Long-term benefits and risks of parathyroid hormone treatment in compliant osteoporotic patients. A Danish national register based cohort study

Anne-Luise Thorsteinsson, Louise Hansen, Peter Vestergaard, Pia Eiken

Medical treatment of osteoporosis should preferably be both effective and have minimal side effects. The aim of the present study was to examine long-term benefits and risks of parathyroid hormone (PTH) treatment in compliant patients. This is a nationwide retrospective cohort study based on national registers in which we identified 1739 patients treated with PTH (2003-2010) (index cases) for at least 18 months and with a medication possession rate of > 0.8. For comparison, patients treated with bisphosphonate (BP) (n = 13,131) and anti-osteoporotic treatment-naïve controls (n = 12,721) were selected. Incidence of fractures, drug consumption, and comorbidity were compared between the three cohorts. Mean follow-up of the PTH-treated patients was 4.3 years (range 1.8-8.7 years). Before initiation of treatment, PTH patients had a significantly higher Charlson comorbidity index score and more osteoporotic fractures than both BP patients and controls. No difference was detected in the incidence of fractures during PTH treatment or years after between PTH patients and BP patients. No significant difference in the use of drugs was seen between PTH and BP patients, except for PPI intake which was higher in PTH patients. No significant increases were found in the incidence of cancers or other ICD-10 diagnoses among PTH-treated patients in comparison with both BP and controls. Overall, PTH treatment is effective and safe. Following PTH treatment in compliant patients, neither fracture incidence nor drug consumption differed between PTH-treated and BP-treated patients, despite the fact that PTH-treated patients had more severe osteoporosis. No increased incidence of malignant diseases or other diseases was detected.