Lawrence S. Neinstein, M.D., F.A.C.P.
Professor of Pediatrics and Medicine
USC Keck School of Medicine
Executive Director
University Park Health Center
Associate Dean of Student Affairs
   

 

 

Puberty - Normal Growth and Development (A1)

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To assess growth and development during puberty it is critical to evaluate sexual maturity ratings as these correlate to normal growth and also physiologic changes. Sexual maturity ratings include breast development in females, genital development in males and pubic hair development in both males and females.

KEY HORMONES

Many of the body's hormones influence growth, such as growth hormone, thyroxine, insulin, and corticosteroids (all of which influence growth rate), leptin (which alters body composition), and parathyroid hormone, 1,25-dihydroxy-vitamin D, and calcitonin (all of which affect skeletal mineralization). However, the key hormone in growth is GH which is mediated by growth hormone-releasing hormone (GHRH) and somatostatin (SS). Growth hormone secretion is increased by GHRH and decreased by somatostatin. Both growth hormone levels and IGF-I (somatomedin-C) levels rise during puberty. The increase is most marked during mid and late puberty and correlates best with pubertal stage, bone age, and time from peak height velocity (PHV).

The maturation of bones is influenced by thyroid hormones, adrenal androgens, and gonadal sex steroids, mainly estrogen. An excess secretion of these hormones can lead to advanced bone maturation, and at the time of puberty, deficiency causes delay.

At puberty, both sex steroids and growth hormone participate in the pubertal growth spurt. The ending of the growth spurt is secondary to epiphyseal closure, due to the action of the sex steroids.

An increase in physical size is a universally recognized event of puberty. Average growth velocities decrease from the first year of life until puberty from 25 cm/year during the first year of life to 5-6 cm/year during years 5 to 10. During puberty height velocity increases and peaks during the adolescent growth spurt. Landmarks include:

HEIGHT

The beginning of the increase in growth velocity is about age 11 in boys and 9 in girls but varies widely from individual to individual.

The peak height velocity occurs at a mean of 13.5 years in boys and 11.5 years in girls.

Pubertal growth accounts for about 20% of final adult height, a total averaging 23-28 cm in females and 26-28 cm in males.

The average growth spurt lasts 24-36 months.

Growth during the year of PHV in the normal female averages 9 cm/yr and varies normally from 5.4 cm to 11.2 cm. In the normal male, the PHV averages 10.3 cm/yr and varies normally from 5.8 cm to 13.1 cm.

Males on average are 12-13 cm taller than females primarily because of the 2-year delay in bone closure as compared to females. This accounts for about a 10-cm difference between the two sexes; in addition, males also have 2-3 cm more of growth during their growth spurt.

WEIGHT

Weight velocity increases and peaks during the adolescent growth spurt.

Pubertal weight gain accounts for about 50% of an individual's ideal adult body weight.

The onset of accelerated weight gain and the peak weight velocity (PWV) attained are highly variable. (Normal weight for age percentile curves are available through the Centers for Disease Control and Prevention, 6525 Belcrest Road , Hyattsville , MD 20782-2003 . They can also be obtained on the CDC website at: www.cdc.gov/growthcharts/ .

Differences in Growth Spurts between Males and Females

PHV occurs about 18-24 months earlier in the female than in the male.

PHV in females averages 2 cm/yr less than in males.

PWV coincides with PHV in males, but PWV occurs 6-9 months after PHV in females.

