Calcium supplementation and parathyroid hormone

Abstract:

In eight healthy female volunteers 18–19 years of age, the effect of 600 mg/day calcium (Ca) supplementation as milk (milk group) or active absorbable algal Ca (AAACa) (AAACa group) was studied for 1 week by a crossover method. Ca, phosphorus (P), magnesium (Mg), osteocalcin, parathyroid hormone (PTH), and markers of bone metabolism in serum or first morning urine samples were measured. Serum and urine Ca and Mg increased slightly in both groups, and urinary excretion of markers of bone resorption decreased in both groups to a similar extent, whereas serum PTH decreased significantly only in the AAACa group with on accompanying rise in serum P and fall in urine P. Higher biological availability of Ca from AAACa than from milk may explain the more efficient suppression of PTH by AAACa than by milk. The higher P content in milk may have stimulated PTH secretion, interfering with the suppression by Ca that would have otherwise occurred..