To test the hypothesis that Teriparatide injections given 20 micrograms/daily subcutaneously, for one month, are able to produce reliable changes in the bone marker in a severe osteoporotic population

Inclusion Criteria:

• Presents with severe osteoporosis based on the disease diagnostic criteria and upon physician assessment
• Postmenopausal, nonpregnant, women older than 50 years of age, with previous fracture history such as hip, spine, wrist, ribs, clavicle, humerus, tibia, and fibula or men over 50 years of age with low impact fractures (fragility).
• Outpatients without concomitant diseases and with life expectancy of at least 3 years, according to the medical criteria.
• Cannot be on medicines that can disturb bone metabolism.
• Patients should be capable of self-injection, to learn the use of Pen device and are in agreement with its use.

Exclusion Criteria:

• Directly affiliated with the conduct of this study, or are the immediate family of someone directly affiliated with the conduct of this study (that is, Lilly employees, investigators, site personnel, or their immediate families). Immediate family is defined as a spouse, parent, child, or sibling, whether biological or legally adopted.
• Received treatment within the last 30 days with a drug (not including study drug) that has not received regulatory approval for any indication at the time of study entry.
• Previously completed or withdrawn from this study or any other study investigating Teriparatide.
• Secondary osteoporosis or any disease that affects the bone metabolism, as renal osteodystrophy, osteomalacia, hypoparathyroidism, and hyperparathyroidism, and intestinal malabsorption.
• Cancer history in the 5 years prior to visit 1, with exemption of basocellular carcinoma treated and cervix carcinoma definitively treated at least 1 year before to visit 1