CONGENITAL ANOMALIES OF THE PENIS
Congenital absence of the penis (apenia) is extremely rare. In this condition, the urethra generally opens on the perineum or inside the rectum. The child should undergo a karyotype and referral to a disorders of sexual differentiation (DSD) specialist.
Megalopenis is characterized by rapid enlargement of the penis during childhood in boys with abnormalities that increase the production of testosterone. Examples of these abnormalities are interstitial cell tumors of the testicle, hyperplasia, or tumors of the adrenal cortex. Management is by correction of the underlying endocrine problem.
Micropenis is a more common anomaly and has been attributed to a testosterone deficiency that results in poor growth of organs that are targets of this hormone. A penis smaller than 2SD (standard deviations) from the norm is considered a micropenis (see Table 41–1). The testicles are small and frequently undescended. Other organs, including the scrotum, may be involved. Early evidence suggests that the ability of the hypothalamus to secrete luteinizing hormone-releasing hormone (LHRH) is decreased. The pituitary–gonadal axis appears to be intact, since the organs respond to testosterone, although this response may be sluggish at times. Studies have shown that topical application of 5% testosterone cream causes increased penile growth, but its effect is due to absorption of the hormone, which systemically stimulates genital growth. Patients with micropenis must be carefully evaluated for other endocrine and central nervous system (CNS) anomalies. Retarded bone growth, anosmia, learning disabilities, and deficiencies of adrenocorticotropic hormone and thyrotropin have been associated with micropenis. In addition, the possibility of DSD problems must be carefully investigated before therapy is begun.
Table 41–1.Size of unstretched penis and testis from infancy to adulthood. |Favorite Table|Download (.pdf) Table 41–1. Size of unstretched penis and testis from infancy to adulthood.
|Age (years) ||Length of penis (cm ± SD) ||Diameter of testis (cm ± SD) |
|0.2–2 ||2.7 ± 0.5 ||1.4 ± 0.4 |
|2.1–4 ||3.3 ± 0.4 ||1.2 ± 0.4 |
|4.1–6 ||3.9 ± 0.9 ||1.5 ± 0.6 |
|6.1–8 ||4.2 ± 0.8 ||1.8 ± 0.3 |
|8.1–10 ||4.9 ± 1 ||2 ± 0.5 |
|10.1–12 ||5.2 ± 1.3 ||2.7 ± 0.7 |
|12.1–14 ||6.2 ± 2 ||3.4 ± 0.8 |
|14.1–16 ||8.6 ± 2.4 ||4.1 ± 1 |
|16.1–18 ||9.9 ± 1.7 ||5 ± 0.5 |
|18.1–20 ||11 ± 1.1 ||5 ± 0.3 |
|20.1–25 ||12.4 ± 1.6 ||5.2 ± 0.6 |
The approach to management of micropenis has undergone gradual change in recent years, but androgen replacement is the basic requirement. The objective is to provide sufficient testosterone to stimulate penile growth without altering growth and closure of the epiphyses. A regimen of 25 mg orally every 3 weeks for no more than four doses has ...