Patient Selection for IGF-I Therapy

Metabolic-endocrine disruption due to preterm birth impacts growth, body composition, and neonatal outcome

Despite optimized nutrition, preterm-born infants grow slowly and tend to over-accrete body fat. We hypothesize that the premature dissociation of the maternal-placental-fetal unit disrupts the maintenance of physiological endocrine function in the fetus, which has severe consequences for postnatal development. This review highlights the endocrine interactions of the maternal-placental-fetal unit and the early perinatal period in both preterm and term infants. We report on hormonal levels (including tissue, thyroid, adrenal, pancreatic, pituitary, and placental hormones) and nutritional supply and their impact on infant body composition. The data suggest that the premature dissociation of the maternal-placental-fetal unit leads to a clinical picture similar to panhypopituitarism. Further, we describe how the premature withdrawal of the maternal-placental unit, neonatal morbidities, and perinatal stress can cause differences in the levels of growth-promoting hormones, particularly insulin-like growth factors (IGF). In combination with the endocrine disruption that occurs following dissociation of the maternal-placental-fetal unit, the premature adaptation to the extrauterine environment leads to early and fast accretion of fat mass in an immature body. In addition, we report on interventional studies that have aimed to compensate for hormonal deficiencies in infants born preterm through IGF therapy, resulting in improved neonatal morbidity and growth. IMPACT: Preterm birth prematurely dissociates the maternal-placental-fetal unit and disrupts the metabolic-endocrine maintenance of the immature fetus with serious consequences for growth, body composition, and neonatal outcomes. The preterm metabolic-endocrine disruption induces symptoms resembling anterior pituitary failure (panhypopituitarism) with low levels of IGF-1, excessive postnatal fat mass accretion, poor longitudinal growth, and failure to thrive. Appropriate gestational age-adapted nutrition alone seems insufficient for the achievement of optimal growth of preterm infants. Preliminary results from interventional studies show promising effects of early IGF-1 supplementation on postnatal development and neonatal outcomes.

Detection of a novel single nucleotide polymorphism in IGF2 gene with a negative impact on egg production and body weight in Japanese quail (Coturnix japonica)

Background

Insulin-like growth factor 2 (IGF2) is one of three hormones that share high structural similarity to insulin. It is involved in several insulin-like growth-regulating and mitogenic activities. This study was conducted to genotype the coding regions of the IGF2 gene in Japanese quail (Coturnix japonica) using PCR-SSCP-sequencing, and to assess the possible association of the polymorphism of these regions with the main egg production traits. A total of 240 female birds with an equal number of three Japanese quail populations (Brown or BR, Black or BL, and White or WT) were included in this study.

Results

All the genotyped regions exerted no heterogeneity in their sequences with one exception detected in the exon 2. In this locus, a novel single nucleotide polymorphism (SNP) was detected in which “A” was substituted with “G” at 81 position with a silent effect (p.F79=SNP) on IGF2 protein. Association analyses indicated a significant (P < 0.05) relation of this SNP with egg number (EN) and bird weight (BW) in the analyzed populations, in which the birds with AG genotype had lower EN and BW than those with AA genotype. The p.F79=SNP was largely detected in the WT line than the other two lines.

Conclusion

The detected p.F79=SNP has a highly negative effect on EN and BW in Japanese quail. Thus, the implementation of the variations of the IGF2 gene can be a useful marker in the marker-assisted selection of Japanese quail. This is the first report to describe IGF2 gene variations in Japanese quail, which strongly suggests raising the birds from the BR line with AA genotype when breeders desire to raise Japanese quail for large-scale egg production.

