Andrologia. 2012 Dec;44(6):405-10. doi: 10.1111/j.1439-0272.2012.01296.x. Epub 2012 Apr 23.
S-testosterone decrease after a mixed meal in healthy men independent of SHBG and gonadotrophin levels.
Lehtihet M, Arver S, Bartuseviciene I, Pousette A.
SourceKarolinska Institute, Centre for Andrology and Sexual Medicine, Karolinska University Hospital, Stockholm, Sweden.
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.