Laboratory tests and measurements in children born small for gestational age (SGA)

Development of a bioassay system for human growth hormone determination with close correlation to immunoassay

Serum growth hormone (GH) level is measured largely through immunoassays in clinical practice. However, a few cases with bioinactive and immunoreactive GH have also been reported. We describe here a new bioassay system for GH determination using the BaF/GM cell line, which proliferates in a dose-dependent manner on hGH addition; cell proliferation was blocked by anti-hGH antibody. This bioassay had the lowest detection limit (∼0.02 ng/ml) reported thus far and the highest specificity for GH. The bioassay results were compared with those of an immunoradiometric assay across 163 patient samples in various endocrine states. A close correlation (the ratio of bioactivity/immunoreactivity was 1.04 ± 0.33, mean ± SD) was observed between bioactivity and immunoreactivity in these samples. The newly developed system is a specific, sensitive, easy, and fast bioassay system for GH determination; we consider it useful for evaluating GH bioactivity in various endocrine states.

Insulin-like growth factor-binding protein-1: serum levels, promoter polymorphism, and associations with components of the metabolic syndrome in short subjects born small for gestational age

CONTEXT

IGF binding protein (IGFBP)-1 is the only acute regulator of IGF-I bioavailability. Its production is suppressed by insulin, and low levels are associated with hyperinsulinemia and cardiovascular disease risk in adults. Data on IGFBP-1 levels in short, small for gestational age (SGA) subjects are scarce, and associations with IGFBP1 promoter single nucleotide polymorphisms have not been established.

OBJECTIVE

The aim of the study was to determine IGFBP-1 levels in short SGA subjects compared with those in controls, to assess genotype frequency of the -575 G/A single nucleotide polymorphism, and to determine its impact on IGFBP-1 levels.

SUBJECTS

A total of 272 short subjects born SGA and 330 subjects with normal stature (245 children, 85 young adults) participated in the study.

OUTCOME MEASURES

We measured fasting levels of IGFBP-1, IGF-I, insulin and lipid parameters, and body composition.

RESULTS

IGFBP-1 sd score (SDS) was comparable to controls in lean, short, SGA children but significantly lower in short SGA adults with normal fat mass (P < 0.001). IGFBP-1 SDS correlated significantly with insulin levels, systolic blood pressure SDS, and various lipid parameters. Baseline IGFBP-1 SDS was lowest in SGA children with -575 GG genotype and significantly higher in SGA children with one or two copies of the A allele. In response to a given insulin level, children with the AA genotype had a significantly higher IGFBP-1 SDS compared to children with the GG genotype.

CONCLUSION

Normal IGFBP-1 levels in lean, short, SGA children may reflect a normal metabolic state, despite reported hyperinsulinemia. IGFBP-1 is modulated by polymorphic variability and seems to be an additional player in the complex interaction between the IGF-IGFBP axis, glucose homeostasis, and lipid metabolism.

Serum adiponectin and leptin levels and insulin resistance in children born large for gestational age are affected by the degree of overweight

OBJECTIVE

Children born large for gestational age (LGA) are prone to develop insulin resistance later in life. One factor that affects insulin sensitivity is the hormone adiponectin. The aim of this study was to determine whether being LGA has an impact on serum adiponectin and leptin levels and insulin resistance parameters during childhood, taking into account the severity of overweight.

STUDY DESIGN

Serum levels of adiponectin, leptin, fasting glucose and insulin, homeostasis model assessment insulin resistance index (HOMA-IR), and anthropometric indices were evaluated in groups of non-obese children aged 6.5-8 years, born appropriate for gestational age (AGA, n = 40) or LGA (n = 41), matched for age, gender, height, weight and body mass index. The LGA group was divided in two subgroups according to the degree of overweight: (a) LGA with birthweight 90th-97th percentile (n = 25); and (b) LGA with birthweight > 97th percentile (n = 16).

RESULTS

LGA children had a higher mean serum adiponectin level than AGA children: 17.0 +/- 9 vs. 11.1 +/- 5 (microg/ml) (P < 0.01). LGA children had also higher insulin 6.2 +/- 2.8 vs. 4.8 +/- 2.4 (microU/ml) (P < 0.05) and HOMA-IR 1.32 +/- 0.66 vs. 1.02 +/- 0.55 (P < 0.01) than AGA children. Children born LGA > 97th percentile had a significantly higher mean serum leptin level than both AGA and LGA 90th-97th percentile children (17 +/- 13, 9.6 +/- 9.5, 7.8 +/- 7.9 ng/ml, respectively, P < 0.05), and more severely affected insulin resistance indices than LGA 90th-97th percentile children. In the regression analysis, birthweight was found to be an independent predictor of adiponectin serum levels.

CONCLUSION

Prepubertal LGA-born children had a higher mean serum adiponectin levels than matched AGA controls despite the fact that they were more insulin resistant. The degree of excess in utero weight gain appears to influence the metabolic profile in LGA-born prepubertal children. Further studies are needed to delineate the role of adiponectin in the risk of development of insulin resistance in children born LGA.

Management of the child born small for gestational age through to adulthood: a consensus statement of the International Societies of Pediatric Endocrinology and the Growth Hormone Research Society

OBJECTIVE

Low birth weight remains a major cause of morbidity and mortality in early infancy and childhood. It is associated with an increased risk of health problems later in life, particularly coronary heart disease and stroke. A meeting was convened to identify the key health issues facing a child born small for gestational age (SGA) and to propose management strategies.

PARTICIPANTS

There were 42 participants chosen for their expertise in obstetrics, peri- and neonatal medicine, pediatrics, pediatric and adult endocrinology, epidemiology, and pharmacology.

EVIDENCE

Written materials were exchanged, reviewed, revised, and then made available to all. This formed the basis for discussions at the meeting. Where published data were not available or adequate, discussion was based on expert clinical opinions.

CONSENSUS PROCESS

Each set of questions was considered by all and then discussed in plenary sessions with consensus and unresolved issues identified. The consensus statement was prepared in plenary sessions and then edited by the group chairs and shared with all participants.

CONCLUSIONS

The diagnosis of SGA should be based on accurate anthropometry at birth including weight, length, and head circumference. We recommend early surveillance in a growth clinic for those without catch-up. Early neurodevelopment evaluation and interventions are warranted in at-risk children. Endocrine and metabolic disturbances in the SGA child are recognized but infrequent. For the 10% who lack catch-up, GH treatment can increase linear growth. Early intervention with GH for those with severe growth retardation (height sd score, <-2.5; age, 2-4 yr) should be considered at a dose of 35-70 microg/kg x d. Long-term surveillance of treated patients is essential. The associations at a population level between low birth weight, including SGA, and coronary heart disease and stroke in later life are recognized, but there is inadequate evidence to recommend routine health surveillance of all adults born SGA outside of normal clinical practice.