Diurnal rhythm in serum osteocalcin: relation with sleep, growth hormone, and PTH(1-84)

We examined the role of sleep, growth hormone (GH), and parathyroid hormone [PTH(1-84)] as regulators of the diurnal rhythm of the osteoblastic bone marker, serum osteocalcin (OC). Nine normal subjects were followed with hourly blood sampling during one 24-hour period with normal sleep pattern, and one 24-hour period with absolute sleep deprivation. We found that the rhythm in serum OC did not exhibit significant changes (P greater than 0.50). Serum OC (mean +/- SE) was 30.9 +/- 2.5 micrograms/liter during sleep (2330-0730 hours) versus 29.9 +/- 4.9 micrograms/liter during sleep deprivation (not significantly different). The serum GH rhythm was significantly different on the two occasions (P less than 0.01). A maximum GH peak (mean +/- SE) of 10.3 +/- 2.4 micrograms/liter occurred at 0136 hours +/- 6 minutes during sleep compared with a maximal peak of 7.6 +/- 1.2 micrograms/liter (P less than 0.01) at 0245 hours +/- 20 minutes (P less than 0.01) during sleep deprivation. During sleep (2330-0730 hours), mean serum GH was 3.61 +/- 0.60 micrograms/liter compared with 2.39 +/- 0.40 micrograms/liter during sleep deprivation (P less than 0.005). Small insignificant changes occurred in serum PTH (1-84) and serum ionized calcium during the two occasions. We conclude that sleep and GH are not acute controlling factors of the diurnal rhythm in serum OC and the role of serum PTH(1-84) remains unsettled.