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Simon Kayemba-Kay's, Michael P P Geary, Jane Pringle, Charles H Rodeck, John C P Kingdom and Peter C Hindmarsh

Background

Low birth weight (BW), small head circumference, reduced length, increased preterm births and neuro-endocrine dysfunctions are among known consequences of smoking during pregnancy. Few studies have linked leptin to clinical features of growth restriction associated with maternal smoking and explored interaction with other determinants of size at birth, such as gender.

Methods

Cord serum leptin concentrations were measured in 1215 term infants born to Caucasian mothers at completion of uneventful pregnancy. Serum concentrations were related to BW, gestational length, gender and maternal smoking and interaction with other determinants of size at birth evaluated.

Results

Smoking was more frequent in younger (P<0.001) and shorter mothers (P=0.03) from lower socio-economic groups (SEGPs) (P<0.001). Infants born to smokers were lighter (190 g less), shorter and with smaller head circumference. Cord serum leptin concentrations were higher in girls (9.8 s.d. 7.6 ng/ml) than in boys (7.05 s.d. 5.8 ng/ml) (P<0.001). Boys were heavier (BW 3.52 s.d. 0.49 kg) than girls (3.39 s.d. 0.44 kg) (P<0.001), but girls had greater skinfold thickness measurements (sub-scapular and quadriceps skinfold thicknesses 5.5 s.d. 1.6 mm and 7.6 s.d. 1.9 mm respectively; boys 5.3 s.d. 1.6 vs 7.24±1.90 mm, P<0.001 respectively). Multivariate analyses showed gender (P<0.001), BW SDS (P<0.001), gestational length (P<0.001) and maternal smoking (P<0.042) as factors that influenced umbilical cord serum leptin concentrations in newborns.

Conclusion

Maternal smoking restrains foetal growth through placental vascular effects, and likely also via associated effects on leptin metabolism. More studies are needed to determine the influence that maternal smoking may have on placental syncytiotrophoblast and foetal adipose tissue.

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Mehul T Dattani, Andrew P Winrow, Anatoly Tuil'Pakov, P Jane Pringle, Peter C Hindmarsh, Charles GD Brook and Nicholas J Marshall

Dattani MT, Winrow AP, Tuil'Pakov A, Pringle PJ, Hindmarsh PC, Brook CGD, Marshall NJ. Evaluation of growth hormone (GH) responses to pulsed GH-releasing hormone administration using the MTT–ESTA bioassay. Eur J Endocrinol 1996;135:87–95. ISSN 0804–4643

We compared the immunoactivity of human growth hormone (hGH) with its bioactivity after stimulation of hGH release into the circulation by the administration of growth hormone-releasing hormone [GHRH(1–29)-NH2] according to a pre-determined protocol to four normal adult volunteers. We used the Hybritech immunoradiometric assay to measure the immunoactive GH concentrations. Bioactive GH concentrations were measured using the highly quantitative and precise eluted stain bioassay system (ESTA). The high sample capacity of the ESTA bioassay permitted us to monitor the bioactivities in closely timed sequential samples, and in far greater detail than has previously been possible. Two pulses of GHRH(1–29)-NH2 were administered intravenously to the four adult male volunteers (aged 24–37 years) on a weekly basis over a 4-week period. Two different doses of GHRH(1–29)-NH2 (0.1 and 1.0 μg/kg) were tested. These were separated by specified time intervals (60 or 120 min). Responses in the four individuals were variable. However, although the immunoand bioactivities generally agreed well, there was a systematic and progressive increase in the bioactivity/immunoactivity (B/I) ratios as half of the response peaks were approached. After these peak concentrations, the B/I ratios subsequently returned to values that were close to unity. The enhanced bioactivity of the peak samples from the two volunteers in whom the largest magnitudes of response were observed was found to be labile after long-term storage at −20°C. We suggest that the preferential rise in GH bioactivity, as opposed to immunoactivity, in response to GHRH(1–29)-NH2 was due to progressive changes in the concentrations of isoforms of GH that are not detectable in the Hybritech immunoassay.

NJ Marshall, Division of Molecular Pathology, University College London, The Windeyer Building, 46 Cleveland Street, London W1P 6DB, UK