The effect of prolactin itself and in combination with estrogen on bone mineral density in female rats.

Estrogen deficiency induced by hyperprolactinemia can reduce bone mineral density. Hyperprolactinemia through other mechanisms other than estrogen deficiency, with direct effect on the bone might cause bone loss in women. The present study evaluated the effect of prolactin itself and in combination with estrogen on bone mineral density of female rats. This study was performed on 50 adult female rats divided into five groups; included (a) Sham, (b) Ovariectomized rats; and (c-e) included ovariectomized rats were given prolactin alone, prolactin + estradiol and estradiol, respectively. Bone mineral density (BMD) and vitamin D metabolism parameters were checked in all groups before and after the study. There was no significant difference in baseline values of these parameters. Estradiol could increase 1,25(OH)2D3 and PTH levels and decrease serum ALP level. In addition, Prolactin could increase serum 1,25(OH)2D3 and ALP levels and decrease tibia BMD significantly without any change in PTH level. Combination of estradiol and prolactin could increase serum 1,25(OH)2D3 and PTH and tibia BMD compared with OVX group. Combination of estradiol and prolactin could significantly increase tibia BMD, in ovariectomized rats. We hypothesized that this combination could improve bone loss secondary to hyperprolactinemia by elevated PTH.