The role of acid-labile subunit (ALS) in the modulation of GH-IGF-I action

Acid-labile subunit (ALS) deficiency (ACLSD) constitutes the first monogenic defect involving a member of the Insulin-like Growth Factor (IGF) binding protein system. The lack of ALS completely disrupts the circulating IGF system. Autocrine/paracrine action of local produced IGF-I could explain the mild effect on growth. In the present work we have revised the more relevant clinical and biochemical consequences of complete ACLSD in 61 reported subjects from 31 families. Low birth weight and/or length, reduced head circumference, height between -2 and -3 SD, pubertal delay and insulin resistance are commonly observed. Partial ACLSD could be present in children initially labeled as idiopathic short stature, presenting low IGF-I levels, suggesting that one functional IGFALS allele is insufficient to stabilize ternary complexes. Dysfunction of the GH-IGF axis observed in ACLSD may eventually result in increased risk for type-2 diabetes and tumor progression. Consequently, long term surveillance is recommended in these patients.

Baseline IGFBP - 3 as the Key Element to Predict Growth Response to Growth Hormone and IGF - 1 Therapy in Subjects with Non - GH Deficient Short Stature and IGF - 1 Deficiency

BACKGROUND

Short stature in children represents a heterogeneous group with different etiologies. Primary Insulin like growth factor 1 (IGF - 1) deficiency in short stature can present with normal or elevated growth hormone (GH) production. Currently there is no model that can reliably predict response to recombinant (r)GH therapy and/or rIGF - 1 therapy in children with non - GH deficient short stature.

HYPOTHESIS

Baseline Insulin like growth factor binding protein 3 (IGFBP - 3) along with ∆ IGF - 1 in the first 3 months of GH therapy level can be a marker of growth response to the rGH and/or rIGF - 1 therapy in children with non - growth hormone deficiency short stature.

OBJECTIVES

To study the relationship between baseline IGFBP - 3 and IGF - 1 levels and the response to rGH and rIGF - 1 therapy in children with short stature, normal GH secretion and low IGF - 1 SDS.

METHODS

43 children, age 9.07 ± 2.75 years with height -2.72 ± 0.7 SD and baseline IGF - 1 of -2.76 ± 0.58 SD, who passed the growth hormone releasing hormone (GHRH) stimulation test were included in a retrospective chart review. They were treated with rGH therapy with a mean dose of 0.46 ± 0.1 mg/kg/week. Growth velocity (GV), IGF - 1 and IGFBP - 3 levels were done at 3 and 6 months of therapy. Subjects with poor response to rGH after 6 months of therapy were switched to rIGF - 1 therapy at 0.24 mg/kg/day for the next 6 months. Subjects were divided according to their growth rate into responders to rGH (N = 23); non - responders to rGH, responders to rIGF - 1 (N = 14) and non - responders to rGH and rIGF-1 (N = 6).

RESULTS

There was no correlation between GV and peak GH level at GHRH test. Growth velocity positively correlated with ΔIGF - 1 SD among subjects treated with rGH therapy. Height SD positively correlated with IGFBP - 3 SD. Baseline IGFBP - 3 also inversely correlated with GH peak during GHRH test.

CONCLUSIONS

In subjects with short stature and low IGF - 1 level, baseline IGFBP - 3 levels can predict the growth response to rGH and/or rIGF - 1 therapy.

Heterozygous IGFALS gene variants in idiopathic short stature and normal children: impact on height and the IGF system

BACKGROUND

In acid-labile subunit (ALS)-deficient families, heterozygous carriers of IGFALS gene mutations are frequently shorter than their wild-type relatives, suggesting that IGFALS haploinsufficiency could result in short stature. We have characterized IGFALS gene variants in idiopathic short stature (ISS) and in normal children, determining their impact on height and the IGF system.

PATIENTS AND METHODS

In 188 normal and 79 ISS children levels of IGF-1, IGFBP-3, ALS, ternary complex formation (TCF) and IGFALS gene sequence were determined.

