFBD). Consistently, recent evidence has confirmed that CFTR plays a major role in the osteoprotegerin (OPG) and COX-2 metabolite prostaglandin E2 (PGE2) production, two key regulators in the bone formation and regeneration. Several others mechanisms were also recognized from animal and cell models contributing to malfunctions of osteoblast (cell that form bone) and indirectly of bone-resorpting osteoclasts. Understanding such mechanisms is crucial for the development of therapies in CFBD. Innovative therapeutic approaches using CFTR modulators such as C18 have recently shown in vitro capacity to enhance PGE2 production and normalized the RANKL-to-OPG ratio in human osteoblasts bearing the mutation F508del-CFTR and therefore potential clinical utility in CFBD. This review focuses on the recently identified pathogenic mechanisms leading to CFBD and potential future therapies for treating CFBD.

Growth and the Growth Hormone-Insulin Like Growth Factor 1 Axis in Children With Chronic Inflammation: Current Evidence, Gaps in Knowledge, and Future Directions

Growth failure is frequently encountered in children with chronic inflammatory conditions like juvenile idiopathic arthritis, inflammatory bowel disease, and cystic fibrosis. Delayed puberty and attenuated pubertal growth spurt are often seen during adolescence. The underlying inflammatory state mediated by proinflammatory cytokines, prolonged use of glucocorticoid, and suboptimal nutrition contribute to growth failure and pubertal abnormalities. These factors can impair growth by their effects on the GH-IGF axis and also directly at the level of the growth plate via alterations in chondrogenesis and local growth factor signaling. Recent studies on the impact of cytokines and glucocorticoid on the growth plate further advanced our understanding of growth failure in chronic disease and provided a biological rationale of growth promotion. Targeting cytokines using biological therapy may lead to improvement of growth in some of these children, but approximately one-third continue to grow slowly. There is increasing evidence that the use of relatively high-dose recombinant human GH may lead to partial catch-up growth in chronic inflammatory conditions, although long-term follow-up data are currently limited. In this review, we comprehensively review the growth abnormalities in children with juvenile idiopathic arthritis, inflammatory bowel disease, and cystic fibrosis, systemic abnormalities of the GH-IGF axis, and growth plate perturbations. We also systematically reviewed all the current published studies of recombinant human GH in these conditions and discussed the role of recombinant human IGF-1.

Usefulness of insulin like growth factor 1 as a marker of heart failure in children and young adults after the Fontan palliation procedure

Growth hormone and its mediator, insulinlike growth factor 1 (IGF-1), are key determinants of growth in children and young adults. As patients with Fontan physiology often experience diminished longitudinal growth, we sought to describe IGF-1 levels in this population and to identify factors associated with IGF-1 deficiency. Forty-one Fontan subjects ≥5 years were evaluated in this cross-sectional study. Age- and gender-specific height Z scores were generated using national data. Laboratory testing included IGF-1 and brain natriuretic peptide (BNP) levels. IGF-1 levels were converted to age-, gender-, and Tanner stage-specific Z scores. BNP levels were log transformed to achieve a normal distribution (log-BNP). Medical records were reviewed for pertinent clinical variables. Predictors of IGF-1 Z score were assessed through the Student t test and Pearson's correlation. Median age was 11.1 years (range 5.1 to 33.5 years), and time from Fontan was 8.2 years (1.1 to 26.7). Mean height Z score was -0.2 ± 0.9 with a mean IGF-1 Z score of -0.1 ± 1.3. There was no association between IGF-1 Z score and height Z score. Longer interval since Fontan (R = -0.32, p = 0.04), higher log-BNP (R = -0.40; p = 0.01), and lower indexed systemic flow on cardiac magnetic resonance (R = 0.55, p = 0.02) were associated with lower IGF-1 Z scores. In conclusion, in this cohort with Fontan physiology, higher BNP and lower systemic flow were associated with lower IGF-1 Z score. Longitudinal studies are needed to determine if these relations represent a mechanistic explanation for diminished growth in children with this physiology and with other forms of congenital heart disease.

Appetite stimulants for people with cystic fibrosis

BACKGROUND

Chronic loss of appetite in cystic fibrosis concerns both individuals and families. Appetite stimulants have been used to help cystic fibrosis patients with chronic anorexia attain optimal body mass index and nutritional status. However, these may have adverse effects on clinical status.

