What is the treatment approach for a patient with micropenis?

Treatment Approach for Micropenis

The primary treatment for micropenis is testosterone therapy, which should be initiated early in infancy or childhood to achieve adequate penile growth and preserve normal sexual function. 1

Definition and Diagnosis

• Micropenis is defined as a structurally normal but abnormally small penis with a stretched penile length (SPL) of 2.5 standard deviations below the mean for age and sexual development stage 2
• Diagnostic criteria include SPL below 2 cm at birth and below 4 cm after 5 years of age 2
• Ultrasound of the genitalia should be performed to assess for associated abnormalities 3
• Micropenis must be differentiated from buried penis, hidden penis, and aphallia using standard measurement techniques 4

Etiology Assessment

• Evaluate for underlying causes through a systematic approach:
  • Hypogonadotropic hypogonadism (hypothalamic or pituitary failure) 4
  • Hypergonadotropic hypogonadism (testicular failure) 4
  • Partial androgen insensitivity syndrome 4
  • Idiopathic causes 4
• Laboratory evaluation should include:
  • Basal and hCG-stimulated gonadotropins (FSH, LH) 2
  • Testosterone, dihydrotestosterone (DHT), and androstenedione levels 2
  • Karyotype assessment to rule out disorders of sex development (DSD) 2
• Growth velocity assessment to identify associated hypothalamic or pituitary pathology 4

Treatment Algorithm

First-Line Treatment: Hormonal Therapy

• Regardless of underlying etiology, a trial of testosterone therapy should be initiated to assess penile response 5, 4
• Treatment options include:
  1. Intramuscular testosterone enanthate:
     • 25-50 mg given as 3 injections at 4-week intervals in infancy or early childhood 1
     • Optimal timing is during the second and third months of life 6
  2. Topical testosterone preparations 5
  3. Topical 5α-dihydrotestosterone (DHT) gel, which has shown effectiveness in prepubertal children 5, 4
  4. Recombinant FSH and LH therapy in selected cases 2

Treatment Outcomes and Monitoring

• Short courses of testosterone therapy in infancy and childhood can augment penile size into the normal range 1
• Continued testosterone replacement therapy at puberty can result in adult penile size within 2 standard deviations of the mean 1
• Studies show that most testosterone-treated children achieve satisfactory gains in penile length and sexual function 4
• Long-term follow-up is essential to assess final adult penile length achieved following treatment 2

Special Considerations

• Sex reassignment is rarely indicated in endocrine causes of micropenis 4
• Surgical intervention has limited role with variable patient satisfaction and complication rates 2
• Surgical elongation techniques (Hinman or Johnston) may be considered in cases with poor or absent androgen response, but should be performed by experienced pediatric urologists 6
• Psychological counseling is often necessary and helpful for both the patient and family 5

Important Clinical Pearls

• Early diagnosis and treatment are crucial for optimal outcomes 5, 4
• Multiple studies demonstrate that testosterone treatment does not impair future penile growth during adolescence or compromise adult penile length 1
• Children with associated hypopituitarism and growth hormone deficiency require appropriate hormonal replacement therapy 5, 4
• The primary goal of treatment is to achieve sufficient penile length for normal urination, sexual function, and positive self-body image 5, 2