THE PENTAGASTRIN TEST IN THE DIAGNOSIS OF THE CARCINOID-SYNDROME - BLOCKADE OF GASTROINTESTINAL SYMPTOMS BY KETANSERIN

Google Scholar
  • 1 January 1985
    • journal article
    • research article
    • Vol. 201  (1) , 81-86
Abstract
The levels of 5-hydroxytryptamine (serotonin, 5-HT) and substance P (SP) were assayed (using high performance liquid chromatography-electron capture and radioimmunoassay methods) in the peripheral blood of 17 patients with known mid-gut carcinoids, 16 of whom had hepatic mestases. All patients had supranormal basal levels of 5-HT and SP. The clinical and hormonal changes induced by 2 provocation tests, i.v. pentagastrin (PG) and Ca infusion, were compared. Pentagastrin caused flushing in all the patients, induced gastrointestinal symptoms in all but 1 of the patients with hepatic involvement and universally elevated circulating 5-HT levels. Pretreatment with a 5-HT2-receptor blocking agent, ketanserin, abolished the gastrointestinal effects but had virtually no influence on either 5-HT levels or flushing induced by i.v. pentagastrin. In contrast, Ca infusion induced carcinoid symptoms in only 2 of 6 patients, and this was consistently associated with stimulation of circulating serotonin levels. 5-HT may be responsible for the gastrointestinal symptoms in carcinoid patients, but it does not seem to play any role in flushing; ketanserin may be a useful therapeutic agent in alleviating gastrointestinal symptoms in carcinoid patients; differential responses to PG suggests that SP is released from a site different from that of 5-HT; it is possible that SP may contribute to the mediation of flushing, but it cannot be the sole agent causing this symptom; and the pentagastrin test with measurements of 5-HT levels in peripheral blood seems to be superior to Ca infusion as a provocative test in documenting the diagnosis of carcinoid disease.