[Calcium homeostasis in pregnancy and lactation].

The daily required dose of calcium is greatly increased during pregnancy. It is caused by the transition of about 30 g to the fetus and by enhanced urinary excretion. The normal calcium homeostasis is maintained by parathormone (PTH), calcitriol and PTH-related peptide (PTHrP). The concentration of calcitriol is augmented as well as the absorptive surface of the gut. PTHrP is involved in the regulation of placental calcium transport and also in lactation and initiation of labor. Bone turnover is enhanced during pregnancy and sometimes may evoke osteoporosis, especially in bones which form the hip joint. After delivery, in some cases osteoporosis may be found in vertebral column, whilst during lactation in long bones. The role of heparin in the pathogenesis of osteoporosis is also mentioned.