Effects of RU 486 on energy expenditure and meal tolerance in normal men

To evaluate the possible actions of glucocorticoids on resting energy expenditure and the thermogenic response to food in man.

The morning after administration of RU 486 or placebo, resting metabolic rate (RMR) and the thermogenic response to food (TRF), were measured after the ingestion of a standardized meal in 12 healthy male volunteers. Plasma glucose (PG) and insulin (PI) concentrations were also measured at regular intervals.

1) After RU 486 administration, plasma cortisol was elevated throughout the test comparatively to placebo. 2) Fraction and concentration of free cortisol were also higher after RU 486 than after placebo. 3) Corticosteroid-binding-globulin (CBG) was similar in both experimentations. 4) RMR was not different after RU 486 (1656 +/- 144 kcal/day) or after placebo (1632 +/- 120 kcal/day). 5) TRF was not different after RU 486 or placebo (54 +/- 12 kcal vs 59 +/- 13 kcal over a 6 hour period for RU 486 and placebo, respectively). 6) Baseline glucose concentrations were similar at baseline but PG was higher 90 minutes postprandial with RU 486: 5.3 +/- 1.7 mmol/L vs 3.7 +/- 0.8 mmol/L for placebo. 7) Plasma insulin was similar at baseline but it was significantly higher at 90 minutes postprandial after RU 486 (347 +/- 143 vs 241 +/- 73 pmol/L for RU 486 and placebo, respectively).

This study shows that acute inhibition of glucocorticoid action does not alter RMR and TRF in healthy men and that a mild deterioration of glucose tolerance follows the ingestion of RU 486.