Urinary GH and IGF-I excretion in nine year-old children: relation to sex, current size and size at birth

Tracking of Serum DHEAS Concentrations from Age 1 to 6 Years: A Prospective Cohort Study

Context

Adrenarche is a gradual process, but its programming is unknown.

Objective

The objective of this article is to examine the trajectory of dehydroepiandrosterone sulfate (DHEAS) from age 1 to 6 years and the associations of early growth with DHEAS concentration by age 6 years.

Design and participants

Longitudinal data from a population sample of 78 children (43 girls) with serum samples for DHEAS and insulin-like growth factor 1 (IGF-1) measurements available at ages 1 and 6 years.

Main outcome measure

Serum DHEAS concentration at age 6 years.

Results

DHEAS concentration at age 1 year correlated with DHEAS concentration at age 6 years (r = 0.594, P < .001). DHEAS levels at age 6 years increased with tertiles of DHEAS at age 1 year (medians (µg/dL); 4.2, 14.4, 22.6; P < .001) and with those of greater increase in length by age 1 year (6.0, 11.7, 16.4; P = .047), and decreased with tertiles of birth length (17.7, 13.3, 7.1; P = .042). In a regression model including birth size, biochemical covariates at age 1 year, and growth measures by age 6 years, higher DHEAS concentration at age 1 year was an independent determinant of falling into the highest DHEAS tertile at age 6 years.

Conclusions

Higher serum DHEAS concentrations already at age 1 year are associated with those at age 6 years. Also, shorter birth length and rapid catch-up growth in length by age 1 year are associated with higher DHEAS concentrations at age 6 years. These results corroborate the early origin of adrenarche and strongly suggest that part of adrenarchal programming already takes place by the end of infancy.

A critical review of the role of milk and other dairy products in the development of obesity in children and adolescents

Existing reviews suggest that milk and other dairy products do not play a role in the development of obesity in childhood, but they do make an important contribution to children's nutrient intake. It is thus curious that public health advice on the consumption of dairy products for children is often perceived as unclear. The present review aimed to provide an overview of the totality of the evidence on the association between milk and other dairy products, and obesity and indicators of adiposity, in children. Our search identified forty-three cross-sectional studies, thirty-one longitudinal cohort studies and twenty randomised controlled trials. We found that milk and other dairy products are consistently found to be not associated, or inversely associated, with obesity and indicators of adiposity in children. Adjustment for energy intake tended to change inverse associations to neutral. Also, we found little evidence to suggest that the relationship varied by type of milk or dairy product, or age of the children, although there was a dearth of evidence for young children. Only nine of the ninety-four studies found a positive association between milk and other dairy products and body fatness. There may be some plausible mechanisms underlying the effect of milk and other dairy products on adiposity that influence energy and fat balance, possibly through fat absorption, appetite or metabolic activity of gut microbiota. In conclusion, there is little evidence to support a concern to limit the consumption of milk and other dairy products for children on the grounds that they may promote obesity.

A Longitudinal Study of Income Differences in the Height-BMI Relation among U.S. Children Ages 6 to 14

Previous work has shown a positive height-obesity association in U.S. children that is more pronounced in those from lower-income families than in those from higher-income families. That work has been limited to cross-sectional analysis. This study evaluates income differentials in the inter-temporal associations between childhood height and obesity in U.S. children ages 6 to 14. Pooled samples of 9,670 female and 10,110 male children from the U.S. Early Childhood Longitudinal Study-Kindergarten Cohort (ECLS-K) were evaluated in multilevel mixed effects models. The results indicated a modest height-income interaction such that the concurrent height-obesity association was weaker at higher incomes. This strengthened into adolescence for females and weakened for males. With respect to height growth, for lower-income males, being shorter before the typical start of the growth spurt (≈ 9 years) and experiencing faster later growth (between 11 and 14 years) were attributes less strongly associated with subsequent obesity. There were no indicated income interactions with height growth in females.

