The Effects of Age and Obesity on Postprandial Dynamics of Serum Testosterone Levels in Men

Frederique Van de Velde; Tim Reyns; Kaatje Toye; Tom Fiers; Jean-Marc Kaufman; Guy T'Sjoen; Bruno Lapauw


Clin Endocrinol. 2020;92(3):214-221. 

In This Article

Abstract and Introduction


Objective: Guidelines recommend using fasting samples to evaluate testosterone (T) levels in men, as free and total T levels decrease postprandially. However, it is not clear whether these dynamics are affected by age or obesity. This could be relevant given the obesity epidemic, ageing population and the barrier for screening which fasting could impose.

Design/Participants: A total of 43 men underwent a solid mixed meal tolerance test. Serum samples were taken fasting, and at 30, 60 and 120 minutes postprandially. A commercial immunoassay was used to determine sex hormone-binding globulin (SHBG) levels, liquid chromatography coupled to tandem mass spectroscopy for total T concentrations and free T levels were calculated.

Results: Postprandially, both total and free T were lower at all-time points compared with fasting (all, P < .005). At 60 minutes, maximum mean decreases of 15 ± 15% and 17 ± 16% were seen for total and free T levels, respectively. Younger men had greater decreases in both total and free T levels compared with men older than 40 years (all, P < .05). A greater decrease at 30 and 60 minutes postprandially was observed for both total and free T levels in nonobese vs obese men (all, P < .05).

Conclusions: After a mixed meal, total and free T serum levels decreased whereas SHBG levels did not change. Interestingly, postprandial decreases were less pronounced in men older than 40 years and/or with obesity. Although this study indicates less pronounced decreases in certain men, fasting samples remain a prerequisite for establishing correct diagnosis of male hypogonadism.


Most,[1,2] but not all,[3,4] clinical guidelines on diagnosis of hypogonadism in men recommend measuring fasting morning total testosterone (T) concentration, with confirmation of low T levels on a separate measurement before making a diagnosis of hypogonadism. Moreover, the analysis of T should be performed using an accurate and reliable assay.[1] As these preanalytical prerequisites might impose a barrier for screening, some studies investigated the importance of sampling in fasting condition. Indeed, most of these studies showed a decrease in total T levels after a glucose load[5–9] or fat-rich meal,[10–13] with some showing decreases in calculated free T levels while sex hormone-binding globulin (SHBG) levels remained unchanged[5,8,10,11,13] indicating postprandial changes in T production or clearance. However, until now, no study used liquid chromatography coupled with tandem mass spectroscopy (LC-MS/MS) to determine T levels and most studies used an oral glucose tolerance test (OGTT)[5–9] instead of a more physiologic standardized solid mixed meal[10,12,13] to address these postprandial changes. In addition, thus far it is not clear whether the decrease in T levels is similar in men with and without obesity or in younger vs older men. As older men and men with obesity have a disturbed functionality of the hypothalamic-pituitary-gonadal axis resulting in lower T levels,[14–17] it could be that in these populations postprandial dynamics of sex steroid levels are different than in a younger and/or leaner population. Moreover, the population continues ageing and the prevalence of obesity keeps rising. Therefore, this study aims at investigating the influence of age and obesity on postprandial changes of total T, free T and SHBG levels after a standardized mixed meal using LC-MS/MS and will evaluate whether this is of clinical relevance.