RESULTS

In sum, 9 nonsynonymous or frameshift IGFALS variants (E35Gfs*17, G83S, L97F, R277H, P287L, A330D, R493H, A546V and R548W) were found in 10 ISS children and 6 variants (G170S, V239M, N276S, R277H, G506R and R548W) were found in 7 normal children. If ISS children were classified according to the ability for TCF enhanced by the addition of rhIGFBP-3 (TCF+), carriers of pathogenic IGFALS gene variants were shorter and presented lower levels of IGF-1, IGFBP-3 and ALS in comparison to carriers of benign variants. In ISS families, subjects carrying pathogenic variants were shorter and presented lower IGF-1, IGFBP-3 and ALS levels than noncarriers.

CONCLUSIONS

These findings suggest that heterozygous IGFALS gene variants could be responsible for short stature in a subset of ISS children with diminished levels of IGF-1, IGFBP-3 and ALS.

Study of primary IGF-1 deficiency in Egyptian children with idiopathic short stature

BACKGROUND/AIMS

Primary insulin-like growth factor-1 (IGF-1) deficiency (IGFD) is defined by low levels of IGF-1 without growth hormone (GH) deficiency and absence of secondary causes. The aim of this study was to evaluate IGF-1 in Egyptian children with idiopathic short stature (ISS) and describe patients with IGFD.

METHODS

This cross-sectional study included 50 children with ISS following up at the Diabetes Endocrine and Metabolism Pediatric Unit at Cairo University Pediatric Hospital. Children were included based on the following criteria: (1) short stature with current height standard deviation score (SDS) ≤-2.5; (2) age between 2 and 9 years in boys and 2 and 8 years in girls, and (3) prepubertal status. Exclusion criteria were: (1) identified cause of short stature and (2) pubertal children. IGF-1-deficient children were defined as children without GH deficiency and with IGF-1 levels below the 2.5th percentile.

RESULTS

Among 50 children with ISS, 14 (28%) patients had low IGF-1 levels, consistent with the diagnosis of primary IGFD. When compared with non-IGFD children, IGFD children had lower birth weight SDS (-1.8 vs. -0.7 SDS, p < 0.0001) and lower height SDS (-4.2 vs. -3.1 SDS, p < 0.05) and more delayed bone age (2.6 vs. 1.6 years, p = 0.001).

CONCLUSION

Primary IGF-1 deficiency is found in 28% of children with ISS.

Characterizing short stature by insulin-like growth factor axis status and genetic associations: results from the prospective, cross-sectional, epidemiogenetic EPIGROW study

CONTEXT

Serum IGF-I levels are often low in patients with short stature (SS) without defined etiology. Hence, genetic investigations have focused on the GH-IGF-I axis.

OBJECTIVE

Our objectives were to characterize IGF-I axis status and search for a broader range of genetic associations in children with SS and normal GH.

DESIGN AND SETTING

We conducted a prospective, cross-sectional, epidemiogenetic case-control study in 9 European countries (2008-2010).

PARTICIPANTS

Children (n = 275) aged ≥2 years with SS without defined etiology (≤-2.5 height SD score [SDS]) and ≥1 peak GH ≥7 μg/L) were recruited.

METHODS

Serum IGF-I, IGF-binding protein-3 (IGFBP-3), and acid-labile subunit (ALS) levels were measured in a central laboratory. Candidate gene exome sequencing was performed in this cohort and ethnicity-matched controls.

RESULTS

Serum IGF-I, IGFBP-3, and ALS levels were highly correlated, but there was a discrepancy between prevalence of IGF-I, IGFBP-3, and ALS deficiencies (53%, 30%, and 0.8%, respectively). An insertion-deletion (Indel) on the IGF1 gene (P = 1.2 × 10(-5), Bonferroni-corrected; case vs control frequency: 0.04 vs 0.112), an Indel on NFKB1 (P = 1.36 × 10(-10); case vs control frequency: 0.464 vs 0.272), and 2 single-nucleotide polymorphisms on ZBTB38 (P < 2.3 × 10(-6)) were associated with SS. At P < 10(-4), single-nucleotide polymorphisms on genes related to protein kinase regulation, MAPK, and Fanconi pathways were also associated with SS.