Prediction of Mature Height

While predicting adult height is a difficult task, individuals have used both the bone age in calculations or a measure using midparental height as most individuals have an adult height that is within 2 inches of the midparental height. This is calculated using:

For girls:

(father's height - 13 cm) + mother's height
2

For boys:

(father's height + 13 cm) + mother's height
2

BODY COMPOSITION

BODY MASS INDEX

Body Mass Index (BMI) is an important measure for assessment of appropriate weight for height

BMI is determined as follows:

Metric Formula:

Weight in kilograms ÷ height in meters ÷ height in meters = BMI

English Formula:

Weight in pounds ÷ by height in inches ÷ height in inches X 703 = BMI

The BMI declines until ages 4-6 years and gradually increases through adolescence and adulthood. Children with an earlier increase in BMI are more likely to have increased BMIs in adulthood. BMI tables can be obtained from the National Center for Chronic Disease Prevention and Health Promotion ( www.cdc.gov/growthcharts/)

Lean Body Mass

Lean body masses decreases in females from about 80% to 75% at maturity while in males it increases from about 80% to about 90% at maturity due to an increase in skeletal muscle mass. In females the percentage of body fat increases.

Skeletal Mass

The increase in skeletal muscle mass during puberty is critical and peak bone mass is achieved by early adulthood (the lifetime "bone bank"). Epiphyseal maturation occurs under the influence of estradiol and testosterone. The assessment of this skeletal maturation (bone age) is an excellent index of physiological maturation and assessment of growth potential.

Assessment of sexual maturity ratings are listed below:

  • Males
    • Genital stage 1 (G1) : Prepubertal
      • Testes: Volume less than 1.5 mL
      • Phallus: Childlike
    • Genital Stage 2 (G2)
      • Testes: Volume 1.6-6 mL
      • Scrotum: Reddened, thinner, and larger
      • Phallus: No change
    • Genital Stage 3 (G3)
      • Testes: Volume 6-12 mL
      • Scrotum: Greater enlargement
      • Phallus: Increased Length
    • Genital Stage 4 (G4)
      • Testes: Volume 12-20 mL
      • Scrotum: Further enlargement and darkening
      • Phallus: Increased length and circumference
    • Genital stage 5 (G5)
      • Testes: Volume more than 20 mL
      • Scrotum and phallus: Adult
  • Females
    • Breast stage 1 (B1)
      • Breast: Prepubertal; no glandular tissue
      • Areola and papilla: Areola conforms to general chest line
    • Breast stage 2 (B2)
      • Breast: Breast bud; small amount of glandular tissue
      • Areola: Areola widens
    • Breast stage 3 (B3)
      • Breast: Larger and more elevation; extends beyond areolar parameter
      • Areola and papilla: Areola continues to enlarge but remains in contour with the breast
    • Breast stage 4 (B4)
      • Breast: Larger and more elevation
      • Areola and papilla: Areola and papilla form a mound projecting from the breast contour
    • Breast stage 5 (B5)
      • Breast: Adult (size variable)
      • Areola and papilla: Areola and breast in same plane, with papilla projecting above areola
  • Male and female: pubic hair
    • Pubic hair stage 1 (PHI)
      • None
    • Public hair stage 2 (PH2)
      • Small amount of long, slightly pigmented, downy hair along the base of the scrotum and phallus in the male or the labia majora in females; vellus hair versus sexual type hair (PH3)
    • Pubic hair stage 3 (PH3)
      • Moderate amount of more curly, pigmented, and coarser hair, extending more laterally
    • Pubic hair stage 4 (PH4)
      • Hair that resembles adult hair in coarseness and curliness but does not extend to medial surface of thighs
    • Pubic hair stage 5 (PH5)
      • Adult type and quantity, extending to medial surface of thigths

Sexual Maturity Ratings: female pubic hair stages

MALE SEXUAL DEVELOPMENT

Male sexual development generally begins with the attainment of stage G2, at an average age of 11.6 years (range 9.5-13.5 years). The first physical sign of puberty in 98% of males is testicular enlargement. Ejaculation often occurs during SMR3 while SMR4 is often associated with fertility but may occur during SMR3. Puberty takes about 3 years to complete but may range from 2 to 5 years. The typical sequence of pubertal events in males is seen below which demonstrates the usual late occurrence of peak height velocity at an average SMR of 4. The typical sequence is adrenarche, beginning of growth spurt, testicular development, beginning of pubic hair, peak height velocity

Sequence of pubertal events in males:
Sequence of pubertal events in males
click for full-size image