Growth hormone doping in sports: a critical review of use and detection strategies

GH is believed to be widely employed in sports as a performance-enhancing substance. Its use in athletic competition is banned by the World Anti-Doping Agency, and athletes are required to submit to testing for GH exposure. Detection of GH doping is challenging for several reasons including identity/similarity of exogenous to endogenous GH, short half-life, complex and fluctuating secretory dynamics of GH, and a very low urinary excretion rate. The detection test currently in use (GH isoform test) exploits the difference between recombinant GH (pure 22K-GH) and the heterogeneous nature of endogenous GH (several isoforms). Its main limitation is the short window of opportunity for detection (~12-24 h after the last GH dose). A second test to be implemented soon (the biomarker test) is based on stimulation of IGF-I and collagen III synthesis by GH. It has a longer window of opportunity (1-2 wk) but is less specific and presents a variety of technical challenges. GH doping in a larger sense also includes doping with GH secretagogues and IGF-I and its analogs. The scientific evidence for the ergogenicity of GH is weak, a fact that is not widely appreciated in athletic circles or by the general public. Also insufficiently appreciated is the risk of serious health consequences associated with high-dose, prolonged GH use. This review discusses the GH biology relevant to GH doping; the virtues and limitations of detection tests in blood, urine, and saliva; secretagogue efficacy; IGF-I doping; and information about the effectiveness of GH as a performance-enhancing agent.

Body size in early life and adult levels of insulin-like growth factor 1 and insulin-like growth factor binding protein 3

Body size in early life has been associated with breast cancer risk. This may be partly mediated through the insulin-like growth factor (IGF) pathway. The authors assessed whether birth weight, body fatness at ages 5 and 10 years, and body mass index (BMI; weight (kg)/height (m)(2)) at age 18 years were associated with plasma concentrations of insulin-like growth factor 1 (IGF-1) and insulin-like growth factor binding protein 3 in 6,520 women aged 32-70 years at blood draw from the Nurses' Health Study (1990-2006) and Nurses' Health Study II (1997-2005). Birth weight, body fatness in childhood, and BMI at age 18 years were inversely associated with adult IGF-1 levels. For example, IGF-1 levels were 11.9% lower in women who reported being heaviest at age 10 years than in those who were leanest at age 10 (P-trend < 0.0001). Further, women who reported their birth weight as ≥10 pounds (≥4.5 kg) (vs. <5.5 pounds (<2.5 kg)) had 7.9% lower IGF-1 levels (P-trend = 0.002). Women whose BMI at age 18 years was ≥30 (vs. <20) had 14.1% lower IGF-1 levels (P-trend < 0.0001). Similar inverse associations were observed for insulin-like growth factor binding protein 3. These observations did not vary by adult BMI or menopausal status at blood draw. These findings suggest that altered IGF-1 levels in adulthood may be a mechanism through which early-life body size influences subsequent breast cancer risk.

The role of neurotrophic factors in autism

Autism spectrum disorders (ASDs) are pervasive developmental disorders that frequently involve a triad of deficits in social skills, communication and language. For the underlying neurobiology of these symptoms, disturbances in neuronal development and synaptic plasticity have been discussed. The physiological development, regulation and survival of specific neuronal populations shaping neuronal plasticity require the so-called 'neurotrophic factors' (NTFs). These regulate cellular proliferation, migration, differentiation and integrity, which are also affected in ASD. Therefore, NTFs have gained increasing attention in ASD research. This review provides an overview and explores the key role of NTFs in the aetiology of ASD. We have also included evidence derived from neurochemical investigations, gene association studies and animal models. By focussing on the role of NTFs in ASD, we intend to further elucidate the puzzling aetiology of these conditions.

Milk intake and total dairy consumption: associations with early menarche in NHANES 1999-2004

BACKGROUND

Several components of dairy products have been linked to earlier menarche.