CONCLUSIONS

IGF-I deficiency is a common feature in SS without defined etiology; an Indel in the IGF1 gene was associated with SS. However, genes involved in transcriptional regulation (NFKB1 and ZBTB38) and growth factor signaling were also associated, providing further candidates for genetic investigations on individual patients.

Cognitive function in acromegaly: description and brain volumetric correlates

In acromegaly, we reported on increased rates of affective disorders such as dysthymia and depression, as well as structural brain changes. Objective of this study was to determine if cognitive impairments in patients with acromegaly exist and whether such impairments are associated with structural brain alterations defined by magnetic resonance imaging (MRI). In this cross-sectional study, 55 patients with biochemically confirmed acromegaly were enrolled. MRI data were compared with 87 control subjects. Main outcome measures were performance levels in 13 cognitive tests covering the domains of attention, memory and executive function, with performance below the cut-off level of the 16th percentile rated as impaired. In addition, individual global and hippocampal volume changes were defined for each patient in reference to a normative sample. We found that up to 33.3% of the patients were impaired in the attention, up to 24.1% in the memory, and up to 16.7% in the executive function domain. 67.3% of the patients failed to reach the cut-off level in at least one subtest. MRI demonstrated increased global, left and right hippocampal grey matter and white matter, particularly early in the disease course. Rather few positive than expected negative correlations could be established between the hippocampal grey matter gain and cognitive performance. Cognitive dysfunction, particularly attentional deficits, are common in acromegaly, rendering neuropsychological testing essential in the diagnostic work-up.

IGF-1 treatment reduces weight loss and improves outcome in a rat model of cancer cachexia

BACKGROUND: A hallmark symptom of cancer cachexia is the loss of skeletal muscle. This is at least partially due to a deregulation of the growth hormone/IGF-1 axis and a subsequently impaired protein synthesis in skeletal muscle. Here, we investigated the effect of IGF-1 supplementation in a rat model of cancer cachexia. METHODS: Juvenile rats were inoculated with the Yoshida AH-130 hepatoma and treated once daily with 0.3 mg kg(-1) day(-1) (low dose) or 3 mg kg(-1) day(-1) (high dose) IGF-1 or placebo for a period of maximal 16 days. Body weight and body composition (by NMR) were assessed at baseline and at the end of the study or day of death. Locomotor activity and food intake were assessed at baseline and day 10/11 after tumour inoculation for 24 h. RESULTS: Untreated tumour-bearing rats lost 55.3 ± 2.14 g body weight, which was reduced by low-dose to -39.6 ± 11.1 g (p = 0.0434) and high-dose IGF-1 to -42.7 ± 8.8 g (p = 0.057). Placebo-treated rats lost 41.4 ± 2.0-g lean mass, which was attenuated by low-dose IGF-1 (-28.8 ± 8.3 g, p = 0.041) and high-dose IGF-1 (-30.9 ± 7.4, p = 0.067). Spontaneous activity and food intake were improved by low-dose IGF-1 only. No effect on fat mass was observed. Low-dose IGF-1 significantly reduced mortality (HR = 0.45, 95%CI = 0.21-0.93, p = 0.0315), whilst the high dose did not reach significance (HR = 0.68, 95%CI = 0.26-1.74, p = 0.42). CONCLUSION: Low-dose IGF-1 reduced mortality and attenuated loss of body weight as well as muscle mass in the Yoshida hepatoma rat model. Moreover, an improved quality of life was observed in these animals. Further experiments using different doses are necessary.

Growth, final height and endocrine sequelae in a UK population of patients with Hurler syndrome (MPS1H)

OBJECTIVE

Hurler Syndrome, (MPSIH) is an inborn error of glycosaminoglycan metabolism. Haematopoietic stem cell transplantation (HSCT) has transformed the prognosis for these children. Prior to transplant patients receive chemotherapy or chemo-radiotherapy. Regular screening for the development of endocrine sequelae is therefore essential. We present for the first time data on final adult height and endocrine complications in children with MPSIH post HSCT.

