title: Caloric restriction increases serum testosterone concentrations in obese male subjects by two distinct mechanisms.
abstract: The concentration of serum testosterone is mainly regulated by the testicular function, which is under control of the central hypothalamic-pituitary-gonadal axis. A certain amount of testosterone is converted into β-estradiol by adipose tissue. Obesity in men is often associated with decreased androgen levels. The aim of the present study was to examine the effect of caloric restriction on serum testosterone levels in obese men. Dietary intervention study was performed with a very low calorie diet (800 kcal/d) for 12 weeks. Thirteen obese human male subjects (median body mass index: 42.7 kg/m2) were included. Body composition was assessed by impedance analysis. Insulin sensitivity was estimated by leptin-to-adiponectin ratio (LAR). Testosterone (T), β-estradiol, albumin, sex hormone-binding globulin (SHBG), LH, and FSH serum concentrations were measured by enzyme immunoassays. Statistical analysis was performed on baseline and values after 3 months. Caloric restriction significantly increased total testosterone (6.97 nmol/l to 13.21 nmol/l; p=0.001) and SHBG (22.11 nmol/l to 42.12 nmol/l; p=0.001) concentrations in serum. This is caused by a significant improvement of the testicular function (LH/T: 0.36-0.20; p=0.005) and a significant reduction of the T/β-estradiol conversion rate (73.59-104.29; p=0.003). There was a significant negative correlation of improvement of testicular function and LAR (rs=-0.683 (p=0.042)). In obese men caloric restriction significantly increases the serum testosterone concentration. This is achieved by 2 distinct mechanisms, that is, improvement of testicular function and reduced conversion of testosterone to β-estradiol by aromatase activity of the adipose tissue.
authors.affiliation: Department of Internal Medicine I, University of Kiel, Kiel, Germany.
authors.forename: D M
authors.initials: DM
authors.lastname: Schulte
authors.affiliation: Institute of Medical Statistics, Informatics and Epidemiology, University of Cologne, Cologne, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Hahn
authors.affiliation: Center for Endocrinology, Diabetes and Preventive Medicine, University of Cologne, Cologne, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Oberhäuser
authors.affiliation: Department of Clinical Chemistry, University of Cologne, Cologne, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Malchau
authors.affiliation: Department of Internal Medicine, SCIVIAS Hospital St. Josef, Rüdesheim am Rhein, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Schubert
authors.affiliation: Endokrinologikum Göttingen, Göttingen, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Heppner
authors.affiliation: Department of Internal Medicine I, University of Kiel, Kiel, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Müller
authors.affiliation: Center for Endocrinology, Diabetes and Preventive Medicine, University of Cologne, Cologne, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Güdelhöfer
authors.affiliation: Center for Endocrinology, Diabetes and Preventive Medicine, University of Cologne, Cologne, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Faust
authors.affiliation: Center for Endocrinology, Diabetes and Preventive Medicine, University of Cologne, Cologne, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Krone
authors.affiliation: Department of Internal Medicine I, University of Kiel, Kiel, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Laudes
mesh_terms: D052242:Adiponectin / Q000097:blood; D000328:Adult; D031204:Caloric Restriction; D004958:Estradiol / Q000097:blood; D006801:Humans; D007333:Insulin Resistance; D020738:Leptin / Q000097:blood; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood*; D013737:Testis / Q000503:physiopathology; D013739:Testosterone / Q000097:blood*
chemical_list: D052242:Adiponectin; D020738:Leptin; D013739:Testosterone; D004958:Estradiol; D007986:Luteinizing Hormone