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)2 vitamin D or to intestinal resistance to its action, rather than directly to the low circulating estrogen that results following menopause. The studies presented indicate that the intestinal mucosal cells of rats contain estrogen receptor immunoreactivity, express the mRNA for estrogen receptors, and respond directly to 17 beta-estradiol with enhanced calcium transport that is suppressed by gene transcription and protein synthesis inhibitors. These findings suggest that estrogen has a physiological role in the regulation of intestinal calcium absorption and that its deficiency in postmenopausal osteoporosis, and following therapeutic oophorectomy, may result directly in calcium malabsorption that is believed to be an important factor in the bone loss that occurs in these conditions.