Insulin-like growth factor I, insulin-like growth factor binding proteins, and growth hormone binding protein in Spanish premature and full-term newborns

The polymorphism of the ovine insulin like growth factor-2 (IGF2) gene and their associations with growth related traits in Tibetan sheep

In the current study, the role of the ovine IGF2 as a potential candidate gene was investigated as though marker-assisted selection in Chinese Tibetan sheep. The Sanger DNA sequencing method explored five single nucleotide polymorphisms (SNPs) in 5'UTR of the ovine IGF2 gene (C15640T, G15801A, G15870A, C15982G and G15991A) in Chinese Tibetan sheep. The frequencies of four SNPs were within the Hardy-Weinberg Equilibrium (chi-square test) except C15982G. The statistical analysis indicated that the C15640T and G15801A were significantly associated with body height, body length, chest circumference, and body weight (P < 0.05 or P < 0.01). Furthermore, C15982G variant exhibited significant correlation with the body weight (P < 0.01). These findings suggests that the promoter variants of IGF2 gene could be used as a candidate gene through marker-assisted selection for the body weight and body measurement traits in Tibetan sheep breeding program.

Pappalysins and Stanniocalcins and Their Relationship With the Peripheral IGF Axis in Newborns and During Development

CONTEXT

Pappalysins (PAPP-A, PAPP-A2) modulate body growth by increasing insulin-like growth factor I (IGF-I) bioavailability through cleavage of insulin-like growth factor binding proteins (IGFBPs) and are inhibited by stanniocalcins (STC1, STC2). Normative data on these novel factors, as well as on free IGF-I and uncleaved fractions of IGFBPs, are not well established.

OBJECTIVE

This work aimed to determine serum concentrations of PAPP-A, PAPP-A2, STC1, and STC2 in relationship with other growth hormone (GH)-IGF axis parameters during development.

METHODS

Full-term newborns (150; gestational age: 39.30 ± 1.10 weeks), 40 preterm newborns (30.87 ± 3.35 weeks), and 1071 healthy individuals (aged 1-30 years) were included in the study and divided according to their Tanner stages (males and females): I:163 males, 154 females; II:100 males, 75 females; III:83 males, 96 females; IV: 77 males, 86 females; and V:109 males,128 females.

RESULTS

Serum concentrations of PAPP-A, PAPP-A2, STC1, STC2, IGFBP-2, total IGFBP-4, and total IGFBP-5 were elevated at birth and declined throughout childhood. In postnatal life, PAPP-A2 concentrations decreased progressively in concomitance with the free/total IGF-I ratio; however, stanniocalcin concentrations remained stable. PAPP-A2 concentrations positively correlated with the free/total IGF-I ratio (r = +0.28; P < .001) and negatively with the intact/total IGFBP-3 ratio (r = -0.23; P < .001). PAPP-A concentrations inversely correlated with intact/total IGFBP-4 ratio (r = -0.21; P < .001), with PAPP-A concentrations being lower in females at all ages. Association studies indicate the importance of stanniocalcins and pappalysins in the control of this axis in an age-specific manner.

CONCLUSION

This study provides reference values of pappalysins and stanniocalcins, which modulate IGF-I activity by changing the concentrations of cleaved and uncleaved IGFBPs.

Changes in Serum Insulin-Like Growth Factors, Not Leptin, Are Associated With Postnatal Weight Gain in Preterm Neonates

BACKGROUND

Serum concentrations of conventional nutrition-related proteins, such as albumin, prealbumin, transferrin, and retinol-binding protein, are usually inconsistent with changes in anthropometric measurements in the postnatal period. The aim of this study was to evaluate how reliable growth hormone (GH), insulin-like growth factors (IGFs), IGF-binding proteins (IGFBPs), and leptin, the proteins known to be involved in the regulation of growth, are in reflecting postnatal growth and nutritional status in preterm neonates.

METHODS

Blood samples and anthropometric measurements were collected from 55 preterm neonates (chronological age 30.4 +/- 2.8 weeks) for 4 continuous weeks (weeks 0 to 3).

