DIFFERENCES IN THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS OF BLACK-AND-WHITE MEN

We previously found that, following intravenous administration of ovin e corticotropin-releasing hormone (CRH), the plasma ACTH concentration s of Black women were approximately twice as high as those of White wo men; however, there were no corresponding differences in cortisol resp onse. To determine whether this difference in ACTH secretion is also p resent in men, we studied the hypothalamic-pituitary-adrenal axis of 1 0 Black and 10 White weight-, age-, and education-matched men. Waist-t o-hip ratio, 24-hour urine free cortisol excretion, and ACTH and corti sol responses to 1 mu g/kg ovine CRH were determined. There were no ra cial differences in waist-to-hip ratio, 24-hour urine free cortisol ex cretion, baseline free or total plasma cortisol and ACTH concentration s, or plasma cortisol response to CRH. However, CRH-stimulated plasma ACTH concentrations, measured in an extraction polyclonal radioimmunoa ssay, were significantly greater in Blacks than in Whites at all time points between 30 and 180 min after administration of CRH (area under curve (AUG) 1,796 +/- 245 pmol/l . min in Blacks vs. 1,278 +/- 121 pmo l/ l . min in Whites, p < 0.001). Neither cortisol nor ACTH AUCs were significantly correlated with Body Mass Index in Black or White men. W e conclude that there are differences in the HPA axis of Black and Whi te men similar to those found previously in women. The physiology unde rlying these differences remains to be understood.