Recent researchย from over 9,000 men published in the Journal of Clinical Endocrinology & Metabolismย offers insight into what they classify ‘normal testosterone’ levels. Here were the study parameters:
Objective:To establish harmonized reference ranges for total testosterone in men that can be applied across laboratories by cross-calibrating cohort-specific assays to a reference method and standard.
Population:9054 community-dwelling men in cohort studies in the United States and Europe: Framingham Heart Study; European Male Aging Study; Osteoporotic Fractures in Men Study; Male Sibling Study of Osteoporosis.
Methods:Testosterone concentrations in 100 participants in each of the four cohorts were measured using a reference method at Centers for Disease Control. Generalized additive models and Bland-Altman analyses supported the use of normalizing equations for transformation between cohort-specific and CDC values. Normalizing equations, generated using Passing-Bablok regression, were employed to generate harmonized values, which were used to derive standardized, age-specific reference ranges.
Here is their conclusion:
The harmonized normal range (2.5th-to-97.5th percentile) in non obese, population of European and American men, 19-39 years, is 264-916 ng/dL. A substantial proportion of inter-cohort variation in testosterone levels is due to assay differences. These data demonstrate the feasibility of generating harmonized reference ranges for testosterone that can be applied to assays, which have been calibrated to a reference method and calibrator.
So in a nutshell for those of you not interested in reading mundane medical research, they believe that ‘normal T’ is a range value of 264 to 916 ngย per deciliter for men between 19-39 years of age. For any man educated to the signs, symptoms and lab readingsย of sub-optimal testosterone levels-this study should makeย you cringe. Quite honestly- claiming that 264 Testosterone is a ‘normal and acceptable level’ of Testosterone for any younger man (especially in the younger age ranges used in the study) is just utter bullshit. It makes me angry the mainstream continues to put forth articles like this confusing men further from the reality of what truly defines testosterone deficiency.