The Endocrine Basis for Slipping of the Upper Femoral Epiphysis

An endocrine basis for slipping of the upper femoral epiphysis is suggested by the fact that the lesion is nearly always accompanied by abnormalities of growth which in themselves appear to he caused by an endocrine disorder. This is especially true of those patients from whom an inadequate history of injury can be obtained. The usual disturbance of growth is the adiposo-genital syndrome, a condition characterised by obesity and deficient gonadal development ; less commonly there is a history of very rapid growth, resulting in a tall, thin child (Key 1926). In the obese children there appears to be a low level of sex-hormone in the circulation ; while in the tall, thin children there seems to be an excessively high level of growth-hormone. Both growth-hormone and sex-hormone alter the rate of proliferation of the cartilage cells in the epiphysial plates, with consequent changes in the thickness of the plates and in the rate of skeletal growth. Anterior pituitary growth-hormone stimulates the proliferation of these cells directly, with increase in the thickness of the plates and in the rate of skeletal growth (Ray et al. 1941). The sex-hormones slow the proliferation of these cells with decrease in the thickness of the plates and in the rate of skeletal growth (Gardner et al. 1943). Oestrogen produces this effect by inhibiting the secretion of growthhormone by the anterior pituitary, rather than by direct action on the epiphysial plate (Zondek 1936). It is probable that testosterone acts in the same manner, although the evidence on this point is not as clear as in the case of oestrogen (Rubinstein et al. 1939). From these observations it appears that between the time of activation of the gonads and the time that growth ceases, the structure of the epiphysial plates could be dependent on the relative levels of growth-hormone and sex-hormone in the circulation. Since it is during this interval that slipping of the upper femoral epiphysis occurs, with its associated abnormalities of growth, and since these growth disturbances are characterised by evident alterations in the level of growth-hormone and sex-hormone, it is not unreasonable to assume that an imbalance between these two endocrines is the cause of structural weakness in the epiphysial plates which makes them more susceptible to shearing stress. To test this hypothesis, an apparatus was used to measure the shearing strength of the epiphysial plates of rats. This paper reports observations made with this apparatus on animals receiving growth-hormone, animals receiving oestrogen and untreated control animals.