DESIGN

Retrospective case note study and a prospective programme of growth and endocrine assessment.

PATIENTS

22 patients were included, mean age at last assessment 12.2 (Range 6.3-21.6) years. Mean age at HSCT was 1.3 (SD 0.6) years. Conditioning included mostly busulphan and cyclophosphamide, with 5 patients receiving total body irradiation prior to second transplant.

RESULTS

Height SDS decreased over time. Final height (FH) was attained in seven patients with male FH SDS -4.3 (Range -3.8, -5.1) and female FH SDS -3.4 (Range -2.9, -5.6). Eight of 13 patients tested had evidence of high growth hormone (GH) levels, while one had GH deficiency. Adrenal and thyroid function was normal in all. 11 patients were pubertal or post pubertal. Two females had pubertal failure requiring intervention. All male patients had spontaneous, complete puberty; however three patients have reduced testicular volumes. Five out of 13 patients tested had an abnormal oral glucose tolerance test.

CONCLUSION

Growth is impaired, primarily related to skeletal dysplasia, but also associated with GH resistance. Pubertal development may be compromised and abnormalities of glucose metabolism are common. We recommend a structured endocrine surveillance programme for these patients.

Epigenetics of programmed obesity: alteration in IUGR rat hepatic IGF1 mRNA expression and histone structure in rapid vs. delayed postnatal catch-up growth

Maternal food restriction (FR) during pregnancy results in intrauterine growth-restricted (IUGR) offspring that show rapid catch-up growth and develop metabolic syndrome and adult obesity. However, continued nutrient restriction during nursing delays catch-up growth and prevents development of obesity. Epigenetic regulation of IGF1, which modulates growth and is synthesized and secreted by the liver, may play a role in the development of these morbidities. Control (AdLib) pregnant rats received ad libitum food through gestation and lactation, and FR dams were exposed to 50% food restriction from days 10 to 21. FR pups were nursed by either ad libitum-fed control dams (FR/AdLib) or FR dams (FR/FR). All pups were weaned to ad libitum feed. Maternal FR resulted in IUGR newborns with significantly lower liver weight and, with the use of chromatin immunoprecipitation, decreased dimethylation at H3K4 in the IGF1 region was observed. Obese adult FR/AdLib males had decreased dimethylation and increased trimethylation of H3K4 in the IGF1 region. This corresponded to an increase in mRNA expression of IGF1-A (134 ± 5%), IGF1-B (165 ± 6%), IGF1 exon 1 (149 ± 6%), and IGF1 exon 2 (146 ± 7%) in the FR/AdLib compared with the AdLib/AdLib control group. In contrast, nonobese FR/FR had significantly higher IGF1-B mRNA levels (147 ± 19%) than controls with no difference in IGF1-A, exon 1 or exon 2. Modulation of the rate of IUGR newborn catch-up growth may thus protect against IGF1 epigenetic modifications and, consequently, obesity and associated metabolic abnormalities.

Recombinant human insulin-like growth factor-1 treatment: ready for primetime

The combination of targeted gene knockout studies in animals and human mutational analysis has demonstrated the key role of the IGF system in mammalian growth, both in utero and postnatally. The concept of IGF deficiency as a diagnostic category for children with growth failure first was proposed in the mid 1990s, and has gained support through the demonstration of patients with mutations in key components of the growth hormone (GH)-IGF axis, as well as the widespread use of IGF-I assays for evaluating short stature. The US Food and Drug Administration has approved IGF-I therapy for treating children who have severe primary IGF deficiency, defined as a height SD score < or =-3 and a serum IGF-1 SD score < or =-3, normal serum GH. Recent studies have demonstrated the efficacy and safety of IGF-I therapy in such patients, and investigations are in progress to determine optimal dosing. The availability of IGF-I therapy thus has expanded the therapeutic tool chest available to endocrinologists caring for children who have growth failure.

