CONTINUOUS AND DISCONTINUOUS TREATMENT WITH ESTROGENS IN EXPERIMENTAL TUMORIGENESIS1

Abstract

The toxic effects of a prolonged treatment with mono-benzoated estradiol have been studied in the [female] guinea pig under different timing conditions. A given quantity of esterified estradiol which when injected thrice weekly (47 injections in the course of 113 days) produced tumorigenic and other toxic effects (uterine bleeding, monstrous development of the uterus, uterine and extrauterine fibroids, polyps of the endometrium extending into the vagina), lost its toxic faculties if each wk. of injs. was followed by 2-3 wks. free of injs. (47 injs. in the course of 365 days). With similar intervals free of injs. quantities of esterified estradiol many times greater than the tumorigenic one were still unable to produce the above mentioned toxic effects. The importance of these exptl. findings for the treatment with estrogens in [female][female] is discussed.