METHODS/FINDINGS

This study assessed whether positive associations exist between childhood milk consumption and age at menarche or the likelihood of early menarche (<12 yrs) in a U.S sample. Data derive from the National Health and Nutrition Examination Survey (NHANES) 1999-2004. Two samples were utilized: 2657 women age 20-49 yrs and 1008 girls age 9-12 yrs. In regression analysis, a weak negative relationship was found between frequency of milk consumption at 5-12 yrs and age at menarche (daily milk intake β = -0.32, P<0.10; "sometimes/variable milk intake" β = -0.38, P<0.06, each compared to intake rarely/never). Cox regression yielded no greater risk of early menarche among those who drank milk "sometimes/varied" or daily vs. never/rarely (HR: 1.20, P<0.42, HR: 1.25, P<0.23, respectively). Among the 9-12 yr olds, Cox regression indicated that neither total dairy kcal, calcium and protein, nor daily milk intake in the past 30 days contributed to early menarche. Girls in the middle tertile of milk intake had a marginally lower risk of early menarche than those in the highest tertile (HR: 0.6, P<0.06). Those in the lowest tertiles of dairy fat intake had a greater risk of early menarche than those in the highest (HR: 1.5, P<0.05, HR: 1.6, P<0.07, lowest and middle tertile, respectively), while those with the lowest calcium intake had a lower risk of early menarche (HR: 0.6, P<0.05) than those in the highest tertile. These relationships remained after adjusting for overweight or overweight and height percentile; both increased the risk of earlier menarche. Blacks were more likely than Whites to reach menarche early (HR: 1.7, P<0.03), but not after controlling for overweight.

CONCLUSIONS

There is some evidence that greater milk intake is associated with an increased risk of early menarche, or a lower age at menarche.

Dairy and milk consumption and child growth: Is BMI involved? An analysis of NHANES 1999-2004

Humans are unique among mammals in that many consume cow's milk or other dairy products well beyond the traditional age of weaning. Milk provides various nutrients and bioactive molecules to support growth and development, and the question arises as to whether this dietary behavior influences growth parameters. There is evidence that milk makes positive contributions to growth in height, but its associations with other aspects of body size, such as body mass index (BMI), are not well-established. National Health and Nutrition Examination Survey (NHANES) data from 1999 to 2004 and multivariate regression analysis were used to test the hypothesis that milk (g) or total dairy product consumption (kJ) is associated with higher BMI percentile among US White, Black, and Mexican-American children of age 2-4 years (n = 1,493) and 5-10 years (n = 2,526). Younger children in the highest quartile of dairy intake had higher BMIs (beta = 7.5-8.0; P < 0.01) than those in the lowest two quartiles. Controlling for energy intake eliminated differences between QIV and QI. Among children of 5-10 years of age dairy intake had no relationship to BMI. Young children in the highest quartile of milk intake had higher BMIs than all lower quartiles (beta = 7.1-12.8; beta = 6.3-11.8 in energy-controlled models; P < 0.05). Among children of 5-10 years of age, those in QIV for milk intake had higher BMIs than those in QII (beta = 8.3; beta = 7.1 in energy-controlled model; P < 0.01). Controlling for total protein or calcium did not change the results. Milk had more consistent positive associations with BMI than did dairy products, and these were strongest among children of 2-4 years of age.

Through the Looking Glass at Early-Life Exposures and Breast Cancer Risk

The global increase in the proportion of women diagnosed with breast cancer, inadequate access to screening and high cost of treatment for breast cancer argue strongly for a greater focus on preventive strategies. But at what age is it appropriate to begin targeting preventive approaches? The recognized role of perinatal nutrition in neurologic development and the relation of maternal nutritional status to birthweight and subsequent risk of hypertension, diabetes, and cardiovascular disease identify pregnancy and early childhood as potential phases for prevention. This review examines indicators of hormonal and nutritional exposures in early life and breast cancer risk through the lens of the life course paradigm integrated with maternal and child health research and methodology. Compared to women who were normal birthweight (2500-3999 g), women who weighed>or=4,000 g at birth have a 20 percent to 5-fold increased risk of premenopausal breast cancer. Women born preterm and likely to be small- or large-for-date also have an increased risk. Birth length is directly associated with risk and has a larger magnitude of effect than birthweight. Prior preeclamptics and their daughters have a lower risk of breast cancer than comparable normotensives. An association between infant feeding practices and breast cancer is unclear without improved exposure assessment and analysis. Rapid childhood and pubertal linear growth increases breast cancer risk, while greater body fat over the same periods reduces risk. Growth data thus far have not been calculated in Z-scores from reference growth curves for comparison across studies. Events and secular trends influencing birth cohorts may not be adequately addressed, thereby limiting the interpretation and implications of the findings. Research in nonhuman primates may help uncover underlying mechanisms.

