Luteal-phase progesterone levels in 5 beagle bitches fell to 0·3–0·4 ng/ml within 3–17 days after hypophysectomies on Day 10–50 of the cycle. Plasma progesterone in 6 bitches increased (P < 0·01) within 3 h after LH (100 µg/kg) injection between Days 35 and 55 of the cycle. Normal luteal function in the bitch appears to require continuous pituitary trophic support perhaps involving LH.