Peptide hormones as developmental growth and differentiation factors

Peptide hormones, usually considered to be endocrine factors responsible for communication between tissues remotely located from each other, are increasingly being found to be synthesized in developing tissues, where they act locally. Several hormones are now known to be produced in developing tissues that are unrelated to the endocrine gland of origin in the adult. These hormones are synthesized locally, and are active as differentiation and survival factors, before the developing adult endocrine tissue becomes functional. There is increasing evidence for paracrine and/or autocrine actions for these factors during development, thus, placing them among the conventional growth and differentiation factors. We review the evidence for the view that thyroid hormones, growth hormone, prolactin, insulin, and parathyroid hormone-related protein are developmental growth and differentiation factors.

Idiopathic short stature: definition, epidemiology, and diagnostic evaluation

Idiopathic short stature is a condition in which the height of the individual is more than 2 SD below the corresponding mean height for a given age, sex and population, in whom no identifiable disorder is present. It can be subcategorized into familial and non-familial ISS, and according to pubertal delay. It should be differentiated from dysmorphic syndromes, skeletal dysplasias, short stature secondary to a small birth size (small for gestational age, SGA), and systemic and endocrine diseases. ISS is the diagnostic group that remains after excluding known conditions in short children.

Insulin-like growth factor-I (rhIGF-I) therapy of short stature

The United States Food and Drug Administration (FDA) approved the use of subcutaneously injected rhIGF-I in late 2005 for treatment of children with severe short stature from growth hormone (GH) insensitivity due to genetic defects in the GH receptor or postreceptor mechanisms or from the development of GH inactivating antibodies. The approval was based on 15 years experience treating these rare conditions with rhIGF-I. Because of the very small numbers of children with these conditions, there has been an effort to justify and promote broader use for rhIGF-I. Attempts to identify GH unresponsiveness in children with idiopathic short stature (ISS) have yielded only a handful of patients with rare genetic disorders. IGF-I treatment for unequivocal GH insensitivity improves but does not correct growth failure, in contrast to the typical experience with GH replacement of GH deficiency. This emphasizes the importance of direct effects of GH at the growth plate, including the stimulation of maturation of cartilage precursor cells and local production of IGF-I, effects that cannot be duplicated by exogenous administration of rhIGF-I. Adverse effects testify to the more than adequate delivery of administered rhIGF-I to other tissues; these include lymphoid hyperplasia, coarsening of the facies, and increased percentage body fat. The absence of convincing evidence of GH insensitivity in a substantial number of children with ISS, the limited ability of endocrine IGF-I to restore normal growth in those with unequivocal GH unresponsiveness, the suppression of endogenous GH (and thereby, local GH effects on growth) that occurs with IGF-I administration, the risk profile, and the absence of data on efficacy in other than proven severe GH insensitivity, led the Drug and Therapeutics Committee of the Lawson Wilkins Pediatric Endocrine Society to conclude that rhIGF-I use is only justified in conditions approved by the FDA and that other growth promotional use should only be investigational. Nonetheless, substantial numbers of children are being treated with rhIGF-I off-label, exuberant estimates of potentially eligible patients are projected, and several uncontrolled clinical trials have been undertaken which are not based on sound preliminary data or established growth principles, and a single four-arm study begun comparing monotherapy with rhGH to combination rhGH with three dosages of rhIGF-I as a single daily injection, a means of administration of rhIGF-I that has not been tested.

Parafibromin, a component of the human PAF complex, regulates growth factors and is required for embryonic development and survival in adult mice

