Increased serum calcitonin in pregnancy.

Calcitonin, the hypocalcemic, hypophosphatemic polypeptide hormone of C cell origin, has been reported to be high in pregnant women at delivery. Levels of this hormone were determined by radioimmunoassay in 56 pregnant women in all trimesters and found to be above normal in 72 percent. Values were also increased during the first two days postpartum. Calcitonin levels were not correlated with serum calcium or phosphate, except in the first trimester when levels of this hormone were inversely correlated with serum phosphate. Perhaps the hypercalcitonemia of pregnancy serves to protect the maternal skeleton, while allowing the fetus to accumulate calcium.