EVIDENCE FOR ESTROGEN RECEPTOR-LINKED CALCIUM-TRANSPORT IN THE INTESTINE

Intestinal calcium malabsorption in postmenopausal osteoporotic women is often linked indirectly to decreased serum 1,25(OH)2vitamin D or to intestinal resistance to its action, rather than directly to the low circulating estrogen that results following menopause. The studies pre sented indicate that the intestinal mucosal cells of rats contain estr ogen receptor immunoreactivity, express the mRNA for estrogen receptor s, and respond directly to 17beta-estradiol with enhanced calcium tran sport that is suppressed by gene transcription and protein synthesis i nhibitors. These findings suggest that estrogen has a physiological ro le in the regulation of intestinal calcium absorption and that its def iciency in postmenopausal osteoporosis, and following therapeutic ooph orectomy, may result directly in calcium malabsorption that is believe d to be an important factor in the bone loss that occurs in these cond itions.