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- What are the causes of isolated micropenis?
Micropenis is defi ned as stretched penile length <−2.5SD for that particular
age. In a term newborn, stretched penile length <2.5 cm is used to defi ne
micropenis. Isolated micropenis (without any genital ambiguity) suggests
impaired androgen synthesis/action or GH defi ciency. The causes include
hypogonadotropic hypogonadism, hypergonadotropic hypogonadism, andro-
gen biosynthetic defect, androgen insensitivity syndrome, and neonatal GH
defi ciency. The normal values of stretched penile length at various stages of
life are summarized in the table given below.
Stretched penile length in normal males ( cm )Age Mean ± SD (cm)Micropenis
(mean-2.5 SD, cm)
Newborn: 30 weeks 2.5 ± 0.4 1.5
Newborn: 34 weeks 3.0 ± 0.4 2.0
Newborn: term 3.5 ± 0.4 2.5
0–5 months 3.9 ± 0.8 1.9
6–12 months 4.3 ± 0.8 2.3
1–2 years 4.7 ± 0.8 2.6
2–3 years 5.1 ± 0.9 2.9
3–4 years 5.5 ± 0.9 3.3
4–5 years 5.7 ± 0.9 3.5
5–6 years 6.0 ± 0.9 3.8
6–7 years 6.1 ± 0.9 3.9
7–8 years 6.2 ± 1.0 3.7
8–9 years 6.3 ± 1.0 3.8
9–10 years 6.3 ± 1.0 3.8
10–11 years 6.4 ± 1.1 3.7
Adult 13.3 ± 1.6 9.3
Adapted from Indian Journal of Pediatrics. 2000;67:455–60
- What is the difference between the terms “ microphallus ” and “ micropenis ?”
The term “micropenis” should be preferred when stretched penile length is
<−2.5SD for that particular age in the presence of palpable testes and normal
location of urethral meatus without any genital ambiguity. Patients with iso-
lated micropenis should be evaluated for hypogonadism, growth hormone defi -
ciency, and DSD. The term (micro)phallus should be preferred in patients who
have genital ambiguity and/or absence of palpable testes and these patients
require evaluation for DSD (Fig. 9.7 ).9 Disorders of Sex Development