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The most accurate measurement of the human penis comes from several measurements at different times since there is natural minor variability in size due to arousal level, time of day, room temperature, frequency of sexual activity, and reliability of measurement. When compared to other primates, including large primates such as the gorilla, the human penis is thickest, both in absolute terms and relative to the rest of the body. Measurements vary, with studies that rely on self-measurement reporting a significantly higher average than those with staff measuring. , a systematic review of the best research to date on the topic has concluded that the mean length of an erect human penis is approximately . Flaccid penis length is a poor estimate of erect length. Most of human penis growth happens between infancy and the age of five, and between about one year after the onset of puberty and, at latest, approximately 17 years of age. A statistically significant correlation between penis size and the size of other body parts has not been found in research. Some environmental factors in addition to genetic, such as the presence of endocrine disruptors, can affect penis growth. An adult penis with an erect length of less than , but otherwise formed normally, is referred to in medicine as a micropenis. Penis size is positively correlated with increasing testosterone levels during puberty. However, after puberty, administration of testosterone is not capable of affecting penis size, and androgen deficiency in adult men only results in a small decrease in size.〔 Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are also involved in penis size, with deficiency (e.g., that observed in growth hormone deficiency or Laron syndrome) at critical developmental stages having the potential to result in micropenis (very small penis size). ==History== Perceptions of penis size are culture-specific. In Ancient Greece and in Renaissance art, an uncircumcised and small penis was culturally seen as desirable in a man, whereas a bigger or circumcised penis was viewed as comical or grotesque. Ancient Rome may have had a contrary view, and a larger penis size was preferred in medieval Arabic literature. Males may quite easily underestimate the size of their own penis relative to that of others, and many men who believe that their penis is of inadequate size have average-sized penises. The perception of having a large penis is often linked to higher self-esteem. Fears of shrinking of the penis in folklore have led to a type of mass hysteria called penis panic, though the penis legitimately can shrink in size due to scar tissue formation in the penis from a medical condition called Peyronie's disease.〔(Peyronie's disease ). Mayo Clinic〕 Marketers of penis enlargement products exploit fears of inadequacy, but there is no consensus in the scientific community of any non-surgical technique that permanently increases either the thickness or length of the erect penis that already falls into the normal range. 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「Human penis size」の詳細全文を読む スポンサード リンク
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