RESULTS

After adjusting for chronological age, body weights and serum IGF-II concentrations were significantly greater and serum transferrin concentrations were significantly lower in weeks 2 and 3 than in week 0 (repeated-measures analysis of variance (ANOVA) and Bonferroni test, p < .05). Forward stepwise multivariate regression analysis showed that change in total IGF-I (week 0 to week 3) was a positive predictor, and changes in insulin and prealbumin were negative predictors of postnatal weight gain. In addition, daily fat intake was a positive predictor of postnatal length increases, and changes in prealbumin, insulin, and GH were negative predictors of postnatal changes in the ponderal index (weight x length(-3)). Changes in GH and IGFBP-2 were negative predictors of changes in head circumference and triceps skinfold thickness, respectively.

CONCLUSIONS

Serial measurements of serum IGF-I and IGF-II may be useful adjuncts to anthropometric measurements for monitoring postnatal growth and nutritional status in preterm neonates.

Racial variation in umbilical cord blood sex steroid hormones and the insulin-like growth factor axis in African-American and white female neonates

PURPOSE

To evaluate whether there is racial variation in venous umbilical cord blood concentrations of sex steroid hormones and the insulin-like growth factor (IGF) axis between female African-American and white neonates.

METHODS

Maternal and birth characteristics and venous umbilical cord blood samples were collected from 77 African-American and 41 white full-term uncomplicated births at two urban hospitals in 2004 and 2005. Cord blood was measured for testosterone, dehydroespiandrosterone-sulfate, estradiol, and sex steroid hormone-binding globulin (SHBG) by immunoassay. IGF-1, IGF-2, and IGF-binding protein-3 (IGFBP-3) were measured by ELISA. Crude and multivariable-adjusted geometric mean concentrations were computed for the hormones.

RESULTS

African-American neonates weighed less at birth (3,228 g vs. 3,424 g, p < 0.004) than whites. Birth weight was positively correlated with IGF-1, IGFBP-3, and the molar ratio of IGF-1 to IGFBP-3, but inversely correlated with the molar ratio of IGF-2 to IGFBP-3. Adjusted models showed higher testosterone (1.82 ng/ml vs. 1.47 ng/ml, p = 0.006) and the molar ratio of testosterone to SHBG (0.42 vs. 0.30, p = 0.03) in African-American compared to white female neonates. IGF-1, IGF-2, and IGFBP-3 were lower in African-American compared to white female neonates, but only the difference for IGF-2 remained significant (496.5 ng/ml vs. 539.2 ng/ml, p = 0.04).

CONCLUSION

We provide evidence of racial variation in cord blood testosterone and testosterone to SHBG in African-American compared to white female neonates, and higher IGF-2 in white compared to African-American female neonates. Findings suggest plausible explanations for a prenatal influence on subsequent breast cancer risk and mortality. Further work is needed to confirm these observations.

Growth hormone, insulin like growth factor-1, and insulin-like growth factor-binding protein-3 levels in the neonatal period: a preliminary study

BACKGROUND

Growth hormone (GH), insulinlike growth factor-1 (IGF-1), and IGF-binding protein-3 (IGFBP-3) are used in the neonatal period for evaluation of diseases such as GH deficiency, intrauterine growth restriction, and hypoglycemia. However, GH level has been reported as a single value during the neonatal period. In this study, we attempted to determine the changes of GH, IGF-1, and IGFBP-3 in the neonatal period for each week.

METHODS

One hundred and two appropriate-for-gestational age (AGA) term neonates who did not have any diseases that would interfere with GH-IGF axis were included in this cross-sectional study. Blood samples were collected and serum GH, IGF-1 and IGFBP-3 levels were measured by immunoradiometric analysis (IRMA) and weekly values were obtained for the first postnatal four weeks.

RESULTS

We showed that GH level [median (1st-3rd quartile)] decreases from the first to the fourth postnatal week [25.1 (18.5-37.4); 17.2 (13.2-22.8); 17.6 (12.2-20.2); 14.4 (6.60-19.8) ng/mL, respectively)], IGF-1 and IGFBP-3 levels [median (lst-3rd quartile)] increase [41.7 (18.0-70.0); 55.9 (39.0-103); 53.0 (40.0-97.7); 71.7 (44.3-137) and 1852 (1597-2451); 2430 (1645-2838); 2841 (2280-3675); 3018 (2151-4189) ng/mL, respectively)].

CONCLUSIONS

GH, IGF-1 and IGFBP-3 values can be evaluated for each week separately instead of for the entire neonatal period.

Reduction of IGF-binding protein-3 as a potential marker of intra-uterine growth restriction

BACKGROUND

Growth factor-binding proteins influence the growth of infants starting in utero. Adaptation of the fetus to an adverse uterine environment is associated with changes in the growth hormone-growth factor-insulin axis.

