Neurohormonal responses to cholecystokinin tetrapeptide: a comparison of younger and older healthy subjects.

We recently found that, compared with younger healthy subjects, older healthy subjects had less symptomatic and cardiovascular response to the panicogenic agent cholecystokinin tetrapeptide (CCK-4). As an exploratory part of that study, we also evaluated the effect of aging on neurohormonal responses to CCK-4. These hormonal data are the focus of this article. Forty healthy volunteers aged 20-35 years and 40 healthy volunteers aged 65-81 years, divided equally between men and women, were compared on their hormonal responses (maximum change from baseline in growth hormone [GH], prolactin, adrenocorticotropic hormone [ACTH], and cortisol) to the intravenous administration of 50 microg of CCK-4 or placebo. Blood samples for serum hormone determination were collected at 2 minutes prior to the intravenous challenge (baseline) and at 2, 5, and 10 minutes after the challenge. In both age groups, maximum increase in prolactin, ACTH and cortisol was significantly greater with CCK-4 than with placebo. Following administration of CCK-4, younger and older groups did not significantly differ in maximum increase in prolactin, ACTH, or cortisol. Older subjects had a statistically significant smaller increase in GH compared with younger subjects but the magnitude of the difference was small and of doubtful clinical relevance. Older subjects who had a panic attack had significantly greater elevations of all hormones compared with those who did not panic and younger panickers had a significantly greater elevation of GH compared with young nonpanickers. For the most part, maximum changes in hormonal levels were not correlated with symptom severity, suggesting that other factors may have contributed to the differential effect of panic on the HPA axis.