Action of testosterone propionate on the output of pituitary gonadotrophins in mice.

Ovarian tumors can be induced by a disturb ance of the hormonal balance in animals of several species. Ovaries transplanted in castrated animals to a region drained by the portal system (e.g., spleen, pancreas) become tumorous. The liver partly in activates the estrogens formed by the transplanted ovary. The low level of circulating estrogens re suits in a higher output of pituitary gonadotro phins, which is presumably responsible for the ini tiation of the tumors in the ovaries (4, 5, 11, 16— 2.0, 2.2.,2.4, 2.6, and 2.7). Exogenous gonadotrophins may accelerate the development of these tumors (3), hypophyseal transplants tend to have the same effect (2.8), as does union in parabiosis with two castrates (2.5). Tumors do not form if the ovarian graft adheres to the parietes. The estrogens formed by the graft find their way into the general circulation, and their level remains high enough to control the secretion of pituitary gonadotrophins. Tumor for mation also does not occur if one normal gonad is present, or if the animal is given estrogens or an drogens. Mice exposed to adequate doses of x-rays ac quire similar tumors (1, 7, 10, 12., 14, 1@,2.1, and 30). In this case two factors could be involved: a primary local action and a secondary effect due to the hormonal imbalance caused by the irradiation. The primary local action can be excluded, since unilaterally irradiated ovaries do not become tu morons. The disturbed hormonal balance seems to be important here also, since the existence of one normal ovary or the injection of estrogens prevents tumor formation (13, 14). As mentioned above, androgens (testosterone