The primary objective of this study is to demonstrate a reduction in the proportion of new vertebral fractures in postmenopausal women with osteoporosis following 3-years of treatment with 20 and 40 mcg/day of teriparatide plus calcium and vitamin D compared with calcium and vitamin D alone.

Inclusion Criteria:

• Ambulatory, postmenopausal women.
• A minimum of either one moderate or two mild atraumatic vertebral fractures, and a minimum of seven evaluable nonfractured vertebrae.
• Hip BMD or lumbar spine BMD measurement at least 1.0 standard deviation (SD) below the average bone mass for young, healthy women (T-score) only in patients with fewer than two moderate fractures or in patients previously treated with therapeutic doses of bisphosphonates or fluorides
• Normal or clinically nonsignificant abnormal laboratory values (serum calcium, PTH(1-84), & urine calcium must be within normal limits at baseline; 25-hydroxyvitamin D must be between the lower limit of normal & 3 times the upper limit of normal at baseline).

Exclusion Criteria:

• Fractures in areas of bone affected by diseases other than osteoporosis (for example, cancer or Paget's disease).
• Satisfactory baseline thoracic and lumbar spinal x-ray views cannot be obtained as determined by the centralized x-ray quality assurance center (for example, severe scoliosis or kyphosis).
• Current or recent (within 1 year prior to randomization) metabolic bone disorders other than postmenopausal osteoporosis, such as Paget's disease, renal osteodystrophy, osteomalacia, or any secondary causes of osteoporosis
• Current or recent (within 1 year prior to randomization) disease which affects bone metabolism, such as hypoparathyroidism, hyperparathyroidism, or hyperthyroidism.
• Currently suspected carcinoma or history of carcinoma in the 5 years prior to randomization.
• Nephrolithiasis or urolithiasis in the 2 years prior to randomization.
• Current or recent (within 1 year prior to randomization) sprue, inflammatory bowel disease, or malabsorption syndrome, or any indication of poor intestinal absorption of calcium, such as the combination of a low urinary calcium excretion and an elevated serum intact parathyroid hormone level.
• Poor medical or psychiatric risk for treatment with an investigational drug, in the opinion of the investigator.
• Treatment with androgens or other anabolic steroids in the 6 months prior to randomization.
• Treatment with calcitonins in the 2 months prior to randomization.
• Treatment with estrogen
• Treatment with progestins in the 3 calendar months prior to randomization, or for more than 2 months in the 12 calendar months prior to randomization.
• Treatment with corticosteroids.
• Treatment with fluorides in the 6 months prior to randomization or for more than 60 days in the 24 months prior to randomization.
• Treatment with oral bisphosphonates in the 3 months prior to randomization or for more than 60 days in the 24 months prior to randomization; treatment with intravenous bisphosphonates in the 24 months prior to randomization.
• Treatment with vitamin D >50,000 IU/week, or with any dose of calcitriol, analogs, or agonists in the 6 months prior to randomization. The 25-hydroxyvitamin D laboratory value at randomization must be between the lower limit of normal and three times the upper limit of normal.
• Treatment with coumarins and indandione derivatives in the 3 months prior to randomization; treatment with heparins >10,000 U/day for more than 30 days in the 6 months prior to randomization.
• Treatment with calcium- or aluminum-containing antacids
• Treatment with any other drug known to affect bone metabolism in the 6 months prior to randomization.
• Treatment with any investigational drug during the month prior to the calcium and vitamin D run-in phase. Treatment with investigational drugs in certain therapeutic classes during the month prior to the calcium & vitamin D run-in phase.