TY - JOUR
T1 - Aging in healthy men impairs recombinant human luteinizing hormone (LH)-stimulated testosterone secretion monitored under a two-day intravenous
AU - Liu, Peter Y.
AU - Takahashi, Paul Y.
AU - Roebuck, Pamela D.
AU - Iranmanesh, Ali
AU - Veldhuis, Johannes D.
PY - 2005/10
Y1 - 2005/10
N2 - Context: Testosterone (Te) depletion in aging men in principle could reflect deficits in the hypothalamus, pituitary gland, or testis. Available pharmacological studies of possible failure of Leydig cell steroidogenesis remain inconclusive. Objective: The objective of the study was to assess Te secretion in older and young men in response to near physiological LH stimulation. Intervention: Pulsatile iv infusion of recombinant human LH was administered for 2 d to stimulate Te secretion during suppression of endogenous LH concentrations with a potent selective GnRH receptor antagonist (ganirelix). Subjects/Context: Healthy older (aged 60-73 yr, n = 8) and young (19-30 yr, n = 13) men were studied in an academic setting. Measures: Pulsatile LH and Te concentrations on the second day of exogenous LH stimulation were measured. Results: Serum ganirelix concentrations and infused LH pulse increments were similar by age. In contrast, older subjects manifested: 1) reduced mean Te concentrations (P = 0.016), Te peak heights (P = 0.014), increments (P = 0.010), summed areas (P < 0.013), and interpeak Te concentrations (P = 0.023); 2) decreased Te to LH concentration ratios (P = 0.002); 3) diminished LH-Te feed-forward synchrony (P = 0.020); and 4) a blunted amplitude (P = 0.036) and advanced phase (P = 0.013) of diurnal Te rhythms. Conclusion: A novel regimen of pulsatile LH stimulation for 48 h during GnRH receptor blockade unmasks deficits in pulsatile, basal, synchronous, and nyctohemeral Te secretion in healthy older men. These findings do not exclude concomitant defects in GnRH outflow and/or Te-negative feedback in the aging male.
AB - Context: Testosterone (Te) depletion in aging men in principle could reflect deficits in the hypothalamus, pituitary gland, or testis. Available pharmacological studies of possible failure of Leydig cell steroidogenesis remain inconclusive. Objective: The objective of the study was to assess Te secretion in older and young men in response to near physiological LH stimulation. Intervention: Pulsatile iv infusion of recombinant human LH was administered for 2 d to stimulate Te secretion during suppression of endogenous LH concentrations with a potent selective GnRH receptor antagonist (ganirelix). Subjects/Context: Healthy older (aged 60-73 yr, n = 8) and young (19-30 yr, n = 13) men were studied in an academic setting. Measures: Pulsatile LH and Te concentrations on the second day of exogenous LH stimulation were measured. Results: Serum ganirelix concentrations and infused LH pulse increments were similar by age. In contrast, older subjects manifested: 1) reduced mean Te concentrations (P = 0.016), Te peak heights (P = 0.014), increments (P = 0.010), summed areas (P < 0.013), and interpeak Te concentrations (P = 0.023); 2) decreased Te to LH concentration ratios (P = 0.002); 3) diminished LH-Te feed-forward synchrony (P = 0.020); and 4) a blunted amplitude (P = 0.036) and advanced phase (P = 0.013) of diurnal Te rhythms. Conclusion: A novel regimen of pulsatile LH stimulation for 48 h during GnRH receptor blockade unmasks deficits in pulsatile, basal, synchronous, and nyctohemeral Te secretion in healthy older men. These findings do not exclude concomitant defects in GnRH outflow and/or Te-negative feedback in the aging male.
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U2 - 10.1210/jc.2005-0909
DO - 10.1210/jc.2005-0909
M3 - Article
C2 - 16030163
AN - SCOPUS:26244451952
SN - 0021-972X
VL - 90
SP - 5544
EP - 5550
JO - Journal of Clinical Endocrinology and Metabolism
JF - Journal of Clinical Endocrinology and Metabolism
IS - 10
ER -