Treatment Approach for Micropenis
Testosterone therapy should be the first-line treatment for micropenis, regardless of the underlying cause, to assess the penis's ability to respond and potentially achieve adequate length for normal urination, sexual function, and positive self-image.
Definition and Diagnosis
Micropenis is defined as a normally structured penis with a stretched length 2.5 standard deviations below the mean for age. In adults, this typically means a stretched penile length of less than 7.5 cm 1.
Key diagnostic steps:
- Use standard technique for stretched penile measurement
- Compare to age-appropriate nomograms
- Children above 1 year with stretched penile length <1.9 cm require evaluation 2
- Differentiate from buried penis or aphallia
Etiological Classification
Micropenis can be categorized based on underlying causes:
- Hypogonadotropic hypogonadism (hypothalamic or pituitary failure)
- Hypergonadotropic hypogonadism (testicular failure)
- Partial androgen insensitivity syndrome
- Idiopathic causes 2
Evaluation Process
- Complete medical, sexual, and surgical history
- Physical examination of genitalia and perineum
- Assessment of growth velocity (important for identifying hypothalamic/pituitary pathology)
- Laboratory tests:
- GnRH and/or hCG stimulation tests
- Chromosomal studies when indicated
- Evaluation of gonadotropic and testicular function during mini-puberty 3
Treatment Algorithm
1. First-Line Treatment: Testosterone Therapy
- Short course of testosterone should be tried in all patients with micropenis regardless of underlying cause 3, 2
- For infants/children: 3 intramuscular injections of testosterone enanthate (25 or 50 mg) at 4-week intervals 4
- Alternative for prepubertal children: Topical 5α-dihydrotestosterone gel 3, 2
2. At Puberty (If Ongoing Treatment Needed)
- Gradually increase testosterone dose to 200 mg monthly
- Later transition to adult replacement regimen 4
3. For Specific Underlying Conditions
- Hypopituitarism with GH deficiency: Appropriate hormonal therapy 3, 2
- Congenital hypogonadotropic hypogonadism: Continued testosterone replacement therapy
4. For Adults with Persistent Micropenis
- Conservative surgical techniques to improve length/girth (limited enhancement but fewer complications)
- Total phalloplasty using radial-artery-based forearm skin flaps for selected patients with realistic expectations 1
- Psychological counseling (essential component of management) 5
Treatment Outcomes and Prognosis
Research shows encouraging results with testosterone therapy:
- Studies of males with micropenis due to congenital pituitary gonadotropin deficiency showed that testosterone treatment in infancy/childhood followed by replacement therapy at puberty resulted in adult penile length within 2 SD of the mean 4
- Most testosterone-treated children achieve satisfactory gain in penile length and sexual function 2
- Six of eight men in a long-term study were sexually active with normal male gender identity and psychosocial behavior 4
Important Considerations and Caveats
- Surgical correction is generally not indicated for endocrine types of micropenis 2
- Sexual reassignment is rarely recommended in current practice 2
- Psychological support should be an integral part of management to alleviate distress and improve quality of life 5
- Patients with penile dysmorphic disorder require particularly careful and intensive psychological counseling 1
- Emerging tissue engineering techniques may offer future alternatives to penile replacement surgery 1