Colorado State University research points to the use of sheep – instead of laboratory rats – to more accurately study the effects of menopause after several research projects verify that under induced menopause the animal experiences similar symptoms and conditions as do women.
Older ewes – female sheep – experience hot flashes, eye trouble, bone density loss and other symptoms of menopause when their ovaries are removed, which means that research that would benefit menopausal and post-menopausal women, such as research about estrogen replacement therapy, osteoporosis treatments, and prevention of arthritis and sight-inhibiting changes can be conducted on ewes. For example, one Colorado State study that measured hot flashes with tiny embedded temperature loggers in ewes and showed that estrogen replacement results in milder and less frequent hot flashes, a phenomenon previously unreported in other animals with the exception of laboratory rats with their ovaries removed or in research monkeys.
"The accepted animal model to study menopausal symptoms and the occurrence of menopause is a laboratory rat with its ovaries removed, because only humans and primates go into menopause," said Dr. A. Simon Turner, a Colorado State researcher and professor of Veterinary Medicine. "We’ve proven with multiple research projects that sheep can mimic many aspects of menopause in women once their ovaries are removed, which mimics a surgical menopause. The introduction of a large animal model to study body temperature changes and other effects of menopause may prove to be invaluable."
Turner and his colleagues have conducted research on sheep that supports data in human experiments related to menopause. In four separate studies, the group logged hot flashes in ewes, documented the effects of estrogen replacement therapy protecting against eye cataracts, and noted the onset of osteoporosis and changes in cartilage and the occurrence of hormone-caused dry-eye in studies.
"We’ve found that characteristics of menopausal conditions can be reproduced in skeletally mature or aged estrogen-deficient sheep," said Turner. "It’s premature to promote the sheep as the only model to study estrogen deficiency, and the many differences from small animals and non-human primates need to be overcome. This model, however, offers the opportunity to study postmenopausal conditions and the safety and efficacy of new therapeutic agents with some confidence and in an economical way."
Turner has studied osteoporosis and bone density loss in sheep with their ovaries removed and found that the symptoms were very similar to those shown by postmenopausal women. In 1997, in collaboration with Dr. Clint Rubin, State University of New York, Stony Brook, Turner’s research results gained international attention by showing that the bone density in female sheep’s hind legs increased when they were regularly exposed to a metal plate emitting a subtle but high-frequency vibration gained international attention.
Osteoporosis, bone density loss and bone fractures are common among the elderly – experienced by about 20 percent of people older than 70. These fractures are common in hips and are painful and can cause deformity. They’re commonly treated with a combination of medications and supplements including calcium carbonate and estrogen, but treatments usually aren’t preventative.
Hot flashes affect 50 to 80 percent of menopausal women. The incidence of cataracts increases in women as they age, and dramatically so after menopause. Dry-eye, which also effects eye sight, occurs in about 40 percent of menopausal women.