Differences in the apparent metabolic clearance rate of testosterone in young and older men with gonadotropin suppression receiving graded doses of testosterone.
J Clin Endocrinol Metab
; 91(11): 4669-75, 2006 Nov.
Article
en En
| MEDLINE
| ID: mdl-16912120
ABSTRACT
BACKGROUND:
Recently we found that testosterone levels are higher in older men than young men receiving exogenous testosterone. We hypothesized that older men have lower apparent testosterone metabolic clearance rates (aMCR-T) that contribute to higher testosterone levels.OBJECTIVE:
The objective of the study was to compare aMCR-T in older and young men and identify predictors of aMCR-T.METHODS:
Sixty-one younger (19-35 yr) and 60 older (59-75 yr) men were given a monthly GnRH agonist and weekly testosterone enanthate (TE) (25, 50, 125, 300, or 600 mg) for 5 months. Estimated aMCR-T was calculated from the amount of TE delivered weekly and trough serum testosterone concentrations, corrected for real-time absorption kinetics from the im testosterone depot.RESULTS:
Older men had lower total (316 +/- 13 vs. 585 +/- 26 ng/dl, P < 0.00001) and free testosterone (4 +/- 0.1 vs. 6 +/- 0.3 ng/dl, P < 0.00001) and higher SHBG (52 +/- 3 vs. 33 +/- 2 nmol/liter, P < 0.00001) than younger men at baseline. Total and free testosterones increased with TE dose and were higher in older men than young men in the 125-, 300-, and 600-mg dose groups. aMCR-T was lower in older men than young men (1390 +/- 69 vs. 1821 +/- 102 liter/d, P = 0.006). aMCR-T correlated negatively with age (P = 0.0007), SHBG (P = 0.046), and total testosterone during treatment (P = 0.02) and percent body fat at baseline (P = 0.01) and during treatment (P = 0.004). aMCR-T correlated positively with lean body mass at baseline (P = 0.03) and during treatment (P = 0.01). In multiple regression models, significant predictors of aMCR-T included lean body mass (P = 0.008), percent fat mass (P = 0.009), and SHBG (P = 0.001).CONCLUSIONS:
Higher testosterone levels in older men receiving TE were associated with an age-related decrease in apparent testosterone metabolic clearance rates. Body composition and SHBG were significant predictors of aMCR-T.
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Banco de datos:
MEDLINE
Asunto principal:
Testosterona
/
Gonadotropinas
/
Hipogonadismo
Tipo de estudio:
Clinical_trials
/
Prognostic_studies
Límite:
Adult
/
Aged
/
Humans
/
Male
/
Middle aged
Idioma:
En
Año:
2006
Tipo del documento:
Article