*Produces high levels of serotonin and chromogranin-A in the blood.
** High levels of 5-HIAA (5-Hydroxy Indole Acetic Acid, a product of serotonin breakdown) in the urine. •
***Normal levels of serotonin and chromogranin-A in blood.
• Normal levels of 5-HIAA in their urine.
• High levels of urinary serotonin and the amino acid 5-hydroxytryptophan (5-HTP) because atypical lung carcinoid tumors can make 5-HTP.