OBJECTIVES

The aim of this review is to systematically search for and evaluate evidence on the beneficial effects of appetite stimulants in the management of CF-related anorexia and synthesize reports of any side-effects.

SEARCH METHODS

Trials were identified by searching the Cochrane Cystic Fibrosis and Genetic Disorders Group's Cystic Fibrosis Trials Register, MEDLINE, Embase, CINAHL, handsearching reference lists and contacting local and international experts.Last search of online databases: 01 April 2014.Last search of the Cystic Fibrosis Trials Register: 08 April 2014.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials of appetite stimulants, compared to placebo or no treatment for at least one month in adults and children with cystic fibrosis.

DATA COLLECTION AND ANALYSIS

Authors independently extracted data and assessed the risk of bias within eligible trials. Meta-analyses were performed.

MAIN RESULTS

Three trials (total of 47 recruited patients) comparing appetite stimulants (cyproheptadine hydrochloride and megesterol acetate) to placebo were included; the numbers of adults or children within each trial were not always reported. The risk of bias of the included trials was graded as moderate.A meta-analysis of all three trials showed appetite stimulants produced a larger increase in weight z score at three months compared to placebo, mean difference 0.61 (95% confidence interval 0.29 to 0.93) (P < 0.001) (n = 40) with no evidence of a difference in effect between two different appetite stimulants. One of these trials also reported a significant weight increase with megesterol acetate compared to placebo at six months (n = 17). The three trials reported no significant differences in forced expiratory volume at one second (per cent predicted) between the appetite stimulant groups and placebo at follow up, with durations ranging from two to nine months. A meta-analysis of two trials showed a significantly higher proportion of patients reporting increased appetite, odds ratio 45.25 (95% confidence interval 3.57 to 573.33) (P = 0.003) (n = 23), but the frequency of reported side effects was undetermined.

AUTHORS' CONCLUSIONS

In the short term (six months) in adults and children, appetite stimulants improved only two of the outcomes in this review - weight (or weight z score) and appetite; and side effects were insufficiently reported to determine the full extent of their impact. Whilst the data may suggest the potential use of appetite stimulants in treating anorexia in adults and children with cystic fibrosis, this is based upon moderate quality data from a small number of trials and so this therapy cannot be conclusively recommended based upon the findings in the review. Clinicians need to be aware of the potential adverse effects of appetite stimulants and actively monitor any patients prescribed these medications accordingly.Research is needed to determine meaningful surrogate measures for appetite and define what constitutes quality weight gain. Future trials of appetite stimulants should use a validated measure of symptoms including a disease-specific instrument for measuring poor appetite. This review highlights the need for multicentred, adequately powered and well-designed trials to evaluate agents to safely increase appetite in people with cystic fibrosis and to establish the optimal mode of treatment.

IGF-I increases markers of osteoblastic activity and reduces bone resorption via osteoprotegerin and RANK-ligand

Background

Bone is one of the major target tissues for Insulin-like Growth Factor I (IGF-I). Low doses of IGF-I were able to improve liver-associated osteopenia. In the present work, a model of partial IGF-I deficiency was used in order to provide insight into the mechanisms of the beneficial actions of IGF-I replacement therapy in bone.

Methods

Several proteins involved in osteoblastic/osteocyte and osteoclastic differentiation and activity were studied in the three experimental groups: control (CO) group (wild type mice, Igf^+/+, n = 10), heterozygous Igf^+/- group with partial IGF-I deficiency (Hz, n = 10), and heterozygous Igf^+/- mice treated with IGF-I for 10 days (Hz + IGF-I, n = 10).

Results

Data in this paper confirm that the simple partial IGF-I deficiency is responsible for osteopenia, determined by densitometry and histopathology. These findings are associated with a reduced gene expression of osteoprotegerin, sclerostin, calcitonin receptor (CTR), insulin-like growth factor binding protein 5 and RUNX2. IGF-I replacement therapy normalized CTR gene expression and reduced markers of osteoclastic activity.

Conclusions

Low doses of IGF-I constituted a real replacement therapy that normalized IGF-I serum levels improving the expression of most of these proteins closely involved in bone-forming, and reducing bone resorption by mechanisms related to osteoprotegerin, RANKL and PTH receptor.

