Circadian rhythm of urinary calcium excretion during immobilization
Ede, M.C.; Burr, R.G.
Aerospace Medicine 44(5): 495-498
1973
ISSN/ISBN: 0001-9402 PMID: 4710522 Document Number: 68433
Ten healthy men were studied during 2 days of normal activity and from 2 to 4 days of strict bed rest. Excretion of Ca in urine rose during rest, but the increase was not uniformly distributed over each 24 h. Instead the incremental Ca excretion showed a circadian rhythm with 61% excreted between 9 am and 3 pm. A similar pattern of Ca excretion was seen in 4 immobilized patients with recent-onset traumatic paraplegia. Two chronic paraplegics without hypercalciuria did not have such an excretory rhythm. Circadian rhythms of bone resorption seem to account for the observed rhythm of excretion of Ca in urine.