Effects of synthetic ovine corticotropin-releaseing factor (CRF) on plasma ACTH and cortisol in 31 normal human males.

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Abstract
Responses of plasma ACTH and cortisol to corticotropin-releasing factor (CRF) were evaluated in 31 normal human males. 1.0μg/kg of sterilized synthetic ovine CRF was administered to the subjects, aged 19 to 53 yr and weighing 50 to 78 kg, at between 9: 30 a.m. and 10: 30 a.m. as an intravenous bolus injection after an overnight fast. Blood specimens were drawn before and 15, 30, 60, 90 and 120 min after injection for later determination of plasma ACTH and cortisol concentrations by radioimmunoassays. Plasma ACTH and cortisol levels for all subjects rose significantly (p<0.001) from the basal level (mean±SEM, 26.8±4.5pg/ml and 12.6±0.9μ/dl) to peak levels (58.4±5.5pg/ml and 22.9± 1.0μg/dl) at 30 min and at 60 min, respectively. Although the plasma concentrations of ACTH and cortisol thereafter declined gradually, the levels at 120 min (43.4±5.2pg/ml and 18.9±0.9 μg/ml, respectively) were still significantly higher than the basal levels (p<0.001). Significant inverse correlations were observed between the basal levels of each hormone and the ratio of the peak level to the basal level (p<0.01), and the increases in plasma ACTH and cortisol concentrations were either not significant or much smaller for the individuals in whom the basal levels were higher than 65 pg/ml and 17.0μg/dl, respectively. No serious subjective symptom was observed during the experimental period in any of the subjects. These data indicate that intravenous injection of 1.0μg CRF significantly stimulates ACTH and cortisol secretion in normal subjects and thus appears to be useful in evaluating and investigating various disorders of the hypothalamic-pituitary-adrenal axis. However, the optimal dose and the most adequate time of administration of CRF for these purposes remain to be established.