Combined use of vasopressin and synthetic hypothalamic releasing factors as a new test of anterior pituitary function.

Nine normal volunteers and 15 patients with pituitary disorders were given a combined test of anterior pituitary function using four hypothalamic releasing factors and arginine vasopressin. Rapid sequential intravenous infusions of human corticotrophin releasing factor 100 micrograms, growth hormone releasing factor 100 micrograms, luteinising hormone releasing hormone 100 micrograms, and thyrotrophin releasing hormone 200 micrograms were administered. Arginine vasopressin (10 pressor units) was given intramuscularly at the same time. Plasma or serum samples were assayed for concentrations of cortisol, growth hormone, luteinising hormone, follicle stimulating hormone, prolactin, and thyroid stimulating hormone at multiple times for 120 minutes. No troublesome side effects occurred. The results of the releasing factor combined test with arginine vasopressin were compared in the same subjects with a conventional combined test using insulin together with thyrotrophin releasing hormone and luteinising hormone releasing hormone. No difference was observed in the basal and peak concentrations of luteinising hormone, follicle stimulating hormone, thyroid stimulating hormone, and prolactin. Both cortisol and growth hormone responses to the releasing factors with arginine vasopressin were much greater than those seen with insulin induced hypoglycaemia or the combined releasing factors without arginine vasopressin. Patients with pituitary hypo-function were similarly recognised in both studies. There was a rapid increase in all hormone values with a peak usually by 60 minutes. In most people adequate assessment of individual hormone reserves may be achieved using basal, 30 minute, and 60 minute samples. This new combined releasing factor test appears to be a safe, rapid, and useful test of anterior pituitary function.