From the Guidelines
The evaluation of micropenis should start with a comprehensive physical examination, including the measurement and palpation of the penis, testes, and assessment of secondary sex characteristics, as recommended by the American Urological Association and American Society for Reproductive Medicine 1. The approach to evaluating micropenis involves several key steps, including:
- Accurate measurement of the stretched penile length and comparison to age-appropriate norms
- Detailed medical history focusing on prenatal exposures, family history of delayed puberty, and symptoms of endocrine disorders
- Physical examination to assess:
- Testicular size and position
- Presence of other genital abnormalities
- Signs of other congenital anomalies
- Body habitus and secondary sex characteristics, including hair distribution and breast development
- Laboratory evaluation, including measurement of testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and possibly karyotype analysis to identify potential chromosomal abnormalities The initial physical examination should include an assessment of the penis, including the location of the urethral meatus, as well as the measurement and palpation of the testes, and checking for the presence and consistency of the vasa and epididymides, as outlined in the recommendations by the American Urological Association and American Society for Reproductive Medicine 1. A digital rectal examination may also be necessary, as part of the comprehensive physical examination, to assess for any abnormalities of the reproductive structures. The evaluation should be guided by the most recent and highest quality evidence, and should prioritize the assessment of potential underlying causes of micropenis, such as hypogonadotropic hypogonadism, primary hypogonadism, androgen insensitivity, or other causes, to guide appropriate treatment strategies.
From the Research
Definition and Diagnosis of Micropenis
- Micropenis is defined as a structurally normal but abnormally small penis, with a stretched penile length (SPL) 2.5 SD below the mean for age and sexual stage 2.
- The appropriate cutoff for evaluation of micropenis as per international standards would be below 2 cm at birth and below 4 cm after 5 years of age 2.
- Micropenis should be differentiated from a buried or hidden penis and aphallia, and a standard technique of stretched penile measurement and nomograms for age should be used to identify children with micropenis 3.
Etiology and Classification of Micropenis
- The etiologies of micropenis include hypothalamo-pituitary disorders, genetic syndromes, partial gonadal dysgenesis, testicular regression, and disorders of testosterone biosynthesis and action 2.
- Micropenis can be classified into hypogonadotropic hypogonadism, hypergonadotropic hypogonadism, partial androgen insensitivity syndrome, and idiopathic groups based on etiology 3.
Evaluation and Treatment of Micropenis
- Evaluation of micropenis involves assessing basal and human chorionic gonadotropins (HCG)-stimulated gonadotropins, testosterone, dihydrotestosterone (DHT), and androstenedione levels, as well as karyotype assessment 2.
- Treatment aims to attain penile length sufficient for urination and sexual function, and may involve hormonal therapy with intramuscular or topical testosterone, topical DHT, or recombinant follicle stimulating hormone (FSH) and luteinizing hormone (LH) 2, 4.
- Surgical correction is limited and has variable patient satisfaction and complication outcomes, and is not indicated in common endocrine types of micropenis 3.
Long-term Follow-up and Management
- Long-term follow-up is necessary to assess adult stretched penile length and sexuality in patients with micropenis 5.
- Patients with micropenis may require long-term management from pediatric nurse practitioners, endocrinologists, urologists, pediatric surgeons, psychologists, and social workers 6.
- Further research is needed on the long-term outcomes of patients with micropenis, including the effects of treatment on adult penile length and sexual function 2, 6.