Background Micropenis, defined as a penile length more than 2.5 standard deviations below the mean for age and population, presents significant concerns for patients and parents. Despite current guidelines recommending multidisciplinary management, there is limited evidence on long-term outcomes, particularly in untreated patients.

Methods This retrospective cohort study involved 46 male children aged 7 to 9 years presenting with micropenis at the Ali Asghar Endocrine Clinic from 2015 to 2023. Initial penile size, BMI, and other growth parameters were measured, with biannual follow-ups extending three years post-bone fusion to evaluate growth rates and influential factors.

Results Initial mean stretched penile length (SPL) was 3.22 ± 0.21 cm. Significant increases in penile size were observed across all intervals, with the highest growth rates occurring between the first- and second-years post-fusion. BMI emerged as the most significant predictor of penile growth, while initial SPL was the least influential factor. By the third-year post-fusion, all subjects achieved penile lengths within the normal range.

Conclusion Our findings indicate that most untreated micropenis patients attain normal penile size by adulthood, highlighting the importance of monitoring growth rates rather than focusing solely on initial penile size. This study provides critical insights for developing guidelines and management strategies for micropenis, emphasizing the necessity of continued follow-up to ensure optimal outcomes.

The authors have declared no competing interest.

This study did not receive any funding.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The protocol for this study was reviewed and approved by the Ethical Institutional Review Board of Iran University of Medical Sciences (approval number: 05-2024-155).

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All data produced in the present study are available upon reasonable request to the authors.