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dc.contributor.authorBremner, William J.en_US
dc.contributor.authorPlymate, Stephen R.en_US
dc.contributor.authorTenover, Joyce S.en_US
dc.contributor.authorMatsumoto, Alvin M.en_US
dc.date.accessioned2008-10-17T20:41:49Z
dc.date.available2008-10-17T20:41:49Z
dc.date.issued1987-12en_US
dc.identifier.citationJ Clin Endocrinol Metab. 1987 Dec;65(6):1118-26en_US
dc.identifier.urihttp://hdl.handle.net/1773/4378
dc.description.abstractSerum testosterone (T) levels in men decline with age while serum LH levels, as measured by RIA, increase. To assess if the decline in serum T levels in healthy aging men is paralleled by an age-related decline in the bioavailable non-sex hormone-binding globulin (SHBG)-bound fraction of T and to determine whether there are age-related changes in LH secretion or LH control of T production, we studied 29 young (aged 22-35 yr) and 26 elderly (aged 65-84 yr) healthy men. All men had single random blood samples drawn, and 14 men in each age group underwent frequent blood sampling for 24 h, both before and after 7 days of clomiphene citrate (CC) administration. Both mean 24-h serum total T levels and non-SHBG-bound T were reduced in elderly men compared to those in young men (P less than 0.05), while estradiol and SHBG levels were similar in the 2 age groups. Serum FSH determined by RIA and LH by RIA and bioassay were higher in the elderly men compared to those in young men (P less than 0.05), but the ratios of LH bioactivity to immunoreactivity and the LH pulse frequency and amplitude were similar. After CC administration, mean serum total T and non-SHBG-bound levels in young men increased by 100% and 304%, respectively, while in older men these values increased by only 32% and 8%, respectively. However, CC-stimulated LH pulse characteristics and serum levels of estradiol, SHBG, FSH, and bioactive and immunoreactive LH were similar in the 2 groups. Thus, both at baseline and after CC stimulation, elderly men had significantly lower serum total T and non-SHBG-bound (bioavailable) T levels than did young men, despite similar or increased levels of bioactive LH and similar bioactive to immunoreactive LH ratios and LH pulse characteristics. These results suggest that major age-related changes in the hypothalamic-pituitary-testicular axis occur at the level of the testes and are manifested by decreased responsiveness to bioactive LH. Administration of CC to young and elderly men resulted in similar changes in LH pulse characteristics and LH bioactivity and immunoreactivity, suggesting preserved hypothalamic-pituitary responsiveness in the elderly. AD - Geriatric Research, Education, and Clinical Center, Veterans Administration Medical Center, Seattle, Washington.en_US
dc.language.isoen_USen_US
dc.publisherEndocrine Societyen_US
dc.subjectmale contraceptionen_US
dc.subjectandrologyen_US
dc.subject5-alpha reductase inhibitorsen_US
dc.subjecttestosteroneen_US
dc.subjectgonadotropinsen_US
dc.subjectcolchicineen_US
dc.subjectklinefelter's syndromeen_US
dc.subjectreifenstein's syndromeen_US
dc.subjectspermatogenesisen_US
dc.subject.meshBiological Availabilityen_US
dc.subject.meshAgingen_US
dc.subject.meshEstradiol, blooden_US
dc.subject.meshHumansen_US
dc.subject.meshClomiphene, pharmacologyen_US
dc.subject.meshResearch Support, U.S. Gov't, Non-P.H.S.en_US
dc.subject.meshLuteinizing Hormone, blood, secretionen_US
dc.subject.meshMaleen_US
dc.subject.meshSex Hormone-Binding Globulin, analysisen_US
dc.subject.meshFollicle Stimulating Hormone, blooden_US
dc.subject.meshAgeden_US
dc.subject.meshAged, 80 and overen_US
dc.subject.meshAdulten_US
dc.subject.meshMiddle Ageden_US
dc.subject.meshTestosterone, secretionen_US
dc.subject.meshResearch Support, U.S. Gov't, P.H.S.en_US
dc.titleThe effects of aging in normal men on bioavailable testosterone and luteinizing hormone secretion: response to clomiphene citrateen_US
dc.typeArticleen_US


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