FEMALE SEXUAL DEVELOPMENT

In most females, the beginning of a breast bud is the first physical sign of puberty. While the traditional mean age of female sexual development was in the early 11s, over the past decade in developed countries, this age has been decreasing. For example, in the United States , the mean age of onset of breast development is 8.87 years for African-American girls and 9.96 years for white girls. The mean ages for the onset of pubic hair are 8.78 years and 10.51 years, respectively. Potential reasons for this decrease in age of onset, while unknown, might include improved nutrition, increasing obesity, hormonal exposures and other environmental/societal alterations. There may be important future consequences of earlier maturation with regards to teen behavior, sexual activity and pregnancy as well as future lifetime health consequences of early sexual maturation such as potential increase risk of breast cancer.

During puberty, the female's breasts develop and the ovaries, uterus, vagina, labia, and clitoris increase in size. The uterus and ovaries increase in size fivefold to sevenfold. Completion of puberty in females averages 4 years but can range from 1.5 years to 8 years. In the average adolescent female, the growth spurt starts about 1 year before breast development and this is followed by an average of 1.1 years until PHV and then followed in an average of 1 year by menarche. The typical sequence of pubertal events in females is seen below which demonstrates the usual early occurrence of peak height velocity at an average SMR of 2 and the late occurrence of menarche at an average SMR of 4. Menarche occurs in 19% of adolescents during PH3 and in 5 6% during PH4. There is little or no correlation between adult height and either age of onset of growth spurt, age of PHV, velocity at peak, or pubertal height gain. However, there is a correlation between adult height and the height at onset of growth spurt or height at PHV.

Sequence of pubertal events in females
Sequence of pubertal events in females
click for full-size image

There are wide variations of puberty between individuals and these are discussed in B1.

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Questions

Question #1
What is the first visible sign of puberty in males?

Answer #1
The first visible sign of puberty in males is an increase in testicular size. However, an increase in height velocity occurs before this although this is unlikely to be noticed in routine growth chart.


Question #2
What is the first visible sign of puberty in females?

Answer #2
Increase in breast development.


Question #3
The following male is about what stage of pubic hair?

What stage of pubic hair?
click for full-size image

Answer #3
Stage 3 since there is a scant amount of ADULT hair. In stage II, there is sparse amount of fine non-adult hair. In stage four seen below there is normal adult hair but not quite out to medial thigh. Review of sexual maturity ratings.

Stage of pubic hair
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Question #4
What breast stage is indicated below?

Breast stage
click for full-size image

Answer #4
Stage 4. In stage two there is small breast bud and in stage 3 there is larger and more elevation of breast and areola enlarges but remains in contour with breast. In the photo above, there is a secondary mound and this places this teen in stage four. In stage 5, which some females never attain, the areola flattens out


Question #5
Peak height velocity is an early or late event in most females?

Answer #5
In males PHV is usually a late pubertal event at about an SMR of 4 but in females, PHV is usually occurs earlier during puberty. In females PHV is most common during SMR 2 while menarche occurs in about 2/3rds of females at about SMR 4.


Question #6
Most of the difference between the height of males and females is because the PHV in males is greater? True or false?

Answer #6
False: About 80% of the difference between male and female height is the later age of PHV in males which allows for greater growth before epiphyseal closure. The difference in amount of PHV between males and females is probably responsible for about 20% of the difference.


Question #7
In developed countries, it appears that there has been a reversal of the earlier onset of female puberty and so the average age of the start of sexual development has increased by about 6 months? True of false?

Answer #7
False: In developed countries the onset of female sexual development has continued to decrease in age.

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Cases

Case #1
A fourteen-year-old adolescent male comes to see you in the office. The teen complains of fatigue for about six months with no other symptoms. His psychosocial profile and history is normal. His examination is normal with no focal abnormal signs. You order a CBC and his hemoglobin is 12.0 gm/DL.

Is this teen anemic and do you have an explanation for his fatigue.

Answer:
This is a bit of a "trick" question as you really cannot answer the question without first knowing the sexual maturity rating of the adolescent.