Low levels of insulin-like growth factor-1 contribute to alveolar macrophage dysfunction in cystic fibrosis

Alveolar macrophages are major contributors to lung innate immunity. Although alveolar macrophages from cystic fibrosis (CF) transmembrane conductance regulator(-/-) mice have impaired function, no study has investigated primary alveolar macrophages in adults with CF. CF patients have low levels of insulin-like growth factor 1 (IGF-1), and our prior studies demonstrate a relationship between IGF-1 and macrophage function. We hypothesize that reduced IGF-1 in CF leads to impaired alveolar macrophage function and chronic infections. Serum and bronchoalveolar lavage (BAL) samples were obtained from eight CF subjects and eight healthy subjects. Macrophages were isolated from BAL fluid. We measured the ability of alveolar macrophages to kill Pseudomonas aeruginosa. Subsequently, macrophages were incubated with IGF-1 prior to inoculation with bacteria to determine the effect of IGF-1 on bacterial killing. We found a significant decrease in bacterial killing by CF alveolar macrophages compared with control subjects. CF subjects had lower serum and BAL IGF-1 levels compared with healthy control subjects. Exposure to IGF-1 enhanced alveolar macrophage macrophages in both groups. Finally, exposing healthy alveolar macrophages to CF BAL fluid decreased bacterial killing, and this was reversed by the addition of IGF-1, whereas IGF-1 blockade worsened bacterial killing. Our studies demonstrate that alveolar macrophage function is impaired in patients with CF. Reductions in IGF-1 levels in CF contribute to the impaired alveolar macrophage function. Exposure to IGF-1 ex vivo results in improved function of CF alveolar macrophages. Further studies are needed to determine whether alveolar macrophage function can be enhanced in vivo with IGF-1 treatment.

The impact of dysglycaemia on bone mineral accrual in young people with cystic fibrosis

OBJECTIVE

The effect of dysglycaemia on bone mineral density (BMD) has not been studied in young people with CF. We examined factors associated with BMD in a tertiary paediatric CF clinic.

DESIGN

Retrospective, clinic-based study at The Children's Hospital at Westmead, Sydney.

PATIENTS

Young people with CF aged ≤ 18 years.

MEASUREMENTS

Bone mineral density was measured by dual-energy X-ray absorptiometry; main outcome measures were total body (TB), lumbar spine (LS) and femoral neck (FN) BMD and bone mineral content (BMC), and LS volumetric BMD (vBMD), reported as z scores for height. Dysglycaemia, based on oral glucose tolerance test, was defined as CF-related diabetes (CFRD) or impaired glucose tolerance (IGT).

RESULTS

Overall, 14 of 81 (17%) had CFRD, 6 (7%) IGT and 61 (76%) normal glucose tolerance (NGT). Mean age was 14.9 ± 2.4 years and mean height z score -0.68 ± 1.39. Osteopenic (z score ≤-2) TB, LS or FN BMD was present in 30 of 81 (37%), BMC in 42 (52%) and vBMD in 10 (5%). Across the three groups, there were differences in LS vBMD (CFRD, -0.67 ± 0.76; IGT, -0.52 ± 0.76; NGT, -0.05 ± 1.39; P = 0.04), LS BMD (P < 0.01), LS BMC (P = 0.01) and TB BMD (P = 0.01). In multivariate linear regression, LS BMC was associated with dysglycaemia (β = 0.56; 95% CI, 0.00-1.13; P = 0.05) and approached significance for FEV(1) (β = 0.01; 95% CI, 0.00-0.02; P = 0.06).

CONCLUSIONS

Dysglycaemia is associated with reduced bone mass accrual in youth with CF, in addition to recognized factors such as abnormal lung function, poor nutritional status and disease severity. Bone health assessment is essential in youth with CF.

Human conditions of insulin-like growth factor-I (IGF-I) deficiency

Insulin-like growth factor I (IGF-I) is a polypeptide hormone produced mainly by the liver in response to the endocrine GH stimulus, but it is also secreted by multiple tissues for autocrine/paracrine purposes. IGF-I is partly responsible for systemic GH activities although it possesses a wide number of own properties (anabolic, antioxidant, anti-inflammatory and cytoprotective actions). IGF-I is a closely regulated hormone. Consequently, its logical therapeutical applications seems to be limited to restore physiological circulating levels in order to recover the clinical consequences of IGF-I deficiency, conditions where, despite continuous discrepancies, IGF-I treatment has never been related to oncogenesis. Currently the best characterized conditions of IGF-I deficiency are Laron Syndrome, in children; liver cirrhosis, in adults; aging including age-related-cardiovascular and neurological diseases; and more recently, intrauterine growth restriction. The aim of this review is to summarize the increasing list of roles of IGF-I, both in physiological and pathological conditions, underlying that its potential therapeutical options seem to be limited to those proven states of local or systemic IGF-I deficiency as a replacement treatment, rather than increasing its level upper the normal range.

