Relationship Between the Plasma Levels of Luteinizing Hormone and Progesterone During the Normal Menstrual Cycle¹

TLDR

The study examined the timing of LH and progesterone levels throughout a normal menstrual cycle. Daily plasma samples were assayed in duplicate for progesterone using a competitive protein‑binding assay and for LH by radioimmunoassay. Progesterone remained low during the first half of the cycle, rose after the LH surge to 10–19 mµg/ml within 3–5 days, stayed elevated for 4–6 days, and fell abruptly 24 hours before menstruation without concurrent LH change.

Abstract

The temporal relationship between the concentrations of luteinizing hormone (LH) and progesterone in peripheral plasma has been determined during the course of the normal human menstrual cycle. Daily plasma samples were assayed, in duplicate, for progesterone by the competitive protein-binding method of Murphy (0.5 ml aliquots of plasma) and for LH by a radioimmunologic procedure (0.1 ml aliquots of plasma). Plasma progesterone levels remained consistently low (<0.2-1.8 mμg/ml) during the first half of the cycle and did not begin to rise until after the midcycle surge of LH became fully evident. Following the decline in plasma LH concentrations, the plasma progesterone levels increased rapidly, reaching maximal concentrations of 10–19 mμg/ml in 3–5 days. Progesterone concentrations remained elevated for 4–6 days and then fell abruptly to the initial low levels approximately 24 hr before the onset of menstruation without concomitant changes in LH concentration.