Cut-offs for stretched penile length in neonates

Sir,

We read with interest the recently published paper by Prabhu et al. titled, “Normative data for stretched penile length in term neonates born in Tamil Nadu”.[1] The attempt to establish local norms for stretched penile length (SPL) in neonates is noteworthy in view of racial and ethnic variations worldwide.[2] However, the usefulness of their data in a clinical practice is limited in the absence of defined cut-off of SPL measurements. We believe that some re-evaluation of the available data will significantly improve the clinical utility of their findings.

The clinical utility of SPL measurements in neonates depends upon the ability to define micropenis or macropenis based on the published normative data. A finding of micropenis in a neonate is an important clinical clue to numerous underlying disorders associated with pituitary/hypothalamic failure, primary testicular failure, defects in testosterone action as well as some syndromes.[2] Similarly, macropenis may lead to the identification of rare syndromes like Lenz microphthalmia syndrome and Beckwith–Wiedemann syndrome.[3] The definition of micro or macropenis is based on SPL of 2.5 standard deviation (SD) below or above the mean for age respectively.[2] Alternatively, 3^rd and 97^th percentile values can be used.[4] In this context, it is important to establish a range, lower (−2.5 SD) and upper (+2.5 SD) cut-offs or lower (3^rd) and upper (97^th) centiles of the SPL measurements. Methods used in previous studies on normative data may be applied to the available data to establish the cut-off values.[4,5] These can then be supplied as supplementary data files in a forthcoming issue of Indian Journal of Endocrinology and Metabolism.