This study will directly compare the effect of placebo and escalating doses of PTHrP given subcutaneously to postmenopausal women for three weeks. Each subject will have four outpatient visits and one inpatient 24-hour visit on the last day. 20 women in phase I will receive either placebo or 500 micrograms/day of PTHrP. 500 micrograms/day was selected as the lowest dose because it is similar to the dose used in our previous 3 month placebo controlled study. In Phase II, the doses of PTHrP will be increased in increments of approximately 30% for each successive group, i.e., 750, 1000, 1250, and 1500 micrograms. After the first group of 10 successfully receives 500 micrograms/day for 21 days, increased doses will be given to groups of three subjects until evidence of dose limiting toxicity (DLT) occurs, or a maximum dose of 1,500 micrograms is reached. Dose limiting toxicities are specified in the protocol and comprise either one major criteria: hypotension, orthostatic hypotension, tachycardia, hypertension, hypercalcemia or hypophosphatemia; or two minor criteria: flushing, nausea/vomiting, abdominal or muscle cramps, dizziness/lightheadedness, palpitations, or any other unpleasant subjective symptom.