Newborn circumcision is not associated with changes in adult penile sensitivity, according to a new study that provides preliminary evidence that the penile foreskin is not the most sensitive part of the penis.

A team led by Jennifer A. Bossio, a PhD candidate in clinical psychology at Queen’s University in Kingston, Ontario, studied 62 men aged 18–37 years: 30 circumcised and 32 not circumcised when they were newborns. Bossio and her colleagues used quantitative sensory testing protocols to assess touch and pain thresholds as well as warmth detection and heat pain thresholds at a control site (forearm) and 3–4 penile sites (glans penis,midline shaft, proximal to midline shaft, and, if present, the foreskin.

Results showed that penile sensitivity did not differ by circumcision status for any stimulus type of penile site, the investigators reported online ahead of print in The Journal of Urology. The authors noted that the foreskin of uncircumcised men was more sensitive to tactile stimulation than other penile sites, but this finding did not extend to any other stimuli.

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Bossio’s group pointed out that little is known about the sexual correlates of neonatal circumcision, penile sensitivity in particular. A widely accepted but largely untested hypothesis is that keratinization of the exposed glans penis epithelium occurs after circumcision, leading to decreased penile sensitivity, they noted. Another hypothesis is that removal of the highly innervated foreskin results in reduced penile sensitivity.

In an editorial comment accompanying the report by Bossio’s group, Ranjiv Mathews, MD, of the Southern Illinois University School of Medicine in Springfield, said he suspects the findings “will not placate those opposed to newborn circumcision.”

Dr. Mathews added that previous findings from a study published in BJU International (2007;99:864-869) of the foreskin being a source of significant sensation also are reason for concern. “Men circumcised in infancy have never had this added source of sensation and, therefore, may not be able to determine that sensitivity was lost.”