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Osteocalcin in human serum: a circadian rhythm
The Journal of Clinical Endocrinology and Metabolism
|April 1, 1985
Summary
Circulating osteocalcin, a bone turnover marker, exhibits significant circadian rhythmicity in healthy adults. Osteocalcin levels peak nocturnally, highlighting the need for timed blood sampling in clinical studies.
Area of Science:
- Endocrinology
- Bone Metabolism
- Clinical Chemistry
Background:
- Osteocalcin is a vitamin K-dependent protein synthesized in bone and present in blood.
- Elevated serum osteocalcin levels are indicative of increased bone turnover rates.
- Understanding osteocalcin's temporal variations is crucial for accurate clinical assessment.
Purpose of the Study:
- To investigate the 24-hour circadian rhythm of serum osteocalcin in healthy adults.
- To determine the pattern of osteocalcin concentration fluctuations over a 24-hour period.
- To assess potential correlations between osteocalcin levels and calcium/phosphate concentrations.
Main Methods:
- Serum osteocalcin was measured every 30 or 60 minutes over 24 hours in 10 healthy adults (6 men, 4 women).
- Blood samples were collected via an indwelling venous catheter.
- Serum levels of ionized calcium, total calcium, and inorganic phosphate were also monitored.
Main Results:
- Circadian rhythmicity in serum osteocalcin was observed in 9 out of 10 individuals.
- Osteocalcin levels decreased in the morning, increased in the afternoon/early evening, and peaked nocturnally.
- No consistent correlations were found between osteocalcin concentrations and serum calcium or phosphate levels.
Conclusions:
- Serum osteocalcin demonstrates a distinct circadian rhythm in healthy individuals.
- The timing of blood collection significantly impacts osteocalcin level measurements.
- Standardizing blood sampling times is essential for reliable clinical investigations of metabolic bone diseases.