Changes in sex hormones and calcium regulating hormones with reference to bone mass associated with aging

Measurement of bone mineral content (BMC), intestinal 47Ca absorption, and calcium regulating hormones and sex steroids in serum were performed on 32 healthy aged subjects and 26 control young subjects. In BMC, there was a progressive fall after age 40, with the rate of decrease being greater in women than in men. A significant correlation was observed between BMC and testosterone in the men and between estrogens and BMC in the women, suggesting the possible importance of testosterone in men and estrogens in women in maintaining bone mass. Plasma PTH showed no change with age. However, the reserve capacity of the parathyroid was significantly reduced in the aged women. Serum levels of ionized calcium were low in aged subjects, indicating a possible alteration with age in the feedback control between ionized calcium levels and parathyroid hormone secretion. C-cell funtion was also decreased with age. Plasma 1,25-(OH)2D and 47Ca absorption tended to decrease with age. Age-related bone loss could be a reflection of the interaction of these hormonal imbalance occurring with age.