The mechanical strength of the growth plate under the influence of sex hormones.

As sex hormones are considered to play a role in the etiology of the slipped upper femoral epiphysis, the influence of sex hormones on the mechanical strength of the epiphyseal plate was investigated in 310 female and 70 male rats. Ovariectomy weakened the strength of the growth plate while orchiectomy strengthened it. Estrogen given after ovariectomy, markedly strengthened the plate. Histologic examination revealed that the width of the growth plate was narrower in the mechanically stronger group. Hydroxyproline content increased and hexosamine content decreased in the epiphyseal plates of the mechanically stronger group. These observations confirm the view that sex hormones, especially estrogen, regulate the mechanical, morphologic, and biochemical functions of the growth plate.