Jubiz W, Canterbury J M, Reiss E, Tyler F H
J Clin Invest. 1972 Aug;51(8):2040-6. doi: 10.1172/JCI107010.
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. Serum phosphate levels were lowest between 8:00 a.m. and 10:00 a.m. and highest between 2:00 a.m. and 4:00 a.m. The data presented suggest that circadian changes in serum phosphate levels are not mediated in toto by parathyroid hormone but they are exaggerated when the secretion of this hormone is inhibited. They are independent of growth hormone levels and activity but they are greatly modified during a prolonged fast.
正常受试者血清钙、白蛋白和甲状旁腺激素（PTH）浓度存在昼夜节律变化。这三种血液成分的水平在白天相当稳定，但在夜间和清晨出现显著变化。血清钙水平在晚上8点最高，在凌晨2点至4点之间降至最低点。血清白蛋白水平与血清钙水平平行。PTH水平在晚上8点后开始上升，在凌晨2点至4点之间达到最高水平，并在上午8点降至基线值。血清钙水平的夜间下降似乎是由于血容量增加导致血清蛋白稀释所致。PTH水平的夜间升高似乎在正常范围内与血清钙水平无关，但可通过诱导高钙血症消除。血清磷酸盐水平在上午8点至10点之间最低，在凌晨2点至4点之间最高。所呈现的数据表明，血清磷酸盐水平的昼夜变化并非完全由甲状旁腺激素介导，但当该激素的分泌受到抑制时，这种变化会被夸大。它们与生长激素水平和活性无关，但在长期禁食期间会发生很大改变。
