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J. G. Lewis, R. Ghanadian, and G. D. Chisholm

ABSTRACT

Serum 5α-dihydrotestosterone (DHT) and testosterone (T) were measured in 98 normal adult men aged between 20–80 years, separating T and DHT by thin layer chromatography and using a sensitive and reliable radioimmunoassay. In three age groups between 20–40, 40–60 and 60–80, the means ± sem for serum DHT were 84 ± 4, 79 ± 3 and 67 ± 3 (ng/100 ml) respectively. The corresponding values for testosterone were 559 ± 25, 491 ± 25 and 475 ± 28 (ng/100 ml). A significant decrease was observed in the DHT level of the 60–80 years age group compared to either the 20–40 (P < 0.01) or the 40–60 (P < 0.02) age groups. There was a moderate decline in the testosterone level of the 60–80 years age group compared to 20–40 years (P < 0.05) but there were no significant changes in the testosterone levels between other groups.

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G. Norstedt, B. Husman, A. Mode, P. Eneroth, U.J. Lewis, and J.-Å. Gustafsson

Abstract. The sex differentiated binding 125I-human prolactin (PRL) to rat liver membranes was studied and the present results extend our previous studies on induction of hepatic PRL receptors by growth hormone (GH). In prepubertal female rats, PRL receptor levels are low compared with those in mature female rat livers. Infusion of hGH during one week to 17-day-old female rats resulted in a receptor level typical of adult female rats. The time course of receptor disappearance in male rats treated with hGH was also studied. When the receptor-inducing hormone was removed, receptor levels in hGH-treated male rats returned to the normal level characteristic of male rats after approximately 96 h.

The specificity of various GH-like and PRL-like hormones in PRL receptor induction was studied in hypophysectomized rats. The PRL-like hormones were identified by measuring their potency to displace 125I-hPRL from a receptor preparation obtained from female rat livers, and the GH-like hormones were identified by their potency to increase body weight in hypophysectomized rats. Using similar doses of hormones it was found that in vivo administration of growth-promoting peptides (rGH, hGH, bGH) induced PRL receptors, whereas lactogenic hormones (rPRL, hPL) had a very small or no effect on PRL receptor induction. This suggests that binding to a type of GH receptor is the first step in PRL receptor induction.

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Sarah J Lewis, Debbie A Lawlor, Børge G Nordestgaard, Anne Tybjærg-Hansen, Shah Ebrahim, Jeppe Zacho, Andy Ness, Sam Leary, and George Davey Smith

Objective

Epidemiological studies have shown that low folate levels are associated with a high body mass index (BMI). These findings have potentially important health implications and warrant further investigation to determine whether a causal relationship exists and the direction of this relationship. The methylenetetrahydrofolate reductase (MTHFR) C677T TT genotype is associated with reduced folate availability and may be a surrogate for measuring folate levels. We sought to determine whether MTHFR C677T genotype was associated with obesity.

Design

We carried out our study on four populations from three longitudinal studies based in the UK and Denmark in which DNA for genotyping was obtained along with measures of obesity.

Methods

Our subjects were taken from the British Women's Heart and Health Study (BWHHS), the Avon Longitudinal Study of Parents and Children (two populations: mothers and children) and the Copenhagen City Heart Study. We performed analyses separately by population, and then carried out a meta-analysis, combining similar populations.

Results

Initial findings in the BWHHS suggested that the TT genotype may be associated with an increased risk of obesity BMI≥30, however, no association was found with BMI or central adiposity in this cohort. This genotype was not associated with obesity in our other cohorts.

Conclusions

Our results suggest that the initial positive finding with obesity in the BWHHS was a chance finding. Our findings do not support a causal effect of low folate on obesity.