The impact of birth weight on prostate cancer incidence and mortality in a population-based study of men born in 1913 and followed up from 50 to 85 years of age

BACKGROUND

Insulin-like growth factor-I (IGF-I) hormone is directly associated with birth weight (BW), and high IGF-I measured in adults is associated with increased risk of prostate cancer (PCA). Whether BW and PCA are related is inconclusive to date.

METHODS

BW and PCA incidence and mortality data for a population-based cohort of 1,436 singleton Swedish men born in 1913 and followed until 85 years of age were obtained.

RESULTS

BW > or = 4,250 g was associated with significantly higher PCA incidence [62% (CI: 4%-151%)] and PCA mortality [82% (CI: 3%-221%)] than BW 3,001-4,249 g, even when other potential effect modifiers were taken into account. The hazards ratio for PCA incidence fell from approximately 3 at age 50 to unity at age 85. Approximately one out of every six PCA incident cases between 50 and 70 years of age could be attributed to BW > or = 4,250 g.

CONCLUSIONS

In the current study PCA incidence and mortality rate appears to increase with BW.

Lower Birth Weight Associated with Current Overweight Status Is Related with the Metabolic Syndrome in Obese Japanese Children

The purpose of this study was to clarify the relationship between lower birth weight and current overweight status and to examine the involvement of these factors in the development of the metabolic syndrome (MS) in obese Japanese children. We examined 97 obese boys (mean age 11.3 years; mean percentage overweight [POW] 52.4%) and 29 obese girls (mean age 11.1 years; mean POW 58.3%). The anthropometric measurements, blood pressure, fasting serum insulin and blood glucose, liver enzymes, lipids and lipoproteins were measured. Birth weight and gestational weeks were also recorded. The subjects were divided into either an MS group or a Non-MS group using criteria proposed for Japanese children. We compared the weight parameters (birth weight, current weight and current weight-to-birth weight ratio [WBWR]) between the two groups and analyzed the relationships between the weight parameters and metabolic derangements. There were no significant differences in age or anthropometric measurements between the two groups. However, birth weight in the MS group was lower than that in the Non-MS group, while WBWR of the MS group was higher than that in the Non-MS group. Blood pressure and serum insulin correlated positively with WBWR. These findings suggested that lower birth weight with current overweight status was associated with the MS in obese Japanese children. We were unable to clarify whether subjects with lower birth weight who achieved proper weight gains had the same risk as subjects with appropriate birth weight. However, they should be assisted to grow adequately to prevent future metabolic derangements.

Cow's milk and linear growth in industrialized and developing countries

The strongest evidence that cow's milk stimulates linear growth comes from observational and intervention studies in developing countries that show considerable effects. Additionally, many observational studies from well-nourished populations also show an association between milk intake and growth. These results suggest that milk has a growth-stimulating effect even in situations where the nutrient intake is adequate. This effect is supported by studies that show milk intake stimulates circulating insulin-like growth factor (IGF)-I, which suggests that at least part of the growth-stimulating effects of milk occur through the stimulation of IGFs. Given that the biological purpose of milk is to support the newborn during a period of high growth velocity, such an effect seems plausible. Adding cow's milk to the diet of stunted children is likely to improve linear growth and thereby reduce morbidity. In well-nourished children, the long-term consequences of an increased consumption of cow's milk, which may lead to higher levels of IGF-I in circulation or an increase in the velocity of linear growth, are likely to be both positive and negative. Based on emerging data that suggest both growth and diet during early life program the IGF axis, the association between milk intake and later health is likely to be complex.

Associations of adiposity from childhood into adulthood with insulin resistance and the insulin-like growth factor system: 65-year follow-up of the Boyd Orr Cohort

CONTEXT

One metabolic pathway through which adiposity influences disease risk may be via alterations in insulin and IGF metabolism.