How height is related to our health and longevity: a review

Most people believe that being taller and heavier is a sign of higher social status and privilege; however, an objective evaluation of the advantages and disadvantages of increased body size (excluding obesity) indicated that shorter, smaller bodies have numerous advantages in terms of health and longevity. With healthful nutrition and lifestyles, and good medical care, shorter people are less likely to suffer from age-related chronic diseases and more likely to reach advanced ages. A variety of biological factors explain the inherent benefits of smaller bodies. These include reduced cell replication, much lower DNA damage and reduced cancer incidence. Other beneficial factors include higher sex hormone binding globulin, higher insulin-like growth factor binding protein-1, lower insulin and lower insulin-like growth factor-1. We discuss recommendations for how taller people can minimize their risks. Future public health practices should focus on healthful nutrition, without promoting continued secular growth in height and weight.

Growth retardation and reduced growth hormone secretion in cystic fibrosis. Clinical observations from three CF centers

OBJECTIVE

Growth delay in cystic fibrosis is frequent and is usually the result of several interacting causes. It most often derives from severe respiratory impairment and severe malabsorption. There are however patients whose clinical condition is not severe enough to be held accountable for this phenomenon. We aimed at describing patients who showed growth delay, who were not affected by severe pulmonary disease or malabsorption and who, when tested, showed a reduced GH secretion after stimulation with conventional agents. We noticed a disproportionately large prevalence of growth hormone (GH) release deficit (GHRD) in pediatric cystic fibrosis (CF) patients.

PATIENTS AND METHODS

We examined all patients under our care in the period 2006-11, who were older than 5 and younger than 16 years old. We focussed on those who fell below the 3rd height percentile, or whose growth during the previous 18 months faltered by >2SD, and who did not present clinical conditions that could reasonably explain their failure to thrive. These patients were subjected to standard GH provocative tests.

RESULTS

Out of 285 who matched the age criterion, 33 patients also matched the height percentile criterion. While 15/33 suffered clinical conditions that could reasonably explain their failure to thrive, 18/33 underwent GH release provocative tests and 12/18 showed a release deficit.

CONCLUSIONS

We conclude that impaired GH secretion is more frequent among CF patients compared to the prevalence of GH deficiency in the general population and that GH release impairment may be an independent cause of growth delay in CF. Our findings are in agreement with recent studies that have described low GH levels in CF piglets and in neonates with CF [1].

Pigs and humans with cystic fibrosis have reduced insulin-like growth factor 1 (IGF1) levels at birth

People with cystic fibrosis (CF) exhibit growth defects. That observation has been attributed, in part, to decreased insulin-like growth factor 1 (IGF1) levels, and the reduction has been blamed on malnutrition and pulmonary inflammation. However, patients with CF already have a reduced weight at birth, a manifestation not likely secondary to poor nutrition or inflammation. We found that, like humans, CF pigs were smaller than non-CF littermates and had lower IGF1 levels. To better understand the basis of IGF1 reduction, we studied newborn pigs and found low IGF1 levels within 12 h of birth. Moreover, humerus length and bone mineral content were decreased, consistent with less IGF1 activity in utero. These findings led us to test newborn humans with CF, and we found that they also had reduced IGF1 levels. Discovering lower IGF1 levels in newborn pigs and humans indicates that the decrease is not solely a consequence of malnutrition or pulmonary inflammation and that loss of cystic fibrosis transmembrane conductance regulator function has a more direct effect. Consistent with this hypothesis, we discovered reduced growth hormone release in organotypic pituitary slice cultures of newborn CF pigs. These findings may explain the long-standing observation that CF newborns are smaller than non-CF babies and why some patients with good clinical status fail to reach their growth potential. The results also suggest that measuring IGF1 levels might be of value as a biomarker to predict disease severity or the response to therapeutics. Finally, they raise the possibility that IGF1 supplementation beginning in infancy might be beneficial in CF.