Adrenocorticotropin Release by Tryptophan in Man*

Abstract

Previous work from this laboratory indicated significant elevations of cortisol after the administration of tryptophan. The current investigation was designed to confirm this observation and study the effect of this agent on ACTH. Cortisol rose 12.4 +/- 5.2 microgram/dl (mean +/- SD) in 10 of 12 tests (P less than 0.02). Responding patients had rises of ACTH averaging 101.8 +/- 45.8% (range, 40-159 pg/ml) above baseline. The time course of the ACTH change closely paralleled that of cortisol, and there were significant correlations between the rises of the two substances (r = 0.81; P less than 0.01). The current data strongly suggest that tryptophan administration stimulates ACTH release, possibly through activation of the central serotonergic nervous system. Review of the literature suggests the possibility that ACTH stimulation only occurs at high plasma tryptophan (and presumably brain serotonin) concentrations, with ACTH inhibition occuring at lower levels.

Pituitary Hormone Release in Response to Food Ingestion: Evidence for Neuroendocrine Signals from Gut to Brain*

“…There is evidence that brain concentrations of tyrosine and tryptophan increase after their oral ingestion and that the biosynthesis of catecholamine and serotonin is accelerated (23,25,26). Since the hypothalamic control of PRL and ACTH-cortisol secretion involves catecholamines and serotonin (16,(27)(28)(29)(30)(31), the ingested neurotransmitter substrate may serve as a neuroendocrine link between gut and brain.…”

Food‐induced Cortisol Secretion Is Mediated by Central Alpha‐1 Adrenoceptor Modulation of Pituitary Acth Secretion

“…Neither drug interfered with nutrient absorption; we chose tryptophan as an index of protein absorption as it is an amino acid that has been shown to stimulate cortisol secretion in man (Modlinger et al, 1980). The finding that ACTH and cortisol secretion is clearly reduced by thymoxamine confirms that postprandial ACTH secretion is mediated at least in part by alpha-l adrenoceptors.…”

Urinary free cortisol secretion in habitually violent offenders

“…Also in man, 5-HTP increases plasma ACTH (3) and cortisol (3,4). Increased cortisol and ACTH after oral L-tryptophan have also been reported (5,6). The antiserotonin agents, metergoline and cyproheptadine, inhibit metyrapone-induced ACTH secretion (7, 8) and insulin hypoglycemia-stimulated cortisol secretion (9).…”

“…Received October 6,1984; accepted for publication January 5, 1985 Various pharmacological studies have supported the postulated stimulatory role of brain serotonin neurons in the hypothalamic regulation of pituitary adrenocortical functions in laboratory animals. The hypothalamic corticotropin-releasing factor (CRF), which regulates ACTH secretion, is partly regulated by serotonin (1).…”