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.

Growth and remodeling of the hip joint and proximal femur in adolescent dogs. A scintimetric investigation with special reference to hip dysplasia and estradiol induced changes.

The uptake of 85Sr was shown to be higher in dysplastic hip joints than in normal joints of adolescent dogs. This was interpreted as a sign of increased remodeling. In contrast, the uptake of 85Sr in the growth plate and metaphysis of the proximal femur was lower in dogs with hip dysplasia than in dogs with normal hip joints. This was interpreted as a sign of retarded growth of the proximal femur (more advanced skeletal maturation). Greyhounds of bitches, which were injected with estradiol during pregnancy, also showed retarded growth of the proximal femur. This was interpreted as a late effect of estradiol.