Maturation of cortisol responses to adrenocorticotropic hormone in twin fetal sheep in vivo

Byline: William A. Block, Michael L. Draper, James C. Rose, Jeffrey Schwartz Keywords: Fetal development; adrenal gland; steroidogenesis; ovine Abstract: Objective: Adrenal steroidogenesis is important for maturation of fetal organ systems and plays a role in triggering parturition in ovine pregnancies. Studies have suggested a differential increase in baseline cortisol between twin gestations near term. Our aim was to further delineate the mechanisms responsible for the differences between the hypothalamic-pituitary-adrenal axes of twin fetuses in vivo. Study Design: Surgery was performed on pregnant ewes (n = 6) with twin gestations to implant fetal vascular catheters. After recovery but while the subjects were resting, plasma cortisol concentrations were similar in both fetuses. Fetuses received, intravenously, boluses of adrenocorticotropic hormone at 2 doses, and plasma samples were obtained for analysis of the cortisol response. This stimulation by adrenocorticotropic hormone was then repeated in the same fetuses approximately 4 days later, after the increase of resting daily cortisol values in one but not the other fetus. Results: Cortisol responses to adrenocorticotropic hormone before changes in daily resting cortisol concentrations were indistinguishable between twins. However, after separation of daily resting cortisol values, fetuses in group A (elevated resting cortisol concentration) demonstrated a significantly increased response to stimulation by adrenocorticotropic hormone. Conclusion: These results suggest a differential development in response to stimulation by adrenocorticotropic hormone between twin fetuses in vivo as the mechanism responsible for the asynchronous elevation of one twin's resting plasma cortisol concentration. (Am J Obstet Gynecol 1999;181:498-502.) Article History: Received 10 December 1998; Revised 24 February 1999; Accepted 31 March 1999 Article Note: (footnote) [star] From the Department of Obstetrics and Gynecology, the Department of Physiology and Pharmacology, and the Perinatal Research Laboratories, Wake Forest University School of Medicine., [star][star] Supported by National Institutes of Health grant HD11210-20., a Reprint requests: William A. Block, Jr, MD, Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, East Tennessee State University, Johnson City, TN 37614., aa 0002-9378/99 $8.00 + 0 6/1/98995