Matthew Spitzer, MD; Shehzad Basaria, MD; Thomas G. Travison, PhD; Shalender Bhasin, MD
Potential Conflicts of Interest: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M12-0805.
Spitzer M, Basaria S, Travison TG, Bhasin S. Effects of Testosterone Replacement on Response to Sildenafil Citrate. Ann Intern Med. 2013;158:570-571. doi: 10.7326/0003-4819-158-7-201304020-00019
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Published: Ann Intern Med. 2013;158(7):570-571.
We agree with Dr. Smoger's comment that testosterone measurements vary because of multiple factors, including assay variation, diurnal and pulsatile secretory rhythms, and variations in sex hormone–binding globulin levels. We measured testosterone between 7:30 and 10:00 a.m. by liquid chromatography–tandem mass spectrometry, which is widely considered the reference method with the highest sensitivity and specificity. However, we concur that additional measurements of testosterone during screening would have been valuable.
Obesity is associated with decreased sex hormone–binding globulin, and we agree that it might have played some role in the low levels of total testosterone (1). As such, we included participants with total testosterone levels less than 11.45 nmol/L (330 ng/dL) or free testosterone levels less than 173.35 pmol/L (50 pg/mL), which are well below the reference ranges established in healthy young men by using liquid chromatography–tandem mass spectrometry (2).
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