Enhanced adrenocorticotrophic hormone and cortisol responses to corticotrophin-releasing hormone in central idiopathic diabetes insipidus

Mazza E, Goffi S, Barchi P, Arvat E, Bellone J, Limone P, Ghigo E, Camanni F. Enhanced adrenocorticotrophic hormone and cortisol responses to corticotrophin-releasing hormone in central idiopathic diabetes insipidus. Eur J Endocrinol 1994;130:121–4. ISSN 0804–4643 It is well known that arginine vasopressin (AVP) exerts a stimulatory effect on adrenocorticotrophic hormone (ACTH) secretion. Moreover, there is consistent evidence that the hypothalamic AVP-secreting neurons are involved in the neuroregulation of ACTH secretion. With the aim to throw further light on the interaction between AVP and corticotrophin-releasing hormone (CRH) in the neuroregulation of ACTH secretion, in this study we compared the ACTH and cortisol responses to human CRH (100 μg iv as a bolus) in 18 normal subjects (15 females and three males, age 22–35 years) and seven patients with central isolated diabetes insipidus (six females and one male, age 16–40 years). Two patients were newly diagnosed and five had discontinued substitution therapy with desamino-D-AVP 24 h before testing. All had free access to water before and during the test period. The ACTH and cortisol responses to CRH were higher in subjects with diabetes insipidus than in controls, either when evaluated as peak values (ACTH, mean±sem: 17.0±1.2 vs 7.7±0.7 pmol/l, p=0.0003; cortisol: 611.3±59.4 vs 450.7±21.2 nmol/l, p=0.01) or area under curve values (ACTH: 672.5±75.7 vs 364.0±33.6 pmol·1−1·h−1. p=0.002; cortisol: 29158.0±2937.0 vs 23236.7±1052.1 nmol·l−1 · h−1, p=0.03). These results show that patients with diabetes insipidus have an exaggerated pituitary-adrenal response to CRH. This may be due to the fact that in diabetes insipidus AVP secretion from parvocellular neurons of the paraventricular nucleus in the hypophysial portal system is not impaired. Alternatively, AVP secretion may be defective in both magnocellular and parvocellular hypothalamic AVP-secreting neurons. In this case, it could be hypothesized that adjustment is made to the feedback regulatory mechanisms of the hypothalamic–pituitary–adrenal axis, so that the CRH–ACTH axis assumes a main role with respect to the AVP–ACTH axis. Franco Camanni, Divisione di Endocrinologia, Ospedale Molinette, corso Dogliotti 14, 10126 Torino. Italy