Levels of Progesterone in Peripheral Plasma During the Menstrual Cycle of the Rhesus Monkey

Abstract

Plasma progesterone concentrations throughout the menstrual cycles of 12 normal rhesus monkeys were determined using a competitive protein binding technique for progesterone analysis. Duringthe first 11 days of the cycle peripheral plasma progesterone levels were below 0.5 m[mu]g/ml, rising to a mean of 3-4 m[mu]g/ml between days 11 and 15, remaining at these values for approximately 7 days, then falling to the low levels observed during the early portion of the cycle 3 days before the onset of menstruation. Qualitative and quantitative variations in plasma progesterone concentration between individual menstrual cycles are described as are fluctuations during the luteal phases of individual cycles.