A physiological role for calcitonin: protection of the maternal skeleton.

Plasma-calcitonin levels, measured with an established and reliable extraction radioimmunoassay technique, were significantly higher throughout normal pregnancy and lactation than in normal non-pregnant women, and were not immediately influenced by the acute stimulation of breast-feeding. Thus, more calcitonin circulates at times of physiologically increased calcium need. It is suggested that an important function of calcitonin is the protection of the healthy maternal skeleton from excessive resorption by opposing the resorptive action of 1,25-dihydroxycholecalciferol on bone.