Re: must be my timing...

involuntarily~

http://www.ncbi.nlm.nih.gov/pubmed


1. J Clin Endocrinol Metab. 2000 Apr;85(4):1367-9.

Urinary Iodine concentration follows a circadian rhythm: a study with 3023 spot
urine samples in adults and children.

Als C, Helbling A, Peter K, Haldimann M, Zimmerli B, Gerber H.

Division of Clinical Chemistry, Inselspital, University of Bern, Switzerland.

Our overall aim is to monitor Iodine supply in a prospective study before and
after the September 1998 increase of salt Iodide content in Switzerland. Because
iodide is supplied by alimentation, we moreover wondered whether urinary iodine
concentration (UI) is governed by circadian rhythmicity. Forty-two subjects (18
males and 24 females, including 13 children) collected 3023 urine spots between
May 1996 and May 1998, at a rate of three to five samples per month, at any time
of the day. The results show that circadian rhythmicity of UI in adults and
children was found independent of the individual subject, age, gender, and
season. Lowest UI levels were found between 8-11 h. A curve increasing
progressively between 12 and 24 h was obtained. UI returned to base-line levels
between 21 and 22 h in children only. UI peaks occurred 4-5 h after main meals;
children's peaks occurred later than that of adults. Although the existence of a
circadian rhythm of UI is probably universal, its profile, however, depends on
alimentation. Because nadir of UI is represented by morning spots, this might
seem an appropriate collecting period. In view of the significant circadian
rhythmicity of UI, studies with restriction of sampling time to morning hours,
for example, cannot be directly compared with studies in which urine is sampled
all over the day.


PMID: 10770167 [PubMed - indexed for MEDLINE]
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