OBJECTIVE

Our objective was to investigate associations of adiposity at different stages of life with insulin and the IGF system.

DESIGN, SETTING, AND PARTICIPANTS

The study was a 65-yr follow-up of 728 Boyd Orr cohort participants (mean age, 71 yr) originally surveyed between 1937 and 1939.

MAIN OUTCOMES

Outcomes included homeostasis model assessment of insulin resistance, total IGF-I and IGF-II, IGF binding protein (IGFBP)-2, and IGFBP-3 in adulthood.

RESULTS

Childhood body mass index (BMI) was weakly inversely related to adult IGF-I (coefficient per BMI sd, -3.4 ng/ml; 95% confidence interval, -7.3 to 0.5; P = 0.09). IGF-II (but not IGF-I) increased with higher current fat mass index (coefficient, 26.1 ng/ml; 95% confidence interval, 4.6 to 47.6; P = 0.02) and waist-hip ratio (30.0 ng/ml; 9.4 to 50.5; P = 0.004). IGFBP-2 decreased by 21.2% (17.2 to 24.9; P < 0.001), and homeostasis model assessment of insulin resistance increased by 38.8% (28.9 to 49.6; P < 0.001) per sd higher adult BMI. Among thin adults (BMI tertiles 1 and 2), IGFBP-2 was positively, and insulin resistance was inversely, associated with childhood BMI.

CONCLUSION

There was only weak evidence that associations of childhood BMI with chronic disease risk may be mediated by adult IGF-I levels. Circulating IGFBP-2 in adulthood, a marker for insulin sensitivity, was inversely associated with current adiposity, but overweight children who became relatively lean adults were more insulin sensitive than thinner children. The findings may indicate programming of later insulin sensitivity and consequently IGFBP-2 levels in response to childhood adiposity. The role of IGF-II in obesity-related chronic diseases warrants additional investigation.

Timing of puberty determines serum insulin-like growth factor-I in late adulthood

CONTEXT

IGFs may play an important role in disease etiology, especially cancer. Changes in diet can alter acute levels, but little is known about life course influences on IGF levels.

OBJECTIVE

The objective of the study was to examine the association between timing of puberty and adulthood serum IGFs (IGF-I and IGF binding protein-3).

DESIGN

This was a retrospective cohort study.

SETTING

Male pupils who attended a single school in Southern England were part of the study.

PARTICIPANTS

Participants in the study were a cohort of 1028 men born between 1927 and 1956 with anthropometric measures between 9 and 18 yr and adulthood serum IGF levels.

MAIN OUTCOME MEASURE

The study measured serum IGF-I and IGF binding protein-3 at mean age 63 yr.

RESULTS

Age at peak height velocity (APHV) was inversely associated with adult IGF-I levels. IGF-I decreased by 3.7 ng/ml (95% confidence interval 1.0-6.4, P = 0.007) for each sd increase in APHV. Prepubertal childhood height and body mass index were both inversely associated with APHV (P trend < 0.001). APHV was positively associated with adult height and inversely associated with adult body mass index. Adjustment for childhood, adult anthropometry, and other lifestyle factors did not substantially alter the association between APHV and adult IGF-I.

CONCLUSIONS

This is the first study to document an association between timing of puberty and adult IGF-I levels. A better understanding of life course determinants of the IGF system may provide new insights into disease etiology and primary prevention.

Insulin-like growth factor-I and growth in height, leg length, and trunk length between ages 5 and 10 years

OBJECTIVE

IGF-I, a major regulator of childhood growth, is also associated with the risk of several cancers in adult life. Adult height and particularly leg length are also associated with cancer risk. Prepubertal growth is more in leg than trunk length, and it has been suggested that leg length might be a biomarker of childhood IGF-I. However, there is little information on the association between childhood IGF-I and subsequent leg and trunk growth. In this study, we investigated the association of IGF-I measured at 5 and 7-8 yr with growth in height and the components of height (leg and trunk length) from 5 yr to 9-10 yr.

PARTICIPANTS

A total of 675 children participated in the Avon Longitudinal Study of Parents and Children.