SMR Stages
click for full-size image

The three teens above are all fourteen years of age. The one on the left is about a SMR of 2, the middle about a 3 and the one on the right a 4 to 5. All three of these teens are normal for age 14. However, there is a significant correlation between SMR and hemoglobin/hematocrit levels in pubertal males. In males, with increasing SMR, there is an increase in testosterone and thus an increase in erythropoietin levels. The rising erythropoietin levels increase both skeletal muscle mass and also increase hemoglobin production. Thus, a normal hemoglobin level for the teen on the far left above might be in the 12.0 - 14.0 gm/dl while a normal level for the teen on the right might be in the 14.0 -18.0 gm/dl level. A hemoglobin level of 12.0 would be normal for a teen in early development but anemic for a teen in near adult development. In conclusion, for the teen on the left, the blood count cannot explain the teen's fatigue while for the teen on the right, it is an indication of some abnormality that needs further evaluation.


Case #2:
Your next teen in the morning clinic gives you a history of feeling well but is being referred from an outside clinic for an abnormal blood test. His history is completely negative as well as his psychosocial history. The teen comes in with laboratory from an outside physician that shows a normal CBC and normal chemistry panel with the exception of an alkaline phosphatase that is about 50% above normal. On examination, there are no abnormal findings and the teen is a SMR of four. Are you concerned?

Answer:
This is a common occurrence in developing adolescents. With rapid bone growth, alkaline phosphatase levels increase and one can find a level that might be 50-100% above the normal range. This tends to peak at about the peak height velocity in males and females so occurs earlier in females. The graph below demonstrates this relationship between alkaline phosphatase levels and SMR in both males and females.

Serum Alkaline Phosphate Level
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How would you expect this teens body composition (body fat, skeletal muscle mass) to compare to a female also age 14 and SMR of 4.

Of note is that males and females have opposite affects of puberty on muscle mass and body fat. In males, under the influence of testosterone, skeletal muscle mass increases and percent body fat decreases as seen in the graph below. In a female, under the influence of testosterone, body fat increases. Thus in this teen one might expect a per cent body fat of about 11% in a healthy male and over 20% in a healthy female of SMR 4.

Percent Body Fat Correlated to SMR
click for full-size image

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Web Sites

For Teenagers and Parents

http://www.puberty101.com/
Information site on puberty and other adolescent questions

http://www.iwannaknow.org/puberty.html
Information on puberty from American Social Health Association

http://www.healthychildren.org/English/ages-stages/gradeschool/puberty/pages/Whats-Happening-to-my-Body.aspx
Information on puberty handout from American Academy of Pediatrics

http://www.plannedparenthood.org/health-topics/teens/having-your-period-4320.htm
Information from Planned Parenthood for girls on puberty and menstruation

http://www.kidshealth.org/teen/sexual_health/
Information from kidshealth web site on puberty

http://www.plannedparenthood.org/info-for-teens/our-bodies/puberty-guys-33806.htm
What happens during puberty for guys from Planned Parenthood

http://www.webwinds.com/yupanqui/apachesunrise.htm
Description of the Apache sunrise ceremony for puberty in girls.

http://www.keepkidshealthy.com/adolescent/puberty.html
Teen health site, puberty section

http://teenhealth.about.com/od/physicalhealth/a/pubertyqanda.htm
Teen Health article on puberty

http://www.youngwomenshealth.org/menstrual.html
From Young Womens Health Center at Boston Childrens on Puberty

For Health Professionals

http://www.cdc.gov/growthcharts
Growth charts on line

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References

Neinstein LS and Kaufman FR, chapter 1: Normal Physical Growth and Development from Neinstein L.S. Adolescent Health Care: A Practical Guide, 4th edition,

Lippincott Williams and Wilkins 2002.

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Copyright (©) 2004-2013 Lawrence S. Neinstein, University of Southern California . All rights reserved. Republication or redistribution of the text, table, graphs and photos is expressly prohibited. The University of Southern California shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon.