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Taken from WWW.pubmed.gov (testosterone studies)
Clin Chem. 2007 Apr;53(4):723-8. Epub 2007 Feb 22.
Age-Associated Discrepancy between Measured and Calculated Bioavailable Testosterone in Men.
Dechaud H, Denuziere A, Rinaldi S, Bocquet J, Lejeune H, Pugeat M.
INSERM ERM 0322, Institut des Sciences Pharmaceutiques et Biologiques, Universite de Lyon, Lyon, France, and Service de Radioanalyse,
Centre de Medecine Nucleaire, Hopital Neurologique et Cardiologique (Hospices Civils de Lyon), Bron, France.
BACKGROUND: Bioavailable (free) testosterone (BT) concentration is considered the best marker for evaluating testicular
function in men. The decrease of BT in older men is more pronounced than the decrease in total testosterone because of the
parallel increase in sex hormone-binding globulin (SHBG) concentrations. Measurement of BT is therefore crucial for the diagnosis of hypoandrogenism
in the aging male population.
METHODS: We compared BT concentrations measured by a specific RIA after ammonium sulfate precipitation (BTmeas) with those obtained by theoretical
calculations (BTcal) in plasma samples from 694 young men (14 to 49 years old) and 51 older men (50 to 81 years old). We based theoretical calculations
on Vermeulen's simplified mass equation using total testosterone and SHBG concentrations.
RESULTS: BTcal and BTmeas correlated significantly in young (Pearson r = 0.87) and aging (r = 0.89) men, but the BTcal:BTmeas ratio differed markedly
between the 2 groups (2.28 vs 3.48; P <0.001).
CONCLUSIONS: In men, there is an age-associated discrepancy between calculated and measured BT concentrations. We suggest some hypotheses for
the discrepancy, but additional studies will be performed to finally elucidate this difference in results and to determine the most appropriate method for
BT measurements in older men.
PMID: 17317886 [PubMed - as supplied by publisher]
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