Estradiol induced skeletal changes. The long term effect of prenatal and postnatal administration in beagles.

Beagle pups were injected with 200 mug estradiol benzoate per kg body weight daily 5 times weekly during the first 8 weeks of life. The skeletal development of the pups was followed from 8 weeks to 18 months of age. The femoral heads were smaller and the hip joints more unstable in these pups than in controls from 10 weeks of age. The femoral head ossification center increased more rapidly in size in these pups. The bone mass was also increased. Pups of pregnant bitches, which were injected with estradiol benzoate during the last three weeks of gestation, were studied. The highest total dose injected to the bitches was 90 mug per kg bodyweight. Changes in the hip joints such as small femoral heads and increased instability were found in these pups at 8 and 10 weeks of age. Bone mass was less in these pups than in controls. In adult life these pups had loose hips but they did not develop the complete picture of hip dysplasia. The present investigation demonstrates that the early changes in the hip joints caused by estradiol lead to hip dysplasia.