PMON257 Oral Ingestion of Macronutrients Selectively and Variably Decrease Circulating Testosterone Concentration in Healthy Men

Abstract We have previously reported acute suppression of testosterone in men after oral ingestion of dextrose. In the present study, we aimed to explore a potentially similar effect in response to other macronutrients. Eleven healthy men (age: 33-70 yrs, BMI 20.4-31.5 kg/m2) were studied in random order after an overnight fast on 4 separate days, involving oral ingestion of 300 ml of either water (control), dextrose, protein, or lipid solutions. Sessions were 6.5 h long, starting at 0800-0900 hrs. Test meals were isocaloric (400 kcal) and were ingested after the 4th blood draw (30 min point). Blood was collected at 10-min intervals for testosterone (ng/dL), and LH (IU/L) measurements. Means of the 1st 4 pre-intervention measures were used as the first value in all the time series. Mean delta-serum (macronutrients-water) testosterone and LH concentrations sampled at 10-minute intervals over 6 hour period were adjusted to the corresponding 1st value to correct for among the sessions inconsistent baseline testosterone and LH measures. Compared to the water day (control), mean (± SE) serum testosterone concentrations (ng/dL) in 11 subjects decreased from 415 ± 36 (control) to 370 ± 31 (dextrose: P=0.009), 340 ± 28 (protein: p=0.002), and 355 ± 30 (lipid: p=0.01). Corresponding LH (IU/L) values for dextrose (3.16 ± 0.29), protein (3.17 ± 0.39), and lipid (3.07 ± 0.29) were not significantly different from the control day (3.3 ± 0.29). Mean delta-testosterone time series revealed decreased testosterone of 63 ng/dL at 130 min after dextrose, 80 ng/dL at 200 min after protein, and 10 ng/dL at 70 min after lipid ingestion. Duration of suppression was variable among the 3 macronutrients, but most prolonged for protein lasting for 320 min. As oppose to testosterone, delta-LH concentrations were more positive rather than negative, suggestive of a potential testicular insult. In conclusion, oral ingestion of all macronutrients decrease circulating testosterone concentration, which appear to be independent of LH secretion. The effect is more intense and prolonged after protein intake, and minimal with lipid ingestion. Future studies are required to define the etiology, and the macronutrient effect on more prolonged basis. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.