Differential Effects of Growth Hormone and Alfa Calcidol on Trabecular and Cortical Bones in Hypophysectomized Rats (Publication with Expression of Concern)

Growth hormone (CH) deficiency in children causes severe growth retardation. vitamin D deficiency, and osteopenia. We investigated whether alfacalcidol (IOHD) alone or in combination with GH can improve bone formation. Forty hypophysectomized female rats (HX) at the age of 8 wk were divided into HX, HX + IOHD (oral 0.25 mu g/kg daily), HX+GH (0.666 mg/0.2 mL SC daily) and HX + GH + IOHD groups for a 4-wk study. Results showed that GH increased body weight. bone area, bone mineral content (BMC). and bone mineral density (BMD), whereas IOHD only increased BMC and BMD. In cortical bone. GH increased both periosteal and endocortical bone formation resulting in a significant increase in cortical size and area in percentage, whereas IOHD suppressed endocortical erosion surface per bone surface (ES/BS) without a significant effect on bone formation rate per bone Surface (BFR/BS). In trabecular bone, GH mitigated the bone loss by increasing BFR/BS, whereas the IOHD effect was by suppression of trabecular bone turnover in the HX rats. The combination of GH and IOHD had no additive effect on increasing trabecular bone mass. In conclusion. GH activates new bone formation and increases bone turnover whereas IOHD suppresses bone turnover. The combination intervention does not seem to provide any additive benefit. (Pediatr Res 65: 403-408, 2009)