Oral Presentation 29th Australian and New Zealand Bone and Mineral Society Annual Scientific Meeting 2019

The systemic effect of Parathyroid Hormone and Alendronate on femoral bone volume in the rat ulnar stress fracture model (#15)

Mahmoud M Bakr 1 2 , Nupur Kanwar 1 , Wendy Kelly 2 , Athena Brunt 2 , Bradley C Paterson 2 , Bridie Mulholland 2 , Mark R Forwood 2
  1. School of Dentistry and Oral Health, Griffith University, Gold Coast, Queensland, Australia
  2. School of Medical Science, Griffith University, Gold Coast, Queensland, Australia

Alendronate (ALN), is used to treat osteoporosis, but long-term treatment can lead to side effects such as atypical femoral fractures (AFF). Conversely, intermittent parathyroid hormone (iPTH) increases bone formation. Ulnar SFx was produced in eighty female wistar rats, then treated with either a single iPTH injection, daily iPTH (8 μg/100g/day) for 14 days, or pretreated with ALN (1.0 ug/kg/day) for 14 days and continued ALN throughout the whole experiment, treated with combined ALN-PTH, or vehicle (VEH). Histomorphometric analysis of the proximal femora was performed to determine systemic effects of iPTH. A single injection of iPTH resulted in significant increases in trabecular bone area (Tb.Ar) (P= 0.009), BV/TV (P=1.87 X 10-4), and osteoclast perimeter (Oc.Pm) (P= 0.036) after two weeks, compared to VEH. At six weeks, there was a significant decrease in osteoclast number (N.Oc) (P= 2.84 X 10-4), and Oc.Pm (P= 0.041) in the VEH group, compared to the single iPTH injections. When comparing daily iPTH and a single injection, there was a significant increase in Tb.Ar (P= 0.015), BV/TV (P= 2.8 X10-4), and Oc.Pm (P= 0.008) after two weeks, as well as a significant increase in cortical bone area (Ct.Ar) (P= 0.023), and a significant decrease in Tb.Ar (P= 0.037) at six weeks in the single iPTH group compared to daily iPTH. Combined treatment (ALN-PTH), even with continued ALN, showed comparable results to daily iPTH in terms of their effects on histomorphometric variables. There was a significant increase in Tb.Ar (P= 2.2 X10-4) and Ct.Ar (P= 0.002) after two weeks, a significant increase in N.Oc (P= 6.7 X 10-7), and Oc.Pm (P= 9.2 X10-5) after six weeks in ALN-PTH when compared to ALN. Our results confirm that intermittent PTH has a systemic anabolic response at a distant skeletal site when given post SFx.