Because of these limitations, young ovariectomized cy-nomolgus monkeys are currently being used as a model to study the effects of hormonal manipulation on hypothalamic neuropeptide gene expression. This model has the advantages of removing the confounding influence of age and of allowing hormone replacement in regimens that mimic those given to postmenopausal women. These studies in monkeys also have obvious advantages compared with human studies. Invasive studies permit access to brain tissue to explore effects in the brain associated with loss of estrogen, either through natural menopause or via ovariectomy, and subsequent replacement of estrogen. Studies using brain tissue from ovariectomized cynomolgus monkeys suggest that neurokinin B mRNA, which is observed to be present in hypertrophied neurons of the infundibular nucleus in human autopsy specimens from postmenopausal women, was repressed by estrogen in the monkeys. canadian health & care mall
In contrast, in the same study, no effect of ovariectomy and estrogen replacement was observed on POMC neurons in the infundibular nucleus, suggesting lack of regulation by estrogen.
An unanswered question that needs further study is the suitability of the ovariectomized young monkey as a model for the postmenopausal human. Although the ultimate result of both normal menopause and surgical menopause is the same (i.e., cessation of menstrual cycles and infertility), the repercussions on a woman’s health may differ because of age and rate of loss of estradiol and other ovarian hormonal factors. Hence, changes in reproductive hormones may result in a broader spectrum of effects in an older individual than when they occur in a younger woman who is experiencing fewer age-related changes in other systems.