Hypothalamus-pituitary-adrenal axis in central diabetes insipidus: ACTH and cortisol responsiveness to CRH administration

A strong relationship has been found between arginine-vasopressin (AVP) and hypothalamus-pituitary-adrenal axis in humans. The aim of the current study was to evaluate baseline and CRH-stimulated ACTH and F levels in patients with central diabetes insipidus (CDI), before and after replacement therapy with desamino-D-AVP (DDAVP). Twenty-five patients with CDI, and 25 sex- and age- and BMI-matched healthy subjects entered the study. A standard CRH test (measurement of plasma ACTH and serum F before and every 15 min for 2 h after the administration of 100 microg of human CRH) was performed in all subjects. In patients with CDI, CRH test were repeated after 1 week of DDAVP at standard doses. At study entry, ACTH and F levels were significantly higher in patients with CDI than in controls either at baseline (ACTH: 45.5+/-4.8 vs 18.5+/-3.3 ng/l, p<0.05; F: 375.1+/-55.7 vs 146.6+/-19.4 microg/l, p<0.05) or after CRH test considered as a peak (ACTH: 90.8+/-14.4 vs 42.5+/-7.4 ng/l, p<0.05; F: 501.6+/-65.7 vs 226.3+/- 25.6 microg/l, p<0.05) and AUC (ACTH: 3997.0+/-571.7 vs 2136.0+/-365.8 ng/l/120 min, p<0.05; F: 31,489.0+/-4299.4 vs 14,854.5+/-1541.5 microg/l/120 min, p<0.05). In patients with CDI, 1 week of replacement with DDAVP brought down ACTH (peak: 56.9+/-9.3 ng/l; AUC: 2390.7+/-480.7 ng/l/120 min) and F (peak: 310.3+/-39.5 microg/l; AUC: 17,555.5+/-2008.7 microg/l/120 min) responses to CRH to normal but did not significantly modify baseline hormone levels (ACTH: 29.6+/-3.6 ng/l; F: 239.0+/-32.3 microg/l). In conclusion, CDI is associated to increased baseline ACTH and F levels and increased responsiveness of ACTH and F to CRH administration. In addition, replacement treatment with DDAVP normalized CRH-induced but not baseline ACTH and F secretion.