Plasma total and ionised calcium, albumin and globulin concentrations in pre- and post-menopausal women and the effects of oestrogen administration.

Abstract

There is a significant increase in the mean fasting plasma total calcium concentration in women at the menopause, accompanied by an increased excretion of calcium in the urine [ 1,2]. These changes are thought to be due to increased resorption following the cessation of ovarian oestrogen production since bone loss can be reduced and plasma and urine calcium levels lowered by the administration of oestrogens [3-91. The increase in plasma total calcium concentration at the menopause could be due to an increase in the concentration of ionised calcium or to changes in the concentration of the plasma proteins or both. A significant increase in the plasma ionised calcium concentration has been reported after oophorectomy or a natural menopause [IO] but it is not known whether the observed increase in plasma total calcium concentration is completely accounted for by this change. Similarly the decrease in plasma total calcium concentration following oestrogen administration could reflect a fall in the concentration of ionised calcium or a change in the concentration of one or more plasma proteins or both. The concentrations of many of the plasma proteins are known to be altered during oestrogen administration and of particular interest in the present context is the decrease in the concentration of albumin [ 11,121 since this is the main cdcium-binding protein in the plasma. The effect of oestrogen administration on plasma ionised calcium levels has not been reported. In an attempt to answer these questions we have examined the plasma total and ionised calcium concentrations and also albumin and globulin concentrations in preand post-menopausal women and in post-menopausal women receiving oestrogens.