Does Calcitonin Increase During Pregnancy?
Calcitonin levels are increased during pregnancy in most women, with approximately 72% showing elevated levels above normal ranges, though the clinical significance of this elevation remains uncertain. 1
Evidence for Calcitonin Elevation
The research evidence demonstrates that calcitonin increases during pregnancy:
- Calcitonin levels are elevated in approximately 72% of pregnant women across all trimesters, with values remaining increased during the first two days postpartum 1
- Both calcitonin and 1,25-dihydroxyvitamin D are increased during pregnancy and lactation, potentially playing a role in maternal calcium transfer to the fetus and prevention of maternal bone loss 2
- The incremental calcitonin response to provocative stimuli is greater during pregnancy than postpartum and tends to increase with advancing gestation 3
Contradictory Evidence
However, one high-quality longitudinal study challenges this consensus:
- A carefully selected cohort of healthy pregnant women meeting strict optimality criteria showed no significant changes in total calcitonin, extractable calcitonin, or katacalcin levels throughout pregnancy 4
- This study concluded that thyroidal C-cell secretion is not increased during pregnancy and that calcitonin is not involved in mineral homeostasis modifications during pregnancy 4
Physiological Context
The role of calcitonin in pregnancy remains unclear:
- Blood calcium is tightly regulated by parathyroid hormone, calcitonin, and 1,25-dihydroxyvitamin D, with the primary homeostatic mechanism being bone deposition or release 5
- Calcitonin secretion is stimulated by increases in serum calcium concentration and protects against hypercalcemia 2
- The hypercalcitonemia of pregnancy may serve to protect the maternal skeleton while allowing the fetus to accumulate calcium 1
- Enhanced intestinal calcium absorption and renal calcium conservation maintain maternal serum calcium within normal limits despite transferring approximately 30g of calcium to the fetus during gestation 5
Clinical Implications
Despite the physiological changes:
- Calcitonin levels do not correlate with serum calcium or phosphate during pregnancy, except in the first trimester when levels are inversely correlated with serum phosphate 1
- No bone or other abnormalities have been described in states of calcitonin deficiency or excess 2
- The precise role for calcitonin remains elusive more than 50 years after its discovery 2
Important Caveats
- The discrepancy between studies may reflect differences in patient selection criteria, with the negative study using strict optimality criteria that may not represent the general pregnant population 4
- Calcitonin measurement is not routinely recommended during pregnancy for clinical management 5
- The physiological elevation, when present, appears to be an adaptive mechanism rather than a pathological finding requiring intervention 1, 3