AIMS

To evaluate serum levels of IGF-I and IGFBP-3 in small and appropriate for gestational age newborn infants.

METHODS

Fifty-four newborn infants, small (SGA, n=28) or appropriate (AGA, n=26) for gestational age were matched by gestational age and sex. Blood was collected on the first day of life, and anthropometric measurements were taken at birth. The serum levels of IGF-I and IGFBP-3 were compared, and correlated with the anthropometric measurements.

RESULTS

On the first day of life, mean serum IGFBP-3 levels were significantly lower in SGA babies and correlated with weight, length, head circumference, and ponderal index (weight/length 3) (P<0.0001). In contrast, no associations were found between IGF-I serum levels and these anthropometric measurements.

CONCLUSION

Our data show that SGA babies have significantly reduced IGFBP-3 concentrations at birth.

Influence of prematurity and growth restriction on the adipokine profile, IGF1, and ghrelin levels in cord blood: relationship with glucose metabolism

OBJECTIVE

To determine the influence of gestational age and fetal growth restriction on the cord blood adipokine profile, IGF1, and ghrelin levels, and their relationship with glucose metabolism.

STUDY DESIGN

One hundred and ninety newborns (99 preterm and 91 full term) were studied and, according to their anthropometry at birth, classified as small (SGA) or adequate for gestational age (AGA).

METHODS

Venous cord blood serum levels of IGF1, IGF binding protein 3 (IGFBP-3), adiponectin, resistin, leptin, soluble leptin receptor (sOB-R), tumoral necrosis factor-alpha, interleukin 6 (IL-6), total ghrelin, and acylated ghrelin were determined and compared between preterm and full-term, as well as between SGA and AGA, newborns. Correlations with newborn weight, gestational age, and homeostatic model assessment (HOMA) index, as an index of insulin resistance, were determined.

RESULTS

Preterm newborns had higher HOMA, sOB-R, resistin, and IL-6 and lower IGF1, IGFBP-3, leptin, and adiponectin levels than full-term newborns. SGA had lower IGF1, IGFBP-3, leptin, IL-6, and adiponectin and higher sOB-R and total ghrelin than AGA newborns. Adiponectin and HOMA showed independent positive and negative correlations with gestational age respectively, but not with neonatal weight. Birth weight was correlated positively with IGF1 and leptin levels and negatively with total ghrelin ones.

CONCLUSIONS

Our findings suggest that the lack of proper acquisition of adipose tissue by the fetus either due to prematurity or to fetal growth restriction is associated with changes in the cord blood adipokine profile that may contribute to the impairment of glucose metabolism.

Severe hypoinsulinaemic hypoglycaemia in a premature infant associated with poor weight gain and reduced adipose tissue

BACKGROUND

Hypoglycaemia is common in preterm and intrauterine growth retarded (IUGR) newborns. Although preterm and IUGR infants have limited adipose tissue stores, the role of adipose tissue and the associated adipocytokines in glucose physiology is not known.

AIM

We report the case of a premature intrauterine growth retarded infant who had poor weight gain for the first 6 weeks of life and then developed severe hypoinsulinaemic hypoketotic hypoglycaemia.

RESULTS

There was markedly reduced adiposity with low serum leptin and adiponectin levels. Total energy expenditure and body composition measurements showed that body fat as a percentage of weight averaged 7% at 20 weeks and 28% at 28 weeks. At 20 weeks of age, the patient was equivalent to a deficit of >2 SD scores of body fat, but average fatness by 28 weeks. The hypoglycaemia completely resolved when the patient started gaining weight with an increase in fat mass and a concomitant increase in serum leptin and adiponectin level.

CONCLUSIONS

Although the precise mechanism of this patient's severe hypoglycaemia is unclear, further studies are required to understand the role of adipose tissue and adipocytokines in glucose homeostasis in preterm and IUGR infants.

