title: Should food intake and circadian rhythm be considered when measuring serum calcitonin level?
abstract: OBJECTIVE
  To investigate the relationship between both food intake and circadian rhythmicity and serum calcitonin in the same individuals.
  
  
  METHODS
  Eighteen healthy subjects, 10 males and 8 females, aged 22 to 24 years, were recruited. Serum calcitonin level was measured three times: at 0800 after a 9-hour overnight fast, at 0900 postprandially, and at 1700 after another 9-hour fast. The same protocol was repeated once.
  
  
  RESULTS
  The mean calcitonin levels (at 0800) were 3.92 pg/mL (SD, 2.5 pg/mL) on Day 1 and 3.52 pg/mL (SD, 2.1 pg/mL) on Day 2. Mean postprandial calcitonin (at 0900) was 9.46 pg/mL (SD, 8.6 pg/mL) on Day 1 and 9.91 pg/mL (SD, 6.9 pg/mL) on Day 2. Mean fasting calcitonin in the evening (at 1700) was 6.74 pg/mL (SD, 4.73 pg/mL) on Day 1 and 6.49 pg/mL (SD, 3.57 pg/mL) on Day 2. There was no significant difference in the mean calcitonin level on days 1 and 2 for any of the three time points examined. Statistically significant differences were found between postprandial and evening calcitonin levels and the fasting levels on Day 1 (P = .018 and .015, respectively) and Day 2 (P = .001 and .0009, respectively).
  
  
  CONCLUSIONS
  These results suggest that serum calcitonin level is significantly influenced by food intake in healthy young subjects and reveal a circadian rhythm, with increased calcitonin level during the afternoon. The timing of blood sampling relative to meals should be integrated into clinical practice and research settings involving serum calcitonin measurements.
authors: Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, The University of Jordan, Jordan University Hospital, Jordan.
authors: Ayman A
authors: AA
authors: Zayed
authors: Mohammed
authors: M
authors: Alzubaidi
authors: Sama
authors: S
authors: Atallah
authors: Munther S
authors: MS
authors: Momani
authors: Wael K
authors: WK
authors: Al-Delaimy
mesh_terms: D000328:Adult; D002116:Calcitonin / Q000097:blood*; D002940:Circadian Rhythm / Q000502:physiology*; D004435:Eating / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D055815:Young Adult
chemical_list: D002116:Calcitonin