Biochemical assessment of niacin deficiency among carcinoid cancer patients.
OBJECTIVE
Carcinoid cancer patients often have elevated levels of serotonin or its precursor 5-hydroxytryptophan. Normally, serotonin synthesis accounts for a small fraction of tryptophan catabolism, which should be directed along a pathway that allows partial conversion to niacin; hence, increased diversion of tryptophan toward serotonin could cause variable degrees of niacin deficiency in carcinoid patients. Therefore, the prevalence of niacin deficiency among carcinoid patients was investigated by clinical assessment of pellagra and biochemical assessment of whole blood niacin number, a ratio derived from two biologically active forms of niacin (NAD/NADP x 100).


METHODS
Clinical and biochemical niacin status were assessed in a cohort of newly diagnosed carcinoid patients with carcinoid syndrome (CCS, n = 36), carcinoid patients without carcinoid syndrome (CWCS, n = 32) and noncarcinoid controls (n = 24) recruited at two primary care clinics. Other aspects of serotonin metabolism were measured by analyses of plasma serotonin and tryptophan and urinary excretion of 5-hydroxyindoleacetic acid.


RESULTS
Biochemical niacin deficiency (niacin number < 130) was significantly more common in CCS patients (10 out of 36) compared to controls (p < 0.05, Fisher's exact test), while CWCS patients displayed an incidence that was not significantly elevated (4 out of 32). Only one CCS patient, who was also identified biochemically as niacin deficient, was clinically diagnosed with pellagra.


CONCLUSIONS
Biochemical niacin deficiency is more prevalent among newly diagnosed CCS patients than in controls. Manifestation of pellagra is a less sensitive indicator, and dependence on this endpoint could lead to a lack of appropriate nutritional support for this group of patients.
Shah
Girish M
GM
Laboratory for Skin Cancer Research, CHUL Research Center (CHUQ), Faculty of Medicine, Laval University, Sainte-Foy, Quebec, Canada.
Shah
Rashmi G
RG
Veillette
Helene
H
Kirkland
James B
JB
Pasieka
Janice L
JL
Warner
Richard R P
RR
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002276:Carcinoid Tumor / Q000097:blood* / Q000473:pathology / Q000652:urine; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000097:blood* / Q000473:pathology / Q000652:urine; D006801:Humans; D006897:Hydroxyindoleacetic Acid / Q000652:urine; D008297:Male; D008303:Malignant Carcinoid Syndrome / Q000097:blood* / Q000473:pathology / Q000652:urine; D008875:Middle Aged; D009525:Niacin / Q000172:deficiency*; D012701:Serotonin / Q000097:blood; D014364:Tryptophan / Q000097:blood
D009525:Niacin; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan