This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Diagnosis of carcinoid tumour is done Urinary estimation of: 
Select and explain. 
A. VMA, B. Metanephrines, C. Catecholamines, D. 5HIAA
D: 5HIAA
Answer: D: 5HIAA 
Explanation: Answer is D (5HIAA): Carcinoid Tumors Carcinoid tumors are associated with elevated levels of metabolites of Tryptophan/ serotonin which include 5HIAA, 5HT and5HTP. Pheochromocytomas Pheochromocytomas are associated with elevated levels of catecholamines and their metabolites which include Vanillylmandelic acid (VMA)and metanephrines The diagnosis of Typical carcinoid syndrome is suggested by elevated levels of 5HIAA The diagnosis of Atypical Carcinoid Syndrome is suggested by elevated levels of 5HTP. established by elevated levels of 5HIAA.