Growth Hormone Cannot Enhance the Recovery of Dexamethasone-Induced Osteopenia after Withdrawal in Young Female Wistar Rats

Abstract

Dexamethasone (DEX) suppresses the secretion of and responsiveness to growth hormone (GH). Here we aimed to assess the therapeutic effects of GH on the DEX-induced osteopenia. Female Wistar rats were treated for 2 weeks with DEX (200 μg/day) or saline as a control. DEX significantly decreased body weight gain, bone mineral density (BMD), growth plate thickness, area ratio of trabecular bone, and serum osteocalcin levels. DEX also elongated the tibia primary spongiosa and caused many tiny lipid droplets in the tibia marrow. These results indicated that DEX induced osteopenia in rats. We then assessed the effects of GH on the recovery of osteopenia after withdrawal of DEX. DEX-treated rats were subsequently treated for 1 week with GH (0.1 or 0.3 U/day) or saline, while saline-pretreated rats were treated for 1 week with saline as a control. GH (0.1 or 0.3 U/day)-treated rats showed a catch-up growth in various bone measurements by one week after DEX withdrawal, though most of them remained subnormal. GH treatment did not enhance the recovery of DEX-induced osteopenia. Therefore a short-term exposure to DEX significantly impaired the bone metabolism, which started to recover soon after withdrawal of DEX. Unfortunately, immediate administration of GH after withdrawal of DEX did not enhance the recovery process.