Parafibromin, a transcription factor associated with the PAF complex, is encoded by the HRPT2 gene, mutations of which cause the hyperparathyroidism-jaw tumor syndrome (OMIM145001). To elucidate the function of parafibromin, we generated conventional and conditional Hrpt2 knockout mice and found that Hrpt2(-/-) mice were embryonic lethal by embryonic day 6.5 (E6.5). Controlled deletion of Hrpt2 after E8.5 resulted in apoptosis and growth retardation. Deletion of Hrpt2 in adult mice led to severe cachexia and death within 20 days. To explore the mechanism underlying the embryonic lethality and death of adult mice, mouse embryonic fibroblasts (MEFs) were cultured and Hrpt2 was deleted in vitro. Hrpt2(-/-) MEFs underwent apoptosis, while Hrpt2(+/+) and Hrpt2(+/-) MEFs grew normally. To study the mechanism of this apoptosis, Hrpt2(+/+) and Hrpt2(-/-) MEFs were used in cDNA microarray, semiquantitative reverse transcription-PCR, and chromatin immunoprecipitation assays to identify genes regulated by parafibromin. These revealed that Hrpt2 expression and the parafibromin/PAF complex directly regulate genes involved in cell growth and survival, including H19, Igf1, Igf2, Igfbp4, Hmga1, Hmga2, and Hmgcs2. Thus, our results show that expression of Hrpt2 and parafibromin is pivotal in mammalian development and survival in adults and that these functions are likely mediated by the transcriptional regulation of growth factors.

Growth hormone signalling: sprouting links between pathways, human genetics and therapeutic options

Our molecular understanding of growth hormone-induced signal transduction has improved significantly over the past decades. At the same time, human population genetics and the analysis of genetically engineered animals have led to the discovery of genes that control specific aspects of the overall growth process. Although, currently, growth disorders are still diagnosed and treated on empirical bases, it might soon be possible to stratify patients predominantly by genetic defect, with treatment based on our molecular understanding of the role of the affected gene in the disease.

Developmental origins of life history: Growth, productivity, and reproduction

There is now much evidence that early life undernutrition elevates risk of diseases like cardiovascular disease. Less clear is whether the underlying developmental plasticity in metabolism and physiology evolved to serve an adaptive function, beyond these effects on pathophysiology. This review builds from principles of life history theory to propose a functional model linking early environments with adult biology. An organism has metabolic potential in excess of survival requirements, called productivity, that supports growth before being shunted into reproduction after growth ceases. This concept from inter-specific studies leads to the prediction that plasticity in growth rate will be positively correlated with components of future adult reproductive expenditure. Consistent with this idea, evidence is reviewed that early nutrition or growth rate predict offspring size in females, and increased somatic investment related to reproductive strategy in males. Thus, population birth weight and sexual size dimorphism are predicted to increase in response to improvements in early nutrition. A striking feature of the continuity of metabolic production is its perpetuation not merely during the lifecycle but across generations: in females, growth rate predicts future nutritional investment in reproduction, which in turn determines fetal growth rate in the next generation. Growth and reproduction serve as mutually-defining templates, thus creating a phenotypic bridge allowing ecologic information to be maintained during ontogeny and transmitted to offspring. Resetting of metabolic production in response to maternal nutritional cues may serve a broader goal of integrating nutritional information within the matriline, thus providing a more reliable basis for adjusting long-term strategy.

Controversy in clinical endocrinology: problems with reclassification of insulin-like growth factor I production and action disorders

CONTEXT

Recent developments in the IGF field have raised questions on whether this is the right time to redefine IGF deficiency.

OBJECTIVE

In this controversy, arguments are made against the need for redefining IGF deficiency at this moment, suggesting instead to wait for further clinical developments.

CASE

Although a number of rare case reports of IGF deficiency with precise molecular etiologies have been described, the vast majority of the cases remain clinically defined and without a genetic diagnosis.

INTERVENTIONS

Because IGF products are now available for clinical use in IGF-deficient patients, we are still using GH stimulation and static IGF levels as our only clinical diagnostic and classification tools. POSITIONS: We need to develop additional clinical tools, side by side with molecular tools, for the diagnosis and subclassification of IGF deficiency. Chief among these are the IGF-generation test for identification of GH-insensitive patients and genetic panels of polymorphic changes in relevant genes.

CONCLUSIONS

Until further progress is made in the clinical classification of IGF deficiency, we should not change the current classification, and, when we do, it should be the responsibility of the relevant societies in the field to conduct a consensus statement on the topic first.