Plasma substance-P and substance-K and gonadal steroids in relation to the gonadotropin surge in normal human reproductive cycles

Purpose: This study was designed to examine changes in peripheral plasma substance-P and -K levels, their association with follicle-stimulating hormone and luteinizing hormone release in normal reproductive cycles in humans, and their correlation with plasma estradiol and progesterone. Methods: Fourteen healthy, normally, menstruating women underwent daily blood sampling (cycle day 4, 4-14 days) for measurement of estradiol, progesterone, luteinizing hormone, and follicle-stimulating hormone, substances-P and -K, and daily transvaginal ultrasounds assessing follicular growth and documentation of ovulation. Results: Estradiol peaked on day 13, luteinizing hormone and follicle-stimulating hormone peaked on day 14, and progesterone began an exponential increase on about day 13. Conclusions: In contrast to other experimental designs using in vitro or in vivo rat or monkey tissue, peripheral levels of substances-P (P = 0.8391) and -K (P = 0.3205) reflected no modulation related to midcycle gonadotropin release in cycling woman.