1. The long-term administration of pituitary growth hormone to fifteen normal female rats after their weight had reached a plateau resulted in atypical hyperplasia of small follicles in five rats and in solid tumors of the ovaries in two rats. No similar changes were present in the control rats.

  2. The atypical hyperplasia of small follicles is considered an early stage in the development of granulosa-cell and interstitial-cell tumors of the ovary.

  3. Fibro-adenomata of the mammary tissue occurred more frequently, were larger, and were often multiple in rats injected with growth hormone.

  4. The above changes are regarded as the result of the chronic administration of pituitary growth hormone which causes a marked disturbance in the normal function of the pituitary gland.

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Aided by grants from the Public Health Service RG-409 and C421; the Research Board of the University of California; the American Cancer Society, Inc., N.Y.; and the University of California Cancer Grant.

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©1950 American Association for Cancer Research.
1950
Cancer Research, Inc.