Nonhuman Primate Models of Menopause (Part 17)
Rhesus monkey. Several recent studies have begun to address these concerns. One study examined 178 female rhesus monkeys aged 2-34 yr. No evidence of change with age in total body and spine density was reported; however, small but significant reductions of bone mineral density (BMD) in radial sites were seen. The second study utilized 58 female rhesus monkeys aged 4-30 yr and reported reduced bone mass in older postmenopausal monkeys at the total body, spine, and distal radius sites. Another study reported slight but significant reductions in lumbar vertebrae BMD from 131 female rhesus skeletons aged 17-22 yr. Finally, a study in 20 premenopausal rhesus monkeys aged 8-23 yr reported a significant age-associated bone loss at two radial sites, estimated at less than 5% per year in monkeys that reached peak bone mass, but not for total body or spine bone mass. The influence on bone remodeling of the approximately 10-fold larger amounts of calcium and vitamin D, and of the soy-based diet containing phytoestrogens, in monkey chow relative to the average human diet is unknown. canadian neighbor pharmacy online
These data support a slight reduction in bone mass in females between the ages of peak bone mass and menopause. Thus, rhesus monkeys may represent a valuable model of human age-dependent bone loss. A major concern, however, is that unlike humans, female rhesus monkeys apparently do not lose significant vertebral bone mass before menopause. Whether the rate of bone loss accelerates after menopause in female rhesus monkeys is not known. Thus, additional studies of the peri- and postmenopause conditions are needed.
Cynomolgus monkey. Bone loss in cynomolgus monkeys occurred only when the animals were ovariectomized after reaching peak bone mass (~12 yr of age). Cortical bone remodeling was stimulated by ovariectomy and decreased by estrogen treatment. Initiating hormone replacement, even 2 yr following ovariectomy, protected against bone loss.