Serum leptin concentrations in a normal population and in GH deficiency: negative correlation with testosterone in men and effects of GH treatment.
OBJECTIVE
To study relationships between leptin and factors regulating body composition as well as metabolic risk factors. Furthermore, to study the effects of GH on leptin.


METHODS
Cross-sectional and population-based. Regarding the effects of GH, prospective and interventional.


METHODS
One hundred and eleven women and 107 men, 20-70 years old, randomly selected from the population registry in the community of Linköping, Sweden. Ten GH-deficient subjects were given GH until normalization of IGF-I levels.


METHODS
Venous blood was drawn in the fasting state. Serum leptin and hormones were analysed by immunoassay.


RESULTS
In the population sample the natural logarithm of leptin (in(leptin)) correlated with body mass index (BMI) (men, r = 0.67), P < 0.0001; women, r = 0.71, P < 0.0001). The median value of leptin was 4.6 micrograms/l in men and 12.3 micrograms/l in women (P < 0.0001). Levels of in(leptin) did not correlate with plasma neuropeptide Y (men, P = 0.13; women, P = 0.35). In men only there was an inverse relationship between in(leptin) and testosterone (r = -0.46, P < 0.0001, after correction for BMI standardized r = -0.26, P = 0.03) as well as IGF-I (r = -0.20, P = 0.048). Although BMI was similar, smoking men had higher leptin levels than non-smoking men (median, 6.6 and 4.2 micrograms/l, respectively; Mann-Whitney; P = 0.006). In the GH-deficient subjects leptin levels were elevated and, although GH treatment did not change BMI, leptin levels decreased (median before GH, 21 micrograms/l and after 15 micrograms/l, respectively; P = 0.017).


CONCLUSIONS
Serum leptin concentration is closely associated with BMI in the population with a gender difference in absolute levels and a strong negative correlation with testosterone in men. Serum leptin is elevated in GH deficiency and lowered by GH substitution.
Nyström
F
F
Department of Endocrinology and Metabolism, Faculty of Health Sciences, University Hospital, Linköping, Sweden. fredrick.nystroem@linkoping.mail.telia.com
Ekman
B
B
Osterlund
M
M
Lindström
T
T
Ohman
K P
KP
Arnqvist
H J
HJ
D000328:Adult; D015415:Biomarkers / Q000097:blood; D001823:Body Composition; D015992:Body Mass Index; D005260:Female; D013006:Growth Hormone / Q000097:blood / Q000172:deficiency* / Q000627:therapeutic use; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D020738:Leptin; D008297:Male; D008875:Middle Aged; D011506:Proteins / Q000032:analysis*; D012737:Sex Factors; D012907:Smoking; D018709:Statistics, Nonparametric; D013739:Testosterone / Q000097:blood*
D015415:Biomarkers; D020738:Leptin; D011506:Proteins; D013739:Testosterone; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone