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Micropenis is an unusually small penis. A common criterion is a dorsal (measured on top) erect penile length of at least 2.5 standard deviations smaller than the mean human penis size, or smaller than about for an adult when compared to an average erection of .〔ScienceDaily.com (2004). "(Surgeons Pinch More Than An Inch From The Arm To Rebuild A Micropenis )," 6 Dec. 2004, URL accessed 2 April 2012.〕 The condition is usually recognized shortly after birth. The term is most often used medically when the rest of the penis, scrotum, and perineum are without ambiguity, such as hypospadias. Micropenis occurs in about 0.6% of males.〔 ==Causes== Of the abnormal conditions associated with micropenis, most are conditions of reduced prenatal androgen production or effect, such as abnormal testicular development (testicular dysgenesis), Klinefelter syndrome, Leydig cell hypoplasia), specific defects of testosterone or dihydrotestosterone synthesis (17,20-lyase deficiency, 5α-reductase deficiency), androgen insensitivity syndromes, inadequate pituitary stimulation (gonadotropin deficiency), and other forms of congenital hypogonadism. Micropenis can also occur as part of many genetic malformation syndromes that do not involve the sex chromosomes. It is sometimes a sign of congenital growth-hormone deficiency or congenital hypopituitarism. Several homeobox genes affect penis and digit size without detectable hormone abnormalities. In addition, in utero exposure to some estrogen based fertility drugs like diethylstilbestrol (DES) has been linked to genital abnormalities and/or a smaller than normal penis. After evaluation to detect any of the conditions described above, micropenis can often be treated in infancy with injections of various hormones, such as human chorionic gonadotropin and testosterone. Most eight- to fourteen-year-old boys referred for micropenis do not have the micropenis condition. Such concerns are usually explained by one of the following: # a penis concealed in suprapubic fat (extra fat around the mons pubis). # a large body and frame for which a prepubertal penis simply appears too small. # delayed puberty with every reason to expect good future growth. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Micropenis」の詳細全文を読む スポンサード リンク
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