Growth hormone does not enhance the anabolic effect of human parathyroid hormone (1–34) on bone in aging multiparous and virgin rats

Abstract

In humans, the progressive loss in skeletal bone mass with aging increases the risk of osteoporosis and bone fractures in the elderly. As parathyroid hormone (PTH) and growth hormone (GH) may both be anabolic in bone, we tested if the combination of these hormones would increase bone mass more than either agent alone in aging multiparous and virgin female rats. In four separate studies, female rats (15–18 months old) were treated for 12 or 15 days with synthetic human parathyroid hormone (hPTH 1–34) at 80 μg/kg per day given once daily, alone or combined with ovine GH at 1 mg/kg per day given twice daily. Bone of distal femurs, proximal tibias and lumbar vertebrae, dietary mineral (Ca, P, Mg) excretion and balance and serum chemistry were assessed. PTH alone stimulated bone formation and increased bone mass in three of four experiments and consistently increased serum 1,25-dihydroxyvitamin D 3 (1,25-(OH) 2D 3) and mineral retention. GH alone did not change either bone formation or bone mass, but combined with PTH increased mineral retention and serum 1,25-(OH) 2D 3), more than either hormone alone. Despite this stimulatory effect on Ca retention, GH did not further enhance the anabolic effect of hPTH 1–34 on bone mass of aging multiparous and virgin female rats.