dc.contributor.author | Bremner, William J. | en_US |
dc.contributor.author | Plymate, Stephen R. | en_US |
dc.contributor.author | Tenover, Joyce S. | en_US |
dc.contributor.author | Matsumoto, Alvin M. | en_US |
dc.date.accessioned | 2008-10-17T20:41:49Z | |
dc.date.available | 2008-10-17T20:41:49Z | |
dc.date.issued | 1987-12 | en_US |
dc.identifier.citation | J Clin Endocrinol Metab. 1987 Dec;65(6):1118-26 | en_US |
dc.identifier.uri | http://hdl.handle.net/1773/4378 | |
dc.description.abstract | Serum 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.iso | en_US | en_US |
dc.publisher | Endocrine Society | en_US |
dc.subject | male contraception | en_US |
dc.subject | andrology | en_US |
dc.subject | 5-alpha reductase inhibitors | en_US |
dc.subject | testosterone | en_US |
dc.subject | gonadotropins | en_US |
dc.subject | colchicine | en_US |
dc.subject | klinefelter's syndrome | en_US |
dc.subject | reifenstein's syndrome | en_US |
dc.subject | spermatogenesis | en_US |
dc.subject.mesh | Biological Availability | en_US |
dc.subject.mesh | Aging | en_US |
dc.subject.mesh | Estradiol, blood | en_US |
dc.subject.mesh | Humans | en_US |
dc.subject.mesh | Clomiphene, pharmacology | en_US |
dc.subject.mesh | Research Support, U.S. Gov't, Non-P.H.S. | en_US |
dc.subject.mesh | Luteinizing Hormone, blood, secretion | en_US |
dc.subject.mesh | Male | en_US |
dc.subject.mesh | Sex Hormone-Binding Globulin, analysis | en_US |
dc.subject.mesh | Follicle Stimulating Hormone, blood | en_US |
dc.subject.mesh | Aged | en_US |
dc.subject.mesh | Aged, 80 and over | en_US |
dc.subject.mesh | Adult | en_US |
dc.subject.mesh | Middle Aged | en_US |
dc.subject.mesh | Testosterone, secretion | en_US |
dc.subject.mesh | Research Support, U.S. Gov't, P.H.S. | en_US |
dc.title | The effects of aging in normal men on bioavailable testosterone and luteinizing hormone secretion: response to clomiphene citrate | en_US |
dc.type | Article | en_US |