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Joint Basal and Pulsatile Hypersecretory Mechanisms Drive the Monotropic Follicle-Stimulating Hormone (FSH) Elevation in Healthy Older Men: Concurrent Preservation of the Orderliness of the FSH Release Process: A General Clinical Research Center Study¹

Division of Endocrinology, Department of Internal Medicine, National Science Foundation Center for Biological Timing, University of Virginia Health Sciences Center (J.D.V.), Charlottesville, Virginia 22908; the Endocrine Section, Medical Service, Salem Veterans Affairs Medical Center (A.I.), Salem, Virginia 24153; the Department of Pathology, Pennsylvania State University Medical School (L.M.D.), Hershey, Pennsylvania 17033-0850; and Geriatrics Medicine, Hunter Holmes McGuire Veterans Affairs Medical Center (T.M.), Richmond, Virginia 23249

Address all correspondence and requests for reprints to: Dr. J. D. Veldhuis, Division of Endocrinology, Department of Internal Medicine, Box 202, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908. E-mail: jdv{at}virginia.edu

To appraise the neuroendocrine mechanisms that underlie a selective (monotropic) elevation of serum FSH concentrations in healthy older men, we sampled blood in 11 young (ages 21–34) and 8 older men (ages 62–72) men every 2.5 min overnight. Serum FSH concentrations were quantitated in an automated, high-sensitivity, chemiluminescence-based assay. Rates of basal and pulsatile FSH secretion were estimated by deconvolution analysis, and the orderliness of the FSH release process via quantitated the approximate entropy statistic. Statistical analysis revealed that healthy older men manifest dual neuroendocrine hypersecretory mechanisims; specifically, a 2-fold increase in the basel (nonpulsatile) FSH secretion rate, and a concurrent 50% amplification of FSH secretory burst mass (and amplitude). The regularity or orderliness of ad seriatim FSH release is preserved in older individuals. We postulate that higher basel FSH secretion in older men is a consequence of reduced testosterone negative feedback, whereas amplified FSH secretory burst mass reflects net enhanced stimulation of gonadotrope cells by endogenous FSH secretagogues (e.g. GnRH and/or activin). The foregoing specific mechanisms driving heightened FSH secretion in older men contrast with the lower-amplitude pulsatility and more disorderly patterns of LH release in the same individuals. Thus, the present data illuminate an age-dependent disparity in the disruption of FSH neuroregulation in the aging male.

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