Leap of Faith: Does Serum Luteinizing Hormone Always Accurately Reflect Central Reproductive Neuroendocrine Activity?

The function of the central aspects of the hypothalamic-pituitary-gonadal axis has been assessed in a number of ways including direct measurements of the hypothalamic output and indirect measures using gonadotropin release from the pituitary as a bioassay for reproductive neuroendocrine activity. Here, methods for monitoring these various parameters are briefly reviewed and then examples presented of both concordance and discrepancy between central and peripheral measurements, with a focus on situations in which elevated gonadotropin-releasing hormone neurosecretion is not reflected accurately by pituitary luteinizing hormone release. Implications for the interpretation of gonadotropin data are discussed.