Calcitonin levels in sera of infants and children: relations to age and periods of bone growth.

Serum calcitonin levels have been reported to be elevated in premature and newborn infants, a period of maximal rate of bone growth. To determine whether calcitonin remains elevated during the first year of life, a time of rapid extrauterine bone growth, fasting serum calcitonin levels were determined in 31 hospitalized infants and children ages 24 weeks gestation to 6 years. Calcitonin levels were significantly higher in the premature and newborn infants than in the first year of life. However, calcitonin levels in the first year of life were still significantly higher than during the second to sixth years. This fall in serum calcitonin levels parallels the age-related decline in rate of bone growth. One can speculate that the changes in serum calcitonin levels during the first year of life may indicate that it plays a role in bone growth or mineralization. However, the possibility that the changes in calcitonin levels are unrelated to changes in bone growth or mineralization has not been ruled out.