Hypophysectomy and Tumor Growth: A Supplementary Statement

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Abstract
The retarding effect of pituitary removal on the rate of growth of Walker mammary carcinoma No. 256 which we originally observed (1, 6) has been confirmed by other workers. McEuen and Thomson (3) and Reiss and coworkers (5) have observed similar results using the same tumor as well as extending the observation to others. Approaching the problem from another angle, Sugiura and Benedict (7) have shown that of many endocrine extracts used, only those from the anterior lobe of the pituitary possessed tumor-growth-stimulating properties. This was observed for mouse melanoma and Sugiura rat sarcoma but was not manifest in a number of other tumors used. In a recent article Bischoff, Maxwell and Ullmann (2) refer to our earlier observations and deduce, following certain assumptions, that the effect of hypophysectomy on the rate of growth of Walker carcinoma No. 256 is no greater than that produced by irradiating the pituitary area with large doses of x-rays. By recalculating our data using the formula which they applied to their series1 a significant difference becomes apparent, as may be observed from Table I. Thus in the three series of experiments by Bischoff et al, which are comparable with hypophysectomy using the Walker tumor, the greatest difference observed was 3.47 times the standard deviation at the end of three weeks, whereas the difference between our control and hypophysectomized groups at three weeks is 4.39 times the standard deviation and this increases to 6.02 times at the end of the fourth week, when the irradiated animals of Bischoff et al cease to show a significant difference. Attention is called to groups D and E of our original paper (1), both of which are control groups. The 8 animals comprising group D had operative exposure of the pituitary but no removal of gland substance. In the 16 animals of group E there was no operative procedure. The tumors of group D were consistently larger than those of group E, a difference which can be observed in the present table. The differences border on statistical significance at the end of two and three weeks but not at four weeks, assuming three times the standard deviation as significant. The stimulation observed is approximately of the same degree statistically as the depression observed by Bischoff et al in their irradiated animals, using the same tumor.

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