EFFECT OF GROWTH-HORMONE ON BONE - BONE-MINERAL DENSITY, TRABECULAR BONE VOLUME, AND ALKALINE-PHOSPHATASE IMPROVE OR ARE RESTORED IN THE DWARF RAT TREATED WITH GROWTH-HORMONE

Studies were performed to determine whether serum total alkaline phosp hatase (SAP), an index of bone formation; body weight; total body bone mineral density (BMD), measured by dual-energy X-ray absorptiometry; and tibial trabecular bone volume (TBV), measured by histomorphometry, are reduced in a-week-old female sexually immature Lewis dwarf (dw/dw ) rats (DW-CT, n = 9) with isolated growth hormone (GH) deficiency and , if so, whether recombinant human GH (rhGH), 200 mu g/day subcutaneou sly for 4 weeks (DW-GH, n = 7), restores them. Studies were also perfo rmed to determine if 30% dietary restriction in 2-week-old female Lewi s rats (LW-DR, n = 11) alters SAP, body weight, total BMD), or TBV com pared with pair-fed controls (LW-CT, n = 7) given an ad libitum diet. Mean SAP (91 +/- 5 versus 109 +/- 5 U/l), body weight (102 +/- 11 vers us 140 +/- 10 g), total BMD (88.5 +/- 0.3 versus 101.4 +/- 2.0 mg/cm(2 )), and TBV (19.0 +/- 1.0 versus 27.0 +/- 1.4%) were significantly low er in DW-CT than in LW-CT animals,p < 0.05. In DW-GH, rhGH significant ly increased mean SAP (130 +/- 7 U/l), bodyweight (133 +/- 10 g), tota l BMD (92.7 +/- 1.3), and TBV (24.0 +/- 1.9) compared with DW-CT anima ls. Compared with LW-CT rats, mean body weight and TBV were not differ ent, but mean SAP was significantly higher (p < 0.01) and mean total B MD was significantly lower (p < 0.003) in DW-GH rats. In LW-DR compare d with LW-CT animals, dietary restriction significantly reduced mean b ody weight (p < 0.05) but did not alter mean SAP, total BMD, or TBV. T hus, body weight, SAP, total BMD, and TBV were lower in DW-CT than in LW-CT rats. In the dose administered, SAP is markedly increased and re ductions in body weight, total BMD, and TBV are completely or partiall y restored by treatment with rhGH in young female rats caused by isola ted GH deficiency. Dietary restriction in young female rats with intac t secretion of GH prevents weight gain but does not alter SAP, total B MD, or TBV compared with animals fed ad libitum.