Daily cyclic changes in the urinary excretion of 5-hydroxyindoleacetic acid in patients with carcinoid tumors.

BACKGROUND

Vasoactive peptides produced by neuroendocrine tumors can induce characteristic symptoms of the carcinoid syndrome (flushing, diarrhea, and wheezing). To what extent external factors provoke these symptoms and how excretion of 5-hydroxyindoleacetic acid (5-HIAA), the degradation product of serotonin, varies throughout the day remain unknown. In this study, we investigated whether symptoms and daily activity are related to 5-HIAA excretion and whether 24-h urine collection is needed.

METHODS

In 26 patients with metastatic carcinoid (14 men and 12 women; median age, 60 years) urine was collected in portions of 4 or 8 h during 2 days. Patients were asked to keep a diary in which they noted symptoms of flushes, consistency of stools, activities, and food intake.

RESULTS

Excretion of 5-HIAA in 24-h urine was increased in 88% of the patients (median, 515 micromol/24 h). Overnight-collected urine appeared the most representative for 24-h collection concentrations (correlation coefficient = 0.81). We found no clear correlation between symptoms of the carcinoid syndrome and degree of activity. Watery diarrhea was reported only by patients with strong variations in 5-HIAA excretion. One-half of the patients (n = 16) exhibited a high variability in urinary 5-HIAA excretion throughout the day, with increased concentrations most prominent in morning collections (P = 0.0074) and lower concentrations in the evening (P = 0.0034). In the other patients these curves were flat.

CONCLUSIONS

Cyclic changes in patients relate to high variability in 5-HIAA excretion. Overnight-collected urine can replace the 24-h urine collection, and marked variations in 5-HIAA excretion seem to be associated with severity of diarrhea.