Mechanistic bases for age-related androgen deficiency
Principal Investigator: Johannes Veldhuis
Affiliation: Mayo Clinic
Abstract: Aging in men results in progressive impoverishment of systemic androgen availability. Epidemiological data establish a close association between hypoandrogenemia and sarcopenia, osteopenia, visceral adiposity, insulin resistance, dyslipidemia, reduced quality of life and institutionalization. However, the precise mechanistic bases of reduced testosterone production in the older male are not known. The present proposal is predicated on the thesis that the male gonadal axis is regulated via reciprocal interactions among all three of GnRH, LH and testosterone. Interpreted from this vantage and compelling preliminary data, we postulate that the primary mechanisms of aging-related testosterone depletion include the following: HYPOTHESIS I: Restricted hypothalamic GnRH drive, which reduces the mass of LH contained in pulses. HYPOTHESIS II: Impaired Leydig-cell steroidogenesis, which enforces systemic hypoandrogenemia. HYPOTHESIS III: Reduced negative feedback by testosterone, which unleashes high-frequency, low- amplitude and irregular LH release. The immediate objective is to elucidate the relative timing, importance and prevalence of the foregoing putative regulatory deficits in the same 40 individuals as a function of age within the continuum 18-80 yr. These data will drive formulation of an R01 to investigate age-related adaptations in the gonadal axis longitudinally. The long-term goal is to stimulate novel insights into mechanistically selective preventive strategies to preserve anabolic support and enhance quality of life, physical and cognitive function and capable independent activities of older citizens. PUBLIC PRECIS. Studies focus on what causes low sex-hormone levels in older men. Low testosterone is important, because it predicts relative physical frailty (thin bones, reduced muscle strength and stamina), less life satisfaction, greater abdominal fat gain and increased cardiovascular risk. Knowing why testosterone falls should help foster new and safer ways to prevent the problem.
Funding Period: 2006-03-01 - 2009-02-28
more information: NIH RePORT
- An ensemble model of the male gonadal axis: illustrative application in aging menDaniel M Keenan
Department of Statistics, University of Virginia, Charlottesville, Virginia 22903, USA
Endocrinology 147:2817-28. 2006..The generality of the present integrative model suggests utility in parsing interlinked adaptations in other physiological networks...
- Age attenuates testosterone secretion driven by amplitude-varying pulses of recombinant human luteinizing hormone during acute gonadotrope inhibition in healthy menPaul Y Takahashi
Endocrine Research Unit, Department of Internal Medicine, General Clinical Research Center, Mayo Medical and Graduate Schools of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA
J Clin Endocrinol Metab 92:3626-32. 2007..Whether testosterone (Te) depletion in aging men reflects deficits in the testis, hypothalamus, and/or pituitary gland is unknown...
- A noninvasive measure of negative-feedback strength, approximate entropy, unmasks strong diurnal variations in the regularity of LH secretionPeter Y Liu
Endocrine Research Unit, Mayo School of Graduate Medical Education, General Clinical Research Center, Mayo Clinic, Rochester, MN 55905, USA
Am J Physiol Endocrinol Metab 293:E1409-15. 2007..These outcomes suggest that ApEn may have general utility in probing dynamic mechanisms mediating feedback in other endocrine systems...
- Increased basal and pulsatile secretion of FSH and LH in young men with 47,XXY or 46,XX karyotypesLise Aksglaede
University Department of Growth and Reproduction GR, Rigshospitalet, University of Copenhagen, Section 5064, Blegdamsvej 9, DK 2100 Copenhagen Ø, Denmark
Eur J Endocrinol 158:803-10. 2008..The aim of this study was to investigate the neuroendocrine integrity of the pituitary-gonadal axis in patients with primary testicular failure due to supernumerary X chromosomes...
- Motivations and methods for analyzing pulsatile hormone secretionJohannes D Veldhuis
Endocrine Research Unit, Department of Internal Medicine, Mayo Medical School, Mayo School of Graduate Medical Education, Center for Translational Science Activities, Mayo Clinic, Rochester, Minnesota 55905, USA
Endocr Rev 29:823-64. 2008..This review will focus on the motivations driving and the methodologies used for such analyses...
- Sensitivity and specificity of pulse detection using a new deconvolution methodPeter Y Liu
Endocrine Research Unit, Department of Internal Medicine, Mayo Medical School, Mayo School of Graduate MedicalEducation, Center for Translational Science Activities, Mayo Clinic, Rochester, Minnesota 55905, USA
Am J Physiol Endocrinol Metab 297:E538-44. 2009..We conclude that an objective automated pulse detection deconvolution procedure has high sensitivity and specificity, thus offering a platform for quantitative neuroendocrine analyses...
- Testosterone's short-term positive effect on luteinizing-hormone secretory-burst mass and its negative effect on secretory-burst frequency are attenuated in middle-aged menPeter Y Liu
Endocrine Research Unit, Mayo Medical School, Mayo School of Graduate Medical Education, Center for Translational Science Activities, Mayo Clinic, Rochester, Minnesota 55905, USA
J Clin Endocrinol Metab 94:3978-86. 2009..Testosterone (T) production declines and LH pulses become smaller and more frequent in middle-aged men. The mechanisms underlying these changes are not known...