This study will test in several innovative ways, several different combinations of PTH and oral monthly ibandronate for the treatment of osteoporosis in postmenopausal women. The intension is to provide other options for treatment than the current standard 2 year course of drug therapy. These options may lead to treatment where the two years of therapy are spread over several years.

This randomized double-blind clinical trial for the treatment of postmenopausal osteoporosis will be conducted and coordinated by study investigators who also participated in the investigator-initiated PaTH study. Final data analysis will compare the results from this trial with those from the PaTH study. In the PaTH study, 238 women between 55 and 85 years of age were randomized to receive either:

1. PTH for 1 year followed by alendronate for 1 year
2. PTH and alendronate for 1 year followed by alendronate for 1 year
3. alendronate for 2 years
4. PTH for 1 year followed by placebo for 1 year.

In the PICS 44 postmenopausal women between the ages of 55 to 75 years of age with osteoporosis who meet the inclusion/exclusion criteria,will be randomized to the following 2 treatment groups. Group A will received 6 months of monthly Ibandronate, plus daily PTH 1-84,100 μg; followed by 18 months of Ibandronate only. Group B will received 3 months of daily PTH 1-84,100 μg; followed by 9 months of monthly Ibandronate, over 2 years. Calcium (400-650 mg) and Vitamin D (400 IU) supplements will be provided to all participants.

The primary objective is to determine if, at 3 months, the women treated with the concurrent combination of PTH and ibandronate (Group A) show a significant increase in bone marker formation compared to baseline (unlike the combination PTH/alendronate-treated women in PaTH). This will be accessed by examining the change in the markers P1NP, BSAP and serum CTX.

As a secondary objective, we will compare the trabecular spine BMD measures of those treated with concurrent PTH/Ibandronate (Group A) to those who received 3 months of PTH followed by Ibandronate(Group B). Another secondary objective will be to compare changes between groups in trabecular bone and DXA spine BMD after 2 years of treatment.

Changes to the fat content of the vertebrae during a course of PTH therapy will be examined using MRI spinal spectroscopy. Crosstabulation of these changes against changes in trabecular BMD, should indicate an effect on measurements. As well, the effect of a second three-month course of PTH therapy in Group B is of major interest.

Inclusion Criteria:

• Female
• Aged 55-75 years, inclusive, at randomization
• Postmenopausal for >= 5 years (no menses for at least 5 years)
• Have an evaluable bone mineral density scan (DXA) at the spine AND at the hip with a T-score <= -1.5 either at the spine or the femoral neck or total hip OR have a T-score <= -1.0 with at least one of the following risk factors for fracture: 1)Age >= 65 years; 2)History of post-menopausal fracture (non-vertebral or vertebral); 3)Maternal history of hip fracture.
• Be willing and able to self-administer daily injections
• Signed written consent form.

Exclusion Criteria:

• History of more than 12 months of oral bisphosphonate use ever, or any use (>4 weeks) with the past 12 months. For those with 4 weeks to 12 months of previous use, a 24 month washout is required.
• History of any IV bisphosphonate use.
• History of more than 12 month of PTH use ever, or any use (>4 weeks) with the past 12 months.
• History of estrogen (oral or patch) more than one month in the last 6 months or for more than 12 months in the last 2 years.
• Have type 1 or uncontrolled type 2 diabetes mellitus (defined as hemoglobin A1C > 10.0), or currently using insulin.
• Have serum calcium >10.2 mg/dl.
• Have Vitamin D level <15 nanograms/ml.
• Have Stage III renal insufficiency where calculated creatinine clearance < 40 ml/min by MDRD.
• Have any history of kidney stones in the last 10 years.
• Have any history of hypercalcuria or currently have urine calcium >300 mg/24 hours.
• Have any history of hypercalcemia.
• Have any history of sarcoidosis.
• Have any history of hyperparathyroidism.
• Have any history of active or treated tuberculosis or other granulomatous disorders.
• History of breast cancer, melanoma or hematologic malignancy which has required treatment within the last 10 years.
• Any history of bone cancer or Paget's disease of bone
• Any other metabolic bone disease which has required treatment within the last 10 years.
• History of any other non-skin cancer which has required treatment within the last 10 years.
• Have a documented history of symptomatic esophageal reflux, achalasia or esophageal stricture.
• Be currently taking > 7.5 mg systemic prednisone or equivalent per day or for more than 10 days in the last 3 months.
• Be currently using > 2 puffs, 4 times / day of inhaled steroids.
• Be currently taking anticoagulants.
• Be currently taking anticonvulsants that alter hepatic vitamin D clearance
• Have used Calcitonin within the past 3 months.
• Have used Raloxifene in the last 6 months or for more than 12 months in the last 2 years.
• Have used Tamoxifen in the last 6 months or for more than 12 months in the last 2 years.
• Have used fluoride for at least a month within the past 5 years.
• Be currently taking > 1000 IU/day Vitamin D
• Using Vitamin D analogues or metabolites.
• Be currently taking thyroid hormone replacement AND have a TSH < 0.1mIU/L.
• Have any major life-threatening illness.
• Concurrent enrollment in another double-blinded clinical treatment intervention study.
• Life expectancy less than 3 years
• Willing to discontinue all over the counter nutritional supplements

Adverse event data was collected for the duration of the study (2 years) for each participant.