Adrenocorticotropic Hormone (ACTH) Stimulation and G Protein

Study Summary

Males and females may exhibit different responses to testing of adrenal function. The hormones responsible for controlling adrenal function are ACTH (adrenocorticotropic hormone or corticotropin) and CRH (corticotropin-releasing hormone). Adrenal function is tested with an ACTH stimulation test. ACTH stimulates the adrenal glands to produce cortisol. Cortisol levels are measured, and a certain peak level indicates normal adrenal gland function. Females may produce more cortisol in response to ACTH testing than males. This difference may be due to certain proteins, called G proteins. The hormones controlling adrenal function, ACTH and CRH, work through G proteins. Females may have more G proteins than males allowing for the increased cortisol response to ACTH stimulation. The investigators speculate that: 1. There may be differences in adrenal responsiveness to ACTH stimulation testing between healthy males and females. 2. ACTH and CRH induce their own function. 3. Sex differences in adrenal responsiveness to ACTH stimulation testing may be related to sex differences in G protein expression. In this study, cortisol, a hormone produced by the adrenal glands, will be measured before and after the administration of ACTH. This study will also measure G proteins. G proteins are found in the white blood cells. White blood cells from females may have more active G proteins than white blood cells from males. Sex differences may be augmented after exposure to ACTH.