Estrogen‐induced osteoid formation in the osteon of mature female rabbits. An electron‐microscopic study

The osteons of mature female rabbits injected with estradiol valerate, parathyroid extract, or a combination of both were studied. Two, 1 mg injections of estradiol valerate (Delestrogen®) given in a one week period stimulated osteoid production on the inside of the lacunar borders of osteocytes but had little effect on osteoid production along the perimeter of the Haversian canal. Parathyroid hormone induced osteolysis after two weeks of treatments, with little apparent increase in osteoclast numbers. Parathyroid extract treatment for one week followed by estradiol valerate treatment in combination with parathyroid extract treatment the second week induced osteoid formation along both lacunar borders and Haversian canal perimeters. This evidence shows that estrogen can stimulate osteoid production and is not limited to inhibition of bone resorption. Increased osteoid production along the perimeter of the Haversian canal in dual‐treated rabbits implies an interaction between estrogen and parathyroid hormone.