Effect of menopause and aging on serum total and ionized calcium and protein concentrations

The effects of menopause and aging on serum total and ionized calcium concentrations were evaluated in 402 healthy women (aged 18-71 years), of whom 83 were premenopausal and 319 postmenopausal. Serum albumin and globulin concentrations and serum pH were also measured in most of these women. Serum total but not ionized calcium concentration increased significantly at menopause. This increase in the protein-bound component of total calcium in postmenopausal women was associated with increases in mean serum globulin concentration (P = 0.03) and in serum pH (P = 0.03). Serum total calcium declined with age within the pre- and postmenopausal groups (r = -0.225, P = 0.04 and r = -0.121, P = 0.03, respectively). This was associated with an age-related decrease in serum albumin concentration in all women (r = -0.47, P less than 0.0001). Neither serum globulin concentration or pH varied with age. Thus, menopause and aging affect serum total, but not ionized calcium concentration.