Rational approach to categorizing testosterone levels using community-based reference ranges

Image: Testosterone Levels

Reference ranges for testosterone in men generated using liquid chromatography tandem mass spectrometry in a community-based sample of healthy nonobese young men in the Framingham Heart Study and applied to three geographically distinct cohorts. Bhasin S, Pencina M, Jasuja GK, et al. J Clin Endocrinol Metab 2011;96(8):2430-2439.

This study1 generated reference limits for total and free testosterone levels in a community-based sample of nonobese healthy young (19-40 years) men enrolled in the Framingham Heart Study third generation cohort.2 These reference limits were then applied to three geographically distinct cohorts of community dwelling men drawn from the Framingham Heart Study (FHS) generations 2 and 3,2 the European Male Aging Study (EMAS)3,4 and the Osteoporotic Fractures in Men Study (MrOS).5 A ‘gold standard’ assay method, liquid chromatography tandem mass spectrometry (LC-MS/MS)6 was used throughout to determine total testosterone levels; free testosterone levels were calculated using a published law-of-mass-action equation.7
Researchers then investigated whether men deemed to have low total and free testosterone levels by the proposed reference limits had a higher prevalence of physical dysfunction, sexual symptoms, and diabetes mellitus, the three categories of conditions most consistently associated with low testosterone levels. Physical function measures (including low walking speed, difficulty climbing stairs, self-reported mobility limitation and frailty) and diabetes were investigated in all three cohorts; sexual symptoms (including decreased morning erections, erectile dysfunction and decreased frequency of sexual thoughts) were available only in EMAS.

Key Points

Reference ranges of total and free testosterone (TT and FT)

  • In the reference sample of 456 men, the mean (SD)and median (quartile) values were:1


    • TT: 723.8 (221.1) and 698.7 (296.5) ng/dL
    • FT: 141. 8 (45.0) and 134.0 (60.0) pg/mL
  • Values below the 2.5th percentile of reference sample were classified as low:1


    • TT: 348.3 ng/dL (12.1 nmol/L)
    • FT: 70.0 pg/mL (243 pmol/L)
Association of low T with sexual, physical and metabolic conditions

  • The association of low TT and FT was determined in terms of:1


    • Physical dysfunction and sexual symptoms (EMAS only)
    • Diabetes mellitus (in FHS generations 2 and 3, EMAS, and the Osteoporotic Fractures in Men Study)
  • Men with low TT and FT were more likely to have a higher incidence of physical dysfunction, such as slow walking speed, difficulty climbing stairs or frailty, and diabetes than those with normal levels (all 3 samples)1
  • Men with low TT and FT were more likely to report sexual symptoms, such as decreased morning erections, erectile dysfunction and decreased frequency of sexual thoughts, than men with normal levels (EMAS) and were more likely to have at least one of the following:1


    • Sexual symptoms (EMAS)
    • Physical dysfunction, or
    • Diabetes
Conclusions

  • These reference ranges generated in a community-based sample of men provide a rational basis for categorizing testosterone levels as low or normal1
  • Men with low TT or FT had a higher prevalence of physical dysfunction, sexual dysfunction, and diabetes.1

What is known

The accurate diagnosis of androgen deficiency is based on the determination of whether circulating testosterone levels are low or normal.8-10 However, approaches to generate rigorous testosterone reference ranges have been limited by the inherent selection bias when hospital- or clinic-based patient samples have been used, and by the accuracy of the assay methods. Thus, the categorization of total and free testosterone levels into normal or low values has been associated with a substantial risk of misclassification.

What this study adds

This study has several strengths. It used a ‘gold standard’ assay method with high specificity, sensitivity and accuracy to measure total testosterone levels in a general population. The FHS reference cohort is a large community-based sample of healthy men, both young and older, approaching the definition of an optimum sample as described by the International Federation of Clinical Chemistry.11-13 The researchers then showed that, consistently across the three geographically distinct samples, men with low total and free testosterone levels, according to these thresholds, had a higher prevalence of the three categories of conditions consistently associated with low testosterone levels: physical dysfunction, sexual symptoms, and diabetes.
Prospective randomized trials and incident outcome studies will be necessary to determine how well the discriminating thresholds identified in this study can be applied to the clinical diagnosis of testosterone deficiency.

References

1. Bhasin S, Pencina M, Jasuja GK, et al. Reference ranges for testosterone in men generated using liquid chromatography tandem mass spectrometry in a community-based sample of healthy nonobese young men in the Framingham Heart Study and applied to three geographically distinct cohorts. J Clin Endocrinol Metab 2011;96(8):2430-2439.
2. Splansky GL, Corey D, Yang Q, et al. The Third Generation Cohort of the National Heart, Lung, and Blood Institute's Framingham Heart Study: design, recruitment, and initial examination. Am J Epidemiol 2007;165(11):1328-1335.
3. Lee DM, O'Neill TW, Pye SR, et al. The European Male Ageing Study (EMAS): design, methods and recruitment. Int J Androl 2009;32(1):11-24.
4. Wu FC, Tajar A, Beynon JM, et al. Identification of late-onset hypogonadism in middle-aged and elderly men. N Engl J Med 2010;363(2):123-135.
5. Orwoll E, Blank JB, Barrett-Connor E, et al. Design and baseline characteristics of the osteoporotic fractures in men (MrOS) study--a large observational study of the determinants of fracture in older men. Contemp Clin Trials 2005;26(5):569-585.
6. Wang C, Catlin DH, Demers LM, et al. Measurement of total serum testosterone in adult men: comparison of current laboratory methods versus liquid chromatography-tandem mass spectrometry. J Clin Endocrinol Metab 2004;89(2):534-543.
7. Mazer NA. A novel spreadsheet method for calculating the free serum concentrations of testosterone, dihydrotestosterone, estradiol, estrone and cortisol: with illustrative examples from male and female populations. Steroids 2009;74(6):512-519.
8. Bhasin S, Cunningham GR, Hayes FJ, et al. Testosterone therapy in men with androgen deficiency syndromes: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2010;95(6):2536-2559.
9. Rosner W, Auchus RJ, Azziz R, et al. Position statement: Utility, limitations, and pitfalls in measuring testosterone: an Endocrine Society position statement. J Clin Endocrinol Metab 2007;92(2):405-413.
10. Bhasin S, Zhang A, Coviello A, et al. The impact of assay quality and reference ranges on clinical decision making in the diagnosis of androgen disorders. Steroids 2008;73(13):1311-1317.
11. Petitclerc C, Solberg HE. Approved recommendation (1987) on the theory of reference values. Part 2. Selection of individuals for the production of reference values. J Clin Chem Clin Biochem 1987;25:639-644.
12. Elveback L. The population of healthy persons as a source of reference information. Hum Pathol 1973;4(1):9-16.
13. Lott JA, Mitchell LC, Moeschberger ML, et al. Estimation of reference ranges: how many subjects are needed? Clin Chem 1992;38(5):648-650.

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Last updated: 2018
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