Insulin-like growth factor (IGF)-I and insulin in normal and growth-restricted mother/infant pairs

Insulin-like growth factor (IGF)-I and insulin are essential for fetal growth. We investigated perinatal changes of both factors in 40 mothers and their 20 appropriate-for-gestational-age (AGA) and 20 intrauterine-growth-restricted (IUGR) fetuses and neonates on day 1 (N1) and day 4 (N4) postpartum. Fetal and N1, but not N4, IGF-I levels were increased in AGA (P < .001 and P = .037, resp.). N1 insulin levels were lower in IUGR (P = .048). Maternal, fetal, and N1 IGF-I, and fetal insulin levels positively correlated with customized centiles (r = .374, P = .035, r = .608, P < .001, r = .485, P = .006, and r = .654, P = .021, resp.). Female infants presented elevated fetal and N4 IGF-I levels (P = .023 and P = .016, resp.). Positive correlations of maternal, fetal, and neonatal IGF-I levels, and fetal insulin levels with customized centiles underline implication of both hormones in fetal growth. IUGR infants present gradually increasing IGF-I levels. Higher IGF-I levels are documented in females.

Gap analysis of pediatric reference intervals related to thyroid hormones and the growth hormone–insulin growth factor axis

Efficacy of laboratory medicine in assisting attending physicians in their diagnostic and follow-up endeavors is intimately linked to an access to meaningful and reliable reference values. Pediatrics is particularly sensitive to this problem as the processes, associated with growth and development, are imposing rapid discontinuous changes on the physiology of the individuals. Some developmental stages are more critical than others. The neonatal and the pubertal periods, for which we lack reference ranges, are two such examples. Beyond biological considerations, we realize that, over the last 2 decades, technology has evolved, both at the analytical and reagent levels. This technological evolution inexorably leads to the need in redefining reference values. It is for this reason that a group of clinical and medical biochemists have joined their efforts in creating the Canadian Laboratory Initiative in Paediatric Reference (CALIPER) which objective is to define a pan-Canadian set of reference values from birth to late adolescence. To illustrate the need of such a venture, a brief gap analysis for biochemical variables related to the thyroid function, and the growth hormone-insulin-like growth factors axis follows.

The role of maternal factors, postnatal nutrition, weight gain, and gender in regulation of serum IGF-I among preterm infants

IGF-I is important for somatic growth and development of the human fetus and neonate. IGF-I also plays an important role in normal vascularization of human retina, as it has been suggested that insufficient IGF-I may be a factor in the development of retinopathy of prematurity. The principal regulator of the bioavailability of IGF-I in the circulation is IGF binding protein 3 (IGFBP-3). The aim of this study was to study factors associated with postnatal serum concentrations of IGF-I and of IGFBP-3 in preterm infants from birth to an age corresponding to 40 wk postmenstruation. We conducted a prospective, longitudinal study in which we measured serum IGF-I and IGFBP-3 concentrations in 76 preterm infants from birth (postmenstrual ages 23-32 wk) until discharge from hospital around 40 wk. Information regarding nutrition, weight gain, maternal factors, and treatment with corticosteroids were collected weekly. Variables found to be associated with postnatal change over time of serum IGF-I and IGFBP-3 were postmenstrual age (p<0.001), weight gain (standard deviation score) (p<0.001), and enteral intake of protein (p<0.001). Male gender was associated with lower IGF-I levels (p<0.001). The relationship between protein intake and IGF-I (and also between protein intake and IGFBP-3) was positive, as was the relationship between weight gain and IGF-I (and between weight gain and IGFBP-3). These results indicate that the degree of prematurity, low enteral protein intake, male gender, and slow weight gain are associated with a slower postnatal increase of IGF-I in preterm infants.

Relation of cord serum levels of growth hormone, insulin-like growth factors, insulin-like growth factor binding proteins, leptin, and interleukin-6 with birth weight, birth length, and head circumference in term and preterm neonates

OBJECTIVES

Fetal growth process is governed by multiple factors. We investigated the relation of insulin-like growth factors (IGFs), IGF binding proteins (IGFBPs), leptin, and interleukin-6 (IL-6) with intrauterine growth in preterm and term neonates.

METHODS

Thirty-eight preterm and 43 term neonates were recruited. Anthropometric measures were recorded and umbilical cord blood samples were collected at birth.

RESULTS

Birth weight (BW), birth length (BL), ponderal index, head circumference (HC), and cord serum levels of albumin, prealbumin, retinol-binding protein (RBP), total and free IGF-I, IGF-II, IGFBP-3, acid-labile subunit (ALS), and leptin were significantly lower, whereas levels of IGFBP-1, IGFBP-2, and IL-6 were significantly higher in preterm than in term neonates (P < 0.05). Total and free IGF-I, ALS, and leptin had significantly positive correlations, whereas IGFBP-2 had a significantly negative correlation, with BW and BL in preterm plus term neonates. Forward stepwise multivariate regression analysis showed that gestational age (GA), IGFBP-2, leptin, and free IGF-I are significant predictors of BW; GA, IGFBP-2, ALS, transferrin, and leptin are significant predictors of BL; and GA and free IGF-I are significant predictors of HC in preterm and term neonates.

