The Effect of Parathyroid Hormone on Osseointegration in Insulin-Treated Diabetic Rats.

OBJECTIVES: Uncontrolled diabetes mellitus is associated with impaired osseointegration. Diabetic individuals might benefit from bone anabolic therapies. Intermittent administration of 1-34 parathyroid hormone (PTH) stimulates bone formation in rodent models. However, this anabolic effect fails in diabetic rats. Whether the anabolic effect of PTH can be achieved in insulin-controlled diabetic rats has not been investigated yet. MATERIALS AND METHODS: After diabetes induction with streptozotocin in 40 female Wistar rats, the animals were randomly divided into 4 groups: diabetes, diabetes plus PTH, insulin-treated diabetes, and insulin-treated diabetes plus PTH. After 1 week, miniscrews were inserted in the tibiae. Osmotic pumps with insulin or saline solution were implanted. Animals received 60 mg/kg PTH or saline solution. Histomorphometric analysis was performed. RESULTS: In diabetic rats, no changes of medullary periimplant bone area or bone-to-implant contacts (BICs) were achieved with or without treatment with PTH. However, also animals treated with insulin failed to response significantly to PTH regarding bone area (7.4 +/- 4.1% and 8.1 +/- 4.1%) and BICs (33.7 +/- 16.9% and 49.9 +/- 11.9%). CONCLUSION: These results demonstrate that the metabolic characteristics of the diabetic rats produced a condition unable to respond to PTH treatment, even when hyperglycemia was controlled with insulin.