THE REGULATION OF CORPUS LUTEUM FUNCTION BY HYPOPHYSIAL LUTEOTROPHIN1

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Abstract
A method was developed for assay of a substance, hypophysial luteotrophin, which maintained the function of formed corpora lutea. Immature ? rats were treated 4 days with gonadotrophin to induce corpus luteum formation and then treated with estradiol di-propionate to sustain a continued estrogen action. The modifying influence of the active corpora lutea on the estrogen action was used as an index of luteal function. Hypophysectomy in such animals was followed by all signs of unopposed estrogen action unless luteotrophin was given. The persistence of vaginal mucification indicated that the corpora lutea continued to function in the absence of the hypophysis under the influence of the injected hormone. Luteotrophin was extracted from pituitaries of sheep and was separated from follicle-stimulating and luteinizing hormones and from thyrotrophin. It was distinct from the growth and adrenotrophic factors and was not responsible for proliferation of mammary lobules in hy-pophysectomized rats. The role of this hormone in the regulation of corpus luteum function and the control of the reproductive cycle were discussed.