Serum testosterone (T) level variability in T gel-treated older hypogonadal men: Treatment monitoring implications

Ronald S. Swerdloff, Youngju Pak, Christina Wang, Peter Y. Liu, Shalender Bhasin, Thomas M. Gill, Alvin M. Matsumoto, Marco Pahor, Prasanth N Surampudi, Peter J. Snyder

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Context: The optimal frequency for on-treatment serum T measurement used for dose adjustment after transdermal T gel application isunknown,especially in oldermenwith thinner skinandslower metabolic clearance. Objectives: The objectives of the study was to determine the variability of postgel application serum T concentrations and assess whether single levels are reflective of average serum T concentrations over 24 hours (Cavg0-24). Design: This was a double-blinded, placebo-controlled randomized trial. Setting: The study was conducted at five academic centers. Participants: Forty-seven symptomatic men 65 years old or older with an average of two morning T concentration less than 275 ng/dL participated in the study. Intervention(s): Transdermal T or placebo gel was applied for 120 ± 14 days. Monthly dose adjustments were made if necessary to target serum T between 400 and 500 to 800 ng/dL. Main Outcome Measures: Variability of serumT 2 hours after the gel application on two outpatient visits and at multiple time points over 24 hours during the inpatient day was measured. Results: On-treatment T levels varied substantially on the 2 ambulatory days and over 24 hours during the inpatient day. Ambulatory 2-hour postapplication T levels did not correlate significantly with either 2-hour postapplication serum T or Cavg0-24 measured during the inpatient day. Only 22.2% of men receiving T had a Cavg0-24 within the target range of 500-800 ng/dL; 81.5% had a Cavg0-24 within the broader 300-1000 ng/dL range. Conclusion: Large within-individual variations in serum T after T gel application render ambulatory 2-hour postapplication T level a poor indicator of average serum T on another day. Our data point out the limitations of dose adjustments based on a single postapplication serum T measurement.

Original languageEnglish (US)
Pages (from-to)3280-3287
Number of pages8
JournalJournal of Clinical Endocrinology and Metabolism
Issue number9
StatePublished - Sep 1 2015

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Endocrinology
  • Clinical Biochemistry
  • Biochemistry, medical


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