Enticingly, intermittent treatment of a breast cancer mouse model with PTH (teriparatide) was shown to reduce the incidence of spontaneous bone metastasis to the hind limbs, with no change in extraskeletal metastases to the liver, lungs, or spleen when administered as a pretreatment or initiated 24 h after tumor inoculation [70]; however, a second study found an increase in breast cancer skeletal metastases to the forelimbs and ribs, but no change in dissemination to the hind limbs, following PTH pretreatment [71]. This evidence concerns the gene PTH and breast carcinoma.