Vasopressin Test for Corticotrophin Release in Man

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Abstract
The vasoprssin test for corticotrophin (ACTH) release was studied in a group of volunteer subjects. The response of the plasma 17-OHCS [hydroxycorticosteroid] level to various dose levels and routes of administration of synthetic lysine vasopressin was compared. The effect on the clrcadlan rhythm and of pretreatment with dexamethasone or morphine was also studied. Intramuscular injection of physiologic saline did not cause any significant increase in the plasma 17-OHCS level. The mean maximal increment of the plasma 17-OHCS level was 3.4 /[mu]g/100 ml with 5 IU [international units], 14.0 [mu]g/100 ml with 10 IU and 17.4 [mu]g/100 ml with 20 IU. The corresponding value after intravenous injection of 10 IU was 14.2 [mu]g/100 ml, and after intravenous infusion of 200 mluAg body weight it was 22.2 [mu]g/100 ml. There was no significant circadian variation in the response to vasopressin injected intravenously or infused; the values at 9.00 and 17.00 hr. were 18.3 [mu]g/100 m1 to 21.0 [mu]g/100 ml and 14.2 [mu]g/100 ml to 22.2 [mu]g/100 ml, respectively. Two mg of dexamethasone 2 hr. before an intravenous injection of 10 IU of vasopressin did not inhibit the effect significantly, but 8 mg of dexamethasone in 2 days did. Morphine pretreatment had no significant effect on the vasopressin-induced increment of plasma 17-OHCS level. Cutaneous vasoconstriction and pallor appeared as side-effects in all the patients given vasopressin. There was also considerable gastrointestinal hypermotility, in some cases even defecation and vomiting. These symptoms displayed a definite correlation with the vasopressin dosage, however, less with infusion than with the other routes of administration. The results indicated that the vasopressin test is useful as a test of pituitary function of the release of ACTH to differentiate between pituitary and central nervous system disorders in cases with a limited capacity for ACTH secretion.