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Endocrinology and Metabolism |
1 Department of Endocrinology, Vrije Universiteit Medical Center, Amsterdam, The Netherlands.
2 Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, The Netherlands.
3 Departments of Internal Medicine; and 4
Epidemiology and Biostatistics, Erasmus Medical Center, Rotterdam, The Netherlands.
aAddress correspondence to this author at: Department of Endocrinology, VU University Medical Center, de Boelelaan 1117, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands. E-mail p.deronde{at}vumc.nl.
Background: Estimation of serum concentrations of free testosterone (FT) and bioavailable testosterone (bioT) by calculation is an inexpensive and uncomplicated method. We compared results obtained with 5 different algorithms.
Methods: We used 5 different published algorithms [described by Sodergard et al. (bioTS and FTS), Vermeulen et al. (bioTV and FTV), Emadi-Konjin et al. (bioTE), Morris et al. (bioTM), and Ly et al. (FTL)] to estimate bioT and FT concentrations in samples obtained from 399 independently living men (ages 40–80 years) participating in a cross-sectional, single-center study.
Results: Mean bioT was highest for bioTS (10.4 nmol/L) and lowest for bioTE (3.87 nmol/L). Mean FT was highest for FTS (0.41 nmol/L), followed by FTV (0.35 nmol/L), and FTL (0.29 nmol/L). For bioT concentrations, the Pearson correlation coefficient was highest for the association between bioTS and bioTV (r = 0.98) and lowest between bioTM and bioTE (r = 0.66). FTL was significantly associated with both FTS (r = 0.96) and FTV (r = 0.88). The Pearson correlation coefficient for the association between FTL and bioTM almost reached 1.0. Bland-Altman analysis showed large differences between the results of different algorithms. BioTM, bioTE, bioTV, and FTL were all significantly associated with sex hormone binding globulin (SHBG) concentrations.
Conclusion: Algorithms to calculate FT and bioT must be revalidated in the local setting, otherwise over- or underestimation of FT and bioT concentrations can occur. Additionally, confounding of the results by SHBG concentrations may be introduced.
The following articles in journals at HighWire Press have cited this article:
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  G. Sartorius, L. P Ly, K. Sikaris, R. McLachlan, and D. J Handelsman Predictive accuracy and sources of variability in calculated free testosterone estimates Ann Clin Biochem, March 1, 2009; 46(2): 137 - 143. [Abstract] [Full Text] [PDF]
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 J. A. Talbot, R. Sheldrick, H. Caswell, and S. Duncan Sexual function in men with epilepsy: How important is testosterone? Neurology, April 15, 2008; 70(16): 1346 - 1352. [Abstract] [Full Text] [PDF]
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 M. E. Kevenaar, J. S. E. Laven, S. L. Fong, A. G. Uitterlinden, F. H. de Jong, A. P. N. Themmen, and J. A. Visser A Functional Anti-Mullerian Hormone Gene Polymorphism Is Associated with Follicle Number and Androgen Levels in Polycystic Ovary Syndrome Patients J. Clin. Endocrinol. Metab., April 1, 2008; 93(4): 1310 - 1316. [Abstract] [Full Text] [PDF]
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 H. Dechaud, A. Denuziere, S. Rinaldi, J. Bocquet, H. Lejeune, and M. Pugeat Age-Associated Discrepancy between Measured and Calculated Bioavailable Testosterone in Men Clin. Chem., April 1, 2007; 53(4): 723 - 728. [Abstract] [Full Text] [PDF]
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