RESULTS

IGF-I was strongly positively associated with growth in height in both sexes. Among boys, IGF-I was strongly associated with subsequent growth in both leg and trunk length, but there was no evidence that IGF-I was more strongly associated with one component of growth than the other. Among girls, IGF-I was strongly positively associated with growth in trunk but not leg length, although there was only weak evidence that these two associations differed in strength (P = 0.058).

CONCLUSIONS

These results support the contention that the associations between height and cancer may be mediated by variation in childhood IGF-I. However, they provide no evidence to support the hypothesis that leg length is a better biomarker of childhood IGF-I levels than trunk length.

Associations of childhood and adulthood height and the components of height with insulin-like growth factor levels in adulthood: a 65-year follow-up of the Boyd Orr cohort

CONTEXT

Taller individuals with longer legs have a higher risk of cancer but a lower risk of coronary heart disease.

OBJECTIVE

We investigated whether childhood height and its components are associated with the IGF system in adulthood.

DESIGN AND PARTICIPANTS

We analyzed data from 429 participants of the Boyd Orr cohort, for whom height measured in childhood (mean age, 7.4 yr) in 1937-1939 could be related to levels of IGF-I, IGF-II, IGF binding protein (IGFBP)-2, and IGFBP-3 in adulthood (mean age, 71.1 yr). In 385 participants, measured height in adulthood could be related to IGF levels.

RESULTS

In fully adjusted models (controlling for age, sex, socioeconomic factors, lifestyle, and body mass index), childhood height and its components were not associated with adult circulating IGF-I, IGF-II, or IGFBP-2 levels. IGFBP-3 was 85.5 ng/ml higher (95% confidence interval, -11.6 to 182.5; P = 0.08) per sd increase in childhood trunk length and 83.6 ng/ml lower (95% confidence interval, -10.3 to 177.5; P = 0.08) per sd increase in childhood leg/trunk ratio. Height in adulthood was not associated with IGF-I, IGF-II, or IGFBP-3 and was inversely associated with IGFBP-2 (P = 0.05) after additionally controlling for childhood height.

CONCLUSION

There was no evidence that associations of childhood height with cancer and coronary heart disease risk are mediated by IGF-I in adulthood. The anthropometric associations with IGFBP-2 and IGFBP-3 could be chance findings but warrant additional investigation. IGF levels in childhood may be more important determinants of long-term disease risk than adult levels.

Does milk make children grow? Relationships between milk consumption and height in NHANES 1999-2002

In the United States, milk (usually cow's milk) is widely considered an "essential food" to support bone growth among post-weaning age children, as evident in government-sponsored nutrition policies that mandate milk for children. Milk contains calories, protein, and calcium, among other nutrients, and bioactive components such as insulin-like growth factor-I (IGF-I), all of which may facilitate bone growth. There is a large literature on milk and/or calcium intake and its effects on bone density, but one aspect of bone mass--height--is not well studied in relation to milk consumption. Limited experimental studies show no consistent relationship across populations. To investigate this linkage among American children, analysis of the NHANES 1999-2002 was undertaken. NHANES data allow two hypotheses to be tested: (1) reported frequency of childhood milk consumption will be positively related to adult height and (2) height of children 5-18 years will be predicted by the reported frequency of milk consumption and/or milk intake from a 24-h dietary recall. Results indicate that adult height was positively associated with milk consumption at ages 5-12 and 13-17, after controlling for sex, education, and ethnicity. Among contemporary children, milk consumption had no effect on the height of 5-11 year olds after controlling for age, birthweight, energy intake, and ethnicity. In contrast, milk consumption frequency and milk intake (measured as grams of milk, or protein or calcium from milk) were significant predictors of the height of 12-18 year olds, along with age, sex, household income, and ethnicity. The greatest ethnic contrasts were between Mexican Americans and non-Hispanic whites and blacks, and milk variables remained significant predictors of height in these comparisons. Thus NHANES data show substantial variability in the effects of milk consumption on height.

