GROWTH-HORMONE IS NOT ABLE TO COUNTERACT OSTEOPENIA OF RAT CORTICAL BONE INDUCED BY GLUCOCORTICOID WITH PROTRACTED EFFECT

Osteopenia and inhibited longitudinal growth in childhood are serious side effects during glucocorticoid therapy, The effects of glucocortic oids on bone have been confirmed in animal experiments, Long-term gluc ocorticoid administration to rats results in reduced body weights, red uced bone growth (length and cross-sectional area), and bone strength, Glucocorticoid treatment also resulted in a reduced bending stress, i ndicating reduced bone quality, Growth hormone, on the other hand, inc reased body weights, bone dimensions, and bone strength, The aim of th e present study was to evaluate if growth hormone administration would have an anabolic effect on rat bone when given to animals also receiv ing a high dosage of glucocorticoid. Five groups of female rats, 3.5 m onths old, were treated as follows: (1) saline control; (2) glucocorti coid (prednisolone: Delcortol 5 mg/kg/day); (3) growth hormone (recomb inant human growth hormone 5 mg/kg/day); (4) glucocorticoid and growth hormone; and (5) food restriction, consisting of restricted access to food to reduce their weight gain to match that of the glucocorticoid injected rats, After 80 days of hormone administration the animals wer e sacrificed, The right femur was removed and tested biomechanically i n a three-point bending procedure, The left femur was used for determi nation of bone dimensions, Biomechanical parameters (ultimate load and ultimate stiffness) were then normalized to diaphyseal cross-sectiona l diameters of the femur, giving the values of ultimate bending stress and Young's modulus, Results: administration of both hormones simulta neously could not reverse the decrease in body weights, bone length, a nd diameters, or the decreased bone strength induced by glucocorticoid administration. In conclusion, growth hormone cannot prevent cortical osteopenia in female rats induced by a high dose of glucocorticoid wi th protracted effect.