Effects of hypophysectomy and of LH administration on luteal phase plasma progesterone levels in the beagle bitch.

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 microgram/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.