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Puberty (cont.)

Physical Changes During Puberty

Secondary sex changes

For any child experiencing puberty, the most impressive evidence of the profound hormonal changes that are occurring center around the reproductive organs. This evolution commonly requires approximately five years from onset to completion. A series of predictable physical changes was noted and studied by several groups. In 1970, Dr. W.A. Marshall and Dr. J.M. Tanner published a landmark paper standardizing this sequence, and the series of changes have subsequently been known as the Tanner stages. These sequential stages of sexual maturity are listed below.

Tanner stages have been developed as a way to classify the time, course, and progress of changes that occur during puberty. They are based upon attainment of the so-called secondary sex characteristics, which include genital development in males, breast development in females, and pubic hair development in both genders.

Males

  • Tanner I: preadolescent
  • Tanner II: testicular enlargement and thinning of scrotal skin
  • Tanner III: penile enlargement and continued increase in testicular size
  • Tanner IV: further testicular/penile enlargement and appearance of pubic hair
  • Tanner V: adult testicular/penile size and pubic hair distribution

Females

  • Tanner I: preadolescent breast
  • Tanner II: breast tissue development with onset of areolar enlargement sparse longitudinal labial pubic hair
  • Tanner III: increase in breast tissue volume and areolar enlargement coarser and curlier pubic hair
  • Tanner IV: adult breast shape and elevation of the nipple thickening and broader distribution of pubic hair
  • Tanner V: mature adult breast shape and contour adult pubic hair character and distribution

The onset of puberty in males should take place between 9-14 years of age; females should experience the initial pubertal changes between 8-13 years of age. Precocious puberty is defined as the onset of the complete changes of puberty prior to these ages. Delayed onset of puberty implies lack of pubertal onset by the above timetable. There are several medical conditions (both physiologically normal and abnormal) that may give rise to problems with only adrenarche, pubarche, or thelarche.

Listed below is a table relating the physical changes and their age of onset as described by Marshall and Tanner. There exists a standard deviation of approximately one year. It is important to note that while some adolescents have a methodical step-by-step march through this period of their life, others seem to follow a much more erratic timetable of maturation.

Pubertal Event Mean Age of Onset for Boys Mean Age of Onset for Girls
Breast development N/A 11.2 years
Testicular enlargement 11.6 years N/A
Pubic hair development 13.4 11.7
Peak height velocity 14.1 12.1
Menarche N/A 13.5
Adult pubic hair configuration 15.2 14.4
Adult type breast N/A 15.3
Several principles are notable when reviewing this table: (1) the duration of puberty for both genders is approximately five years, (2) girls generally start puberty approximately one year ahead of boys, (3) peak height velocity indicates that time of maximal acquisition of height (the so called "growth spurt"), and (4) the onset of menstrual periods coincides with the slowing of rapid growth and is generally about two and a half years after the onset of puberty (Tanner II). Note that this growth spurt occurs in females during the earlier stages of pubertal events while occurring during the later stages of puberty in males. It is during this rapid height attainment in boys that a more muscular physique is established. As children, both genders have a growth velocity of 3-4 cm/year. At the maximum pubertal growth rate, boys have a greater velocity (10.3 cm/yr) than their female counterparts (9 cm/yr).
Medically Reviewed by a Doctor on 8/19/2014

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