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  • Title: Regulation of human gonadotropins. X. Episodic fluctuation of LH during the menstrual cycle.
    Author: Midgley AR, Jaffe RB.
    Journal: J Clin Endocrinol Metab; 1971 Dec; 33(6):962-9. PubMed ID: 5135635.
    Abstract:
    In order to determine the episodic fluctuation of LH (luteinizing hormone) during the menstrual cycle, the University of Michigan (Ann Arbor, 1971) subjected 49 samples, obtained at consecutive hourly intervals from seven women (ages 21-28) at different stages of the menstrual cycle, to radioimmunoassay. In each case, hourly analysis indicated that serum concentrations of LH, and possibly FSH (follicle stimulating hormone), are maintained as a series of peaks of varying magnitude. The length of the sampling interval prevented an exact determination of the frequency of the peaks which appeared to occur at approximately 2 1/2 hour intervals. The largest LH peaks were recorded during the ascending and descending phases of the major peak of LH at midcycle and during the early luteal phase of the cycle. The follicular phase produced the smallest LH peaks. These observations support the hypothesis that serum concentrations of LH and FSH are maintained by brief periods of release followed by periods of little or no release. Corresponding changes in LH and FSH suggest that they are released simultaneously and may be contained within the same cell. To maintain blood concentrations, the relative amount of simultaneously released LH should be greater than that of FSH since the latter has a longer half-life. Additional factors may be involved, since widely different ratios of LH/FSH can be observed at various phases of the menstrual cycle. It is suggested that accurate analysis LH and FSH concentrations requires sampling at least at half-hour intervals as is necessary for ACTH.
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