Urinary insulin-like growth factor-I measurement in an actual sport competition, an additional approach in laboratory antidoping tests

BACKGROUND

The insulin-like growth factor hormone (IGF-I) is an important protein hormone under investigation with physical exercise and for doping detection. Urinary IGF-I level in fact represents a relevant measurement when the postexercise proteinuria is under analysis. To verify the IGF-I level variation in the circulation and in urinary excretion in the occasion of a competition, the plasma and urine IGF-I in athletes before and after an actual competitive event were measured.

METHODS

Twenty well-trained cyclists took part in a competition (102 km) and concluded the intense physical exercise in approximately 2(1/2) h. Urine and blood samples were collected from each athlete 10-20 min before and at the end of the competition. Plasma and urine total IGF-I (pIGF, uIGF), total urinary proteins (uPr), and creatinine (uCr) concentrations were measured.

RESULTS

The uIGF [from 76.2+/-15.8 to 256.9+/-29.1 ng/l (p<0.001)], uPr [from 29.4+/-6.7 to 325.9+/-95.1 mg/l (p<0.005)], and uCr [from 6.3+/-1.0 to 10.0+/-0.8 mmol/l (p<0.005)] significantly increased. The pIGF was 262.6+/-14.3 and 247.3+/-11.8 microg/l before and end-exercise, respectively. A statistical correlation between uIGF and uPr was demonstrated (p<0.001). The pIGF/uIGF ratio was significantly (p<0.05) decreased comparing the end with before the competition.

CONCLUSIONS

The pIGF/uIGF significantly decreased at the end, compared with before the competition, suggesting a changed uIGF excretion. This increment appeared to be increased, although not significantly, considering the ratio with uCr.

An investigation of fetal, postnatal and childhood growth with insulin-like growth factor I and binding protein 3 in adulthood

OBJECTIVE

Weight at birth and adult height are positively associated with cancer risk. These patterns may be mediated by the insulin-like growth factor (IGF) axis. We have examined whether pre- and postnatal growth patterns have a long-term influence on adult IGF-I and IGFBP-3 levels.

DESIGN

A follow-up study of a randomized controlled trial of milk supplementation in pregnancy and childhood.

SUBJECTS

A total of 951 individuals took part in a study of diet and growth in South Wales between 1972 and 1974 followed up from birth until their mid-20s.

MEASUREMENTS

Anthopometric measures at birth, postnatally up to 5 years of age and in adulthood, and serum measures of IGF-I and IGF-I to IGFBP-3 ratio at mean age of 25 years.

RESULTS

A total of 63 subjects (70%) provided blood for analysis. We found no association between birth dimensions and adult IGF-I. Subjects who exhibited 'catch-down growth' had lower IGF-I levels (P-value for trend 0.02). Adult height was positively related to IGF-I, for every one standard deviation increase in adult height, IGF-I increased by 3.75 ng/dl (95% CI 0.46-7.08, P = 0.03). Adiposity was inversely associated with the IGF-I and IGF-I to IGFBP-3 ratio and positively associated with IGFBP-3. The strength of the associations increased with age. Downward centile crossing at any time in childhood was associated with lower IGF-I whilst the highest levels were observed in subjects who were tall throughout their early life course. Adult height remained a significant predictor of IGF-I even after adjustment for earlier growth.

CONCLUSIONS

Our results indicate that IGF-I levels in early adulthood are associated with patterns of childhood growth as well as adult stature and adiposity. These associations suggest the IGFs may contribute to anthropometric associations with cancer risk.

Sexual dimorphism in the growth hormone and insulin-like growth factor axis at birth

