Measurement of testosterone: how important is a morning blood draw?

Abstract

Objective:

Since testosterone levels exhibit a circadian variation with peak levels in the morning, evidence-based guidelines recommend measuring morning total testosterone (TT) levels as the initial diagnostic test for androgen deficiency. However, it has been suggested that morning blood draw may not be necessary in older men due to a blunted circadian rhythm. We sought to determine whether it is possible to expand the morning sampling window for measurement of TT.

Research Design and Methods:

TT levels were measured in a subset of men (mean age of 61 years) participating in the 2013 Prostate Cancer Awareness Week.

Results:

TT levels measured in blood drawn from 8 to 11 AM (n = 229) differed significantly from those drawn outside this window (n = 442) (411.7 vs 368.3 ng/dl; p = 0.0003). Differences in TT levels were evident across five blood draw time windows (p = < 0.0001) and persisted after adjustment for age and BMI. TT levels in blood drawn from 2 to 5 PM (344.3 ng/dl) and 5 to 8 PM (334.4 ng/dl) differed significantly from that drawn from 8 to 11 AM (p < 0.05), while TT levels from 11 AM to 2 PM (396.5 ng/dl) and 8 PM to 8 AM (373.4 ng/dl) did not (p = 0.90 and 0.73, respectively).

Conclusion:

Based on these findings, it may be possible to expand the blood draw time window for measurement of serum TT. This community-based study was not prospectively design to determine the most appropriate blood draw window for TT measurement. Only a single TT measurement was made without consideration for day-to-day variability, and TT levels were not measured in the same men at different blood draw times.

Keywords: :

• Blood sampling
• Laboratory value
• Methodology
• Testosterone
• Testosterone level

Transparency

Declaration of funding

The study was supported by the Prostate Conditions Education Council. The analyses were performed by Eli Lilly and Company.

Declaration of financial/other relationships

A.N., D.A.P., S.A.D., S.G. and D.M. have disclosed that they are salaried employees at Eli Lilly and Company. E.D.C. has no relevant financial relationships with Eli Lilly and did not receive remuneration for his contribution to this paper. He has disclosed that he is a consultant for Bayer, Inc. MDx, Genomic He Jansen Pharmaceuticals, Dendreon, and Ferring Pharmaceuticals. W.P. has no relevant financial relationships with Eli Lilly and did not receive remuneration for her contribution to this paper. She has disclosed that she is a collaborator/contractor with MDx Health, Strand Diagnostics, Genomic Dx, Abbott Laboratories, and Bayer Inc.

CMRO peer reviewer 1 has disclosed that he is on the Board of the Prostate Conditions Education Council and owns stock in 3DBiopsy LLC. CMRO peer reviewer 2 has no relevant financial or other relationships to disclose.

Acknowledgment

Previous presentation: 97th Annual Endocrine Society Meeting, San Diego, CA, USA, 5–8 March, 2015.