title: S-testosterone decrease after a mixed meal in healthy men independent of SHBG and gonadotrophin levels.
abstract: Reproducible and accurate assessment of serum testosterone (S-T), S-LH and S-SHBG is of crucial importance for assessment of testicular endocrine function and diagnosis of hypogonadism and investigating male health in a broader sense. Testosterone secretion has a circadian rhythm with the highest component in the morning and is influenced by a series of factors including physical activity, mental stress and nutrition. For diagnostic purposes, analysis of morning samples is recommended and reference values are generally based on samples drawn between 7 and 10 am. In the literature, there are also indications that food intake can influence serum levels but fasting has not been a standard procedure. To carefully address the influence of food intake, we analysed S-testosterone, S-LH and S-SHBG after an overnight fasting compared to samples taken after a standard meal of 550 kcal. We found no change in S-LH or S-SHBG but a decline of S-T of 30% from 60 to 120 min after food intake compared to samples taken in the fasting state. This decline may give false low S-T values and overestimate the number of men with suspected hypogonadism. Until the mechanism behind this effect has been explored, we suggest that assessment of S-T for diagnostic purposes should be collected in the morning after an overnight fasting.
authors.affiliation: Karolinska Institute, Centre for Andrology and Sexual Medicine, Karolinska University Hospital, Stockholm, Sweden. mikael.lehtihet@ki.se
authors.forename: M
authors.initials: M
authors.lastname: Lehtihet
authors.forename: S
authors.initials: S
authors.lastname: Arver
authors.forename: I
authors.initials: I
authors.lastname: Bartuseviciene
authors.forename: A
authors.initials: A
authors.lastname: Pousette
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D002940:Circadian Rhythm / Q000502:physiology; D004435:Eating / Q000502:physiology*; D005058:Eunuchism / Q000097:blood / Q000175:diagnosis; D005189:False Positive Reactions; D005215:Fasting / Q000097:blood; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D008875:Middle Aged; D019518:Postprandial Period / Q000502:physiology; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism*; D013739:Testosterone / Q000097:blood*
chemical_list: D001786:Blood Glucose; D012738:Sex Hormone-Binding Globulin; D013739:Testosterone; D007986:Luteinizing Hormone