Responses to corticotropin-releasing hormone and its bound and free forms in pregnant and nonpregnant women

ABSTRACT Plasma CRH levels are considerably higher in women during the third trimester of pregnancy than in nonpregnant women. Most of plasma CRH in pregnant women is bound to CRH-binding protein (CRH-BP). To gain further insight into CRH physiology during pregnancy, we measured the responses of plasma ACTH and cortisol and the changes in bound and free forms of CRH in plasma after human CRH administration (2 μg/kg) in five pregnant (39–40 weeks of pregnancy) and five nonpregnant women. The mean basal plasma ACTH and cortisol levels in the pregnant women were higher than those in the nonpregnant women. However, the maximum increments in plasma ACTH and cortisol levels and the integrated ACTH and cortisol responses, after subtraction of the basal levels after CRH administration, were similar in the two groups. The plasma CRH half-time in the pregnant group was similar to that in the nonpregnant group. The mean basal plasma CRH level in the nonpregnant women was 1.5 ± 0.2 (±se) pmol/L, and that in the pregn...