In rodents and humans there is a sexually dimorphic pattern of GH secretion that influences the serum concentration of IGF-I. Pattern differences can be identified in children, but it is not known how early this difference is established. We studied the plasma concentrations of IGF-I, IGF-II, IGF-binding protein-3 (BP-3), and GH in cord blood taken from the offspring of 1650 singleton Caucasian pregnancies born at term and related these values to birth weight, length, and head circumference. Pregnancies complicated by preterm delivery, antepartum hemorrhage, pregnancy-induced hypertension, preeclampsia, or gestational diabetes and where cigarette smoking continued were excluded, resulting in a cohort of 987. Cord plasma concentrations of IGF-I, IGF-II, and IGFBP-3 were influenced by factors influencing birth size: gestational age at delivery, mode of delivery, maternal height, and parity of the mother. Plasma GH concentrations were inversely related to the plasma concentrations of IGF-I and IGFBP-3; 10.2% of the variability in cord plasma IGF-I concentration and 2.7% for IGFBP-3 was explained by sex of the offspring and parity. None of the factors, apart from maternal height, influenced cord serum IGF-II concentrations (adjusted r(2) = 1%). Sex of the baby, mode of delivery, and parity influenced cord serum GH concentrations (adjusted r(2) = 2.6%). Birth weight, length, and head circumference measurements were greater in males than females (P < 0.001). Mean cord plasma concentrations of IGF-I (males, 66.4 +/- 1.2 micro g/liter; females, 74.5 +/- 1.3 micro g/liter; P < 0.001) and IGFBP-3 (males, 910 +/- 13 micro g/liter; females 978 +/- 13 micro g/liter; P < 0.001) were significantly lower in males than females. Cord plasma GH concentrations were higher in males than females (males, 30.0 +/- 1.2 mU/liter; females, 26.9 +/- 1.1 mU/liter; P = 0.05), but no difference was noted between the sexes for IGF-II (males, 508 +/- 6 micro g/liter; females, 519 +/- 6 micro g/liter; P = NS). After adjustment for gestational age, parity, and maternal height, cord plasma concentrations of IGF-I and IGFBP-3 along with sex explained 38.0% of the variability in birth weight, 25.0% in birth length, and 22.7% in head circumference. These data demonstrate that in a group of singleton Caucasian babies born at term, cord plasma IGF-I, IGFBP-3, and GH concentrations relate to birth size, with evidence for sexual dimorphism in the GH-IGF axis.

Urinary insulin-like growth factor I in athletes, before and after physical exercise, and in sedentary subjects

BACKGROUND

Insulin-like growth factor I (IGF-I), like growth hormone (GH), is excreted in urine in a smaller fraction than the concentration found in blood. Exercising subjects undergo post-exercise proteinuria. The present work aims to propose a method for urinary IGF-I analysis (uIGF-I) by defining urinary concentration in sedentary individuals and athletes before and after strenuous exercise.

METHODS

Urine samples were collected from 30 sedentary healthy male individuals during the morning and from 30 well-trained cyclists, before and after a competition of about 3 h (150 km). uIGF-I was measured in undiluted acidified urine by radioimmunoassay (RIA) method using a purified polyclonal rabbit antibody, human 125I-IGF-I and a second anti-rabbit antiserum. The acidification of the urine samples and the excess of IGF-II addition in the incubation medium of the assay were used to dissociate the binding and to block the interference from IGF binding proteins (IGFBPs). Urinary growth hormone (uGH), total protein (utPr) and creatinine (ucr) concentrations were also measured by immunoradiometric assay (IRMA), colorimetric and capillary electrophoresis methods, respectively.

RESULTS

The analysis range was 0-2500 ng/l (0-327 pmol/l), the intra- and inter-assay coefficients of variations (CVs) ranged from 2.3% to 7.8%, respectively. The detection limit was 0.6 pg/tube. The uIGF-I/creatinine (cr) ratio in healthy subjects was 70 +/- 8 pg/mg cr. The uIGF-I/creatinine ratio (pg/mg cr) was different (p<0.001) in athletes before vs. after competition 93 +/- 27 vs. 136 +/- 13. Athletes' [uIGF-I/total proteins] ratio (ng/mg tPr) before and post-exercise was 2.3 +/- 0.5 and 2.5 +/- 0.3, respectively.

CONCLUSIONS

uIGF-I assay appears to be an effective way of monitoring IGF-I excretion. In the cyclists, in the pre-exercise state, uIGF-I was comparable with that measured in sedentary healthy individuals. In the cyclists, after strenuous exercise, the increased uIGF-I/cr and uGH/cr ratios suggested a relation with the post-exercise proteinuria. In conclusion, proteinuria physiologically obtained, such as post-exercise proteinuria, might be a new approach in IGF-I system investigation.