Luteotrophic Properties of Some Pituitary Hormones in Nonpregnant or Pregnant Hypophysectomized Ewes

Abstract

Hypophysectomy of cyclic or pregnant sheep causes immediate and complete degeneration of the corpus luteum (CL), thus indicating that sheep CL need a hypophysial luteotrophic substance for formation and maintenance. Previous attempts to maintain CL in hypophysectomized ewes with intact uteri have failed when various hormones were injected. The present study presents data which show that crude pituitary gland extracts containing both FSH and LH, as well as other hypophysial hormones, are luteotrophic in hypophysectomized nonpregnant or pregnant sheep. Crude LH alone is also luteotrophic, while purified LH is only partially luteotrophic in that it does not allow complete degeneration of CL, and can maintain pregnancy for only a limited time. In contrast, FSH, prolactin, or estrogen alone show no luteotrophic properties in hypophysectomized animals. The reason crude LH maintained CL in these experiments lies in the fact that it was infused constantly. It is estimated that much less than 1 μg of LH/hr actually reached the CL. (Endocrinology82:. 818, 1968)