Puberty is the maturational process of the reproductive endocrine system that results in final adult stature and adult body proportions, as well as final development of the genital organs and the capacity to reproduce. In this maturation of the hypothala-mic-pituitary-gonadal axis, the levels of gonadotropins increase and the production of sex steroids rise, leading to gonadal development and the development of secondary sexual characteristics. In boys, the first physical signs of puberty are an increase in testis volume and penis size, at a mean age of approx 11.5 yr in most Western countries. Testis volume increases from prepubertal values of 1-2 mL to 3-8 mL even before pubic hair appears, and reaches 20-30 mL in adulthood (1). Development of mature spermatogenesis is called spermarche (as opposed to menarche), at which time mature spermatozoa are found in the urine. This hallmark of gonadal maturation occurs at mean age of 13.5 years, when the mean testis volume reaches 11.5 mL (2).
From: Male Hypogonadism: Basic, Clinical, and Therapeutic Principles Edited by: S. J. Winters © Humana Press Inc., Totowa, NJ
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