New paper from Oct 2019
Calculated ref range from the data presented in the study linked below is:
NHANES III 304 - 944 ng/dl
cont NHANES 348 - 1005 ng/dl
We used cross-sectional data for never-smoking, lean men ≥20 years without diabetes, myocardial infarction, congestive heart failure, stroke, or cancer, without use of hormone-influencing medications, and participated in morning sessions of National Health and Nutrition Examination Survey (NHANES) III (phase I 1988–1991) or continuous NHANES (1999–2004).
In NHANES III, in never-smoking, lean men without comorbidities, median (25th, 75th percentile) testosterone was 4% to 9% higher than all men—20 to 39 years: 6.24 (5.16, 7.51), 40 to 59: 5.37 (3.83, 6.49). In continuous NHANES, in never-smoking, lean men without comorbidities, levels were 13% to 24% higher than all men—20 to 39 years: 6.26 (5.32, 7.27), 40 to 59: 5.86 (4.91, 6.55), and ≥60: 4.22 (3.74, 5.73). In never-smoking, lean men without comorbidities, median estimated free testosterone was similar to (NHANES III) or slightly higher than (continuous NHANES) in all men.
Third, for quantitating testosterone concentration, we used the Elecsys Testosterone Immunoassay (Roche Diagnostics), which was FDA approved and in wide clinical use. The method was standardized by isotope dilution gas chromatography mass spectrometry .