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Table of Contents | Abstract & Objectives | page 1 | page 2 | page 3
page 4 |page 5 |page 6 | page 7 |page 8 | page 9 | page 10
page 11 | References | Websites | Test
What triggers puberty is still unknown; however, there are distinct changes in the
hypothalamic-pituitary axis associated with the onset of puberty. These changes result in
an increase in gonadotropin-releasing hormone (GnRH), which stimulates increases in
leutenizing hormone (LH) and follicle stimulating hormone (FSH), hormones responsible
for the development of secondary sex characteristics. In males, LH stimulates
testosterone production and FSH stimulates gametogenesis. In females, LH stimulates
ovarian cells to produce androgens and progesterone and stimulates ovulation and FSH
increases estrogen production (Neinstein, 2002). Other hormones that effect puberty include thyroid hormones, growth hormones and insulin-like growth factors. Development of secondary sex characteristics is measured through the use of a Sexual
Maturity Rating (SMR) scale, sometimes called the Tanner scale. Because initiation and
rate of growth during adolescence are so variable, age is a poor indicator and predictor of
change. SMRs are essential in evaluating adolescents and provide a method to gauge
developmental progress, using a five-point scale of measurement. For females, ratings
measure breast development and pubic hair growth, and for males, they measure genital
development and pubic hair growth. Development of secondary sex characteristics
follows a general sequence over time. Alteration in this sequence may be an indication
of abnormal pubertal progression. As the age of onset of puberty varies, so too does the length of time in each stage. Female
pubertal development begins on average at 11.2 years of age (range 9.0 - 13.4) and lasts
about 4 years. Breast budding is most frequently the first physical sign of puberty.
Breast development and pubic hair development can progress at different rates and be at
different SMR levels at any given time. On average, the adolescent female's growth
spurt starts about one year before breast development begins. Peak height velocity is
reached about one year and one month after breast development begins. Menarche
typically occurs one year after peak height velocity