A circadian variation in serum calcium, albumin and PTH concentration in normal subjects has been demonstrated. The levels of the three blood constituents were remarkably constant during the day, but striking night and early morning changes occurred. Serum calcium levels were highest at 8:00 p.m. and reached a nadir between 2:00 and 4:00 a.m. Serum albumin levels were parallel to those of serum calcium. PTH levels began to rise after 8:00 p.m., reached the highest levels between 2:00 and 4:00 a.m., and fell to baseline values by 8:00 a.m. The nocturnal fall in serum calcium levels appears to be secondary to dilution of serum proteins by increasing blood volume. The nocturnal rise in PTH levels appears to be independent of serum calcium levels within the normal range but it can be abolished by induced hypercalcemia.
William Jubiz, Janet M. Canterbury, Eric Reiss, Frank H. Tyler
Usage data is cumulative from August 2023 through August 2024.
Usage | JCI | PMC |
---|---|---|
Text version | 704 | 0 |
133 | 150 | |
Scanned page | 421 | 436 |
Citation downloads | 60 | 0 |
Totals | 1,318 | 586 |
Total Views | 1,904 |
Usage information is collected from two different sources: this site (JCI) and Pubmed Central (PMC). JCI information (compiled daily) shows human readership based on methods we employ to screen out robotic usage. PMC information (aggregated monthly) is also similarly screened of robotic usage.
Various methods are used to distinguish robotic usage. For example, Google automatically scans articles to add to its search index and identifies itself as robotic; other services might not clearly identify themselves as robotic, or they are new or unknown as robotic. Because this activity can be misinterpreted as human readership, data may be re-processed periodically to reflect an improved understanding of robotic activity. Because of these factors, readers should consider usage information illustrative but subject to change.