CONCLUSIONS

Our results suggest that IGF-I, IGF-II, IGFBP-2, ALS, and leptin play important roles in intrauterine growth.

Onset of significant GH dependence of serum IGF-I and IGF-binding protein 3 concentrations in early life

Forty-eight normal full-term Chinese babies (25 boys and 23 girls) were followed up every 2 mo in the first year and every 3 mo during the second year of life for anthropometric measurements. Blood samples were taken at birth and at 6, 10, 12, and 18 mo after birth for serum GH-binding protein, IGF-I, and IGF-binding protein 3 analysis. Onset of the childhood phase of growth in the infants was determined from the growth data plotted on Infancy-Childhood-Puberty growth charts. The serum GH-binding protein concentrations were low in cord blood but rose significantly at 6 mo, with slower rises in late infancy and early childhood. However, a significant rise in serum IGF-I and IGF-binding protein 3 levels was only observed from 10 mo of life onward. The change in IGF-I between birth and 6 mo was significantly correlated with length gain (r(2) = 0.35, p < 0.05) and body mass index gain (r(2) = 0.41, p < 0.01) during the same period. The 34 infants with onset of childhood phase of growth between 6 and 10 mo had a higher mean serum IGF-I value at 10 mo (8.8 +/- 5.8 nM versus 4.9 +/- 3.1 nM; p < 0.05) and higher length velocity between 10 and 12 mo (16.3 +/- 4.7 cm/y versus 8.8 +/- 4.3 cm/y; p < 0.001) compared with the 14 infants with a later onset after 10 mo of age. A significant correlation between a change in serum IGF-I and IGF-binding protein 3 levels was observed during the three 6-mo periods between birth and 18 mo, but a significant correlation between a change in serum GH-binding protein and a change in serum IGF-I or IGF-binding protein 3 levels was only seen between 12 and 18 mo of age. The multiple regression analysis (r(2) = 0.43, p = 0.0002) revealed that the change in serum GH-binding protein and IGF-I concentrations between 6 and 12 mo of age and the age of onset of childhood phase of growth could explain 43% of the length gain between 6 and 12 mo of age in our babies. The results of our study support the hypothesis that the onset of the childhood phase of growth is associated with the onset of significant GH action on growth.

Growth restriction in dexamethasone-treated preterm infants may be mediated by reduced IGF-I and IGFBP-3 plasma concentrations

OBJECTIVE

Preterm infants receiving dexamethasone for respiratory morbidity frequently suffer restricted growth. The aim of this study was to investigate the interactions between dexamethasone treatment regimen and circulating IGFBP-3 and IGF-I levels, and the associations between these variables and linear growth rate in preterm babies receiving dexamethasone for chronic lung disease of prematurity.

DESIGN

A randomised, unblinded, clinical trial of two different courses of dexamethasone: a 42-day tapering course (the long course) and a repeatable 3 day pulse course.

PATIENTS

Forty preterm infants (19 in the pulse group, 21 in the long group) with a birthweight < or = 1250 g who were ventilated at 7 days of age.

MEASUREMENTS

Lower leg length was measured thrice weekly by knemometry, and IGFBP-3 and IGF-I levels were measured prior to commencing treatment, at 14 and 42 days of treatment and at 36 weeks postmenstrual age (PMA). Interactions between variables were analysed by stepwise regression analysis and analysis of covariance (ANCOVA). Associations between variables were assessed by correlation coefficients.

RESULTS

In an ANCOVA, mean daily dose of dexamethasone/kg (MDDD) and treatment group both significantly influenced IGFBP-3 levels (P = 0.0009 and P = 0.017, respectively), and tended to influence IGF-I levels similarly (P = 0.098 and P = 0.07). MDDD also significantly influenced mean daily increase in lower leg length (MDILL; P < 0.01). IGFBP-3 and IGF-I levels were significantly related to MDILL (ANCOVA: P < 0.01). The correlation coefficients for IGFBP-3 and IGF-I levels and MDILL were 0.2 and 0.3 (both P < 0.0001), respectively. IGFBP-3 and IGF-I levels were highly correlated (r(2) = 0.52, P < 0.0001) and both increased significantly with increasing PMA (P < 0.0001). IGF-I levels were higher in females (P = 0.036).

CONCLUSION

This study provides evidence that the growth-restricting effects of dexamethasone may be mediated, at least in part, via suppression of the IGF axis. Both dexamethasone dose and treatment regimen influence circulating IGF-I and IGFBP-3 levels, and both are important in inducing growth restriction.

Bone metabolism and circulating IGF-I and IGFBPs in dexamethasone-treated preterm infants

AIM

To characterize the ontogeny of circulating IGF-I, the IGF binding proteins (IGFBPs) and biochemical markers of bone turnover in dexamethasone (DEX)-treated preterm infants with chronic lung disease.

METHODS

Plasma and urine samples from 17 infants were obtained prior to DEX, after 9-12 days of DEX and 10 days after the completion of DEX to assess plasma IGF-I, IGFBPs, osteocalcin and urinary N-telopeptide. Nutrient intakes and growth were monitored from birth until term corrected age at which time body composition was evaluated by dual energy X-ray absorptiometry.

RESULTS

Although nutrient intakes did not differ during or after DEX, weight gain (115 vs. 174 g/week) and length gain (0.7 vs. 1.0 cm/week) were higher after DEX treatment. Plasma IGF-I, IGFBP-3 and osteocalcin increased over time. N-telopeptide was the only biochemical parameter which appeared to be suppressed during DEX (1342 nM bone collagen equivalents/mM creatinine vs. 2486 (pre-DEX) and 2292 (post-DEX)). At term corrected age, bone mineral content was lower in dexamethasone-treated infants compared to preterm and term reference infants.

CONCLUSION

Changes in circulating IGFBP-2 and IGFBP-3 paralleled the changes reported in non-steroid-treated infants; however, it remains uncertain whether the natural rise in IGF-I was suppressed by DEX treatment. Assessment of these circulating components provided limited insight into the mechanisms by which DEX alters growth and bone turnover.

Developmental pattern of fetal growth hormone, insulin-like growth factor I, growth hormone binding protein and insulin-like growth factor binding protein-3

AIMS

To evaluate the developmental pattern of fetal growth hormone (GH), insulin-like growth factor I (IGF-I), GH binding protein (GHBP) and IGF binding protein-3 (IGF-3); to determine the implications for fetal growth.

METHODS

Serum GH, IGF-I, GHBP and IGFBP-3 were measured in 53 fetuses, 41 aged 20-26 weeks (group A) and 12 aged 31-38 weeks (group B). Fetal blood samples were obtained by direct puncture of the umbilical vein in utero. Fetal blood samples were taken to rule out beta thalassaemia, chromosome alterations, mother to fetus transmissible infections, and for maternal rhesus factor. GHBP was determined by gel filtration chromatography of serum incubated overnight with 125I-GH. GH, IGF-I and IGFBP-3 were determined by radioimmunoassay.

RESULTS

Fetal serum GH concentrations in group A (median 29 micrograms/l, range 11-92) were significantly higher (P < 0.01) than those of group B (median 16.7 micrograms/l, range 4.5-29). IGF-I in group A (median 20 micrograms/l, range 4.1-53.3) was significantly lower (P < 0.01) than in group B (median 75.2 micrograms/l, range 27.8-122.3). Similarly, IGFBP-3 concentrations in group A (median 950 micrograms/l, range 580-1260) were significantly lower than those of group B (median 1920 micrograms/l, range 1070-1770). There was no significant difference between GHBP values in group A (median 8.6%, range 6.6-12.6) and group B (median 8.3%, range 6-14.3). Gestational age correlated positively with IGF-I concentrations (P < 0.0001) and IGFBP-3 (P < 0.0001) and negatively with GH (P < 0.0001). GHBP values did not correlate with gestational age. Multiple regression analysis showed a negative correlation between GH:IGF-I ratio and fetal growth indices

CONCLUSIONS

The simultaneous evaluation of fetal GH, IGF-I, IGFBP-3 and GHBP suggests that the GH-IGF-I axis might already be functional in utero. The progressive improvement in the efficiency of this axis in the last part of gestation does not seem to be due to an increase in GH receptors.