Effect of dexamethasone on cortisol and prolactin responses to meals in bulimic and normal women.

In normal individuals, serum cortisol and prolactin concentrations have been shown to rise following a mid-day meal. To determine whether abnormalities of the hypothalamo-pituitary-adrenal axis in bulimics lead to a disrupted hormonal response to eating, cortisol and prolactin responses to meals (600 kcal, 30% protein, 30% fat, 40% carbohydrate) were studied on two consecutive days in six normal weight bulimics and six normal volunteers. Dexamethasone (1 mg orally) was administered at 2330 h after baseline sampling. During baseline sampling, cortisol concentrations were significantly higher in the bulimics (18.2 +/- 0.9 micrograms/dl, mean +/- SEM) than in the normals (12.1 +/- 0.4 micrograms/dl) (p less than 0.001). Post-dexamethasone cortisol concentrations also were higher in the bulimics (5.7 +/- 0.3 micrograms/dl) than in the normals (1.2 +/- 0.2 micrograms/dl) (p less than 0.001). The three bulimics with a major depressive disorder had higher peak post-dexamethasone cortisol concentrations than the nondepressed bulimics. Dexamethasone significantly enhanced the prolactin response to meals among both bulimics (at 90 min post onset of eating) and normals (at 60, 75 and 90 min post onset of eating). This enhancement of the prolactin response to meals by dexamethasone is opposite to the inhibitory effect of dexamethasone on stress-induced prolactin release and suggesting that stress-induced and meal-induced prolactin release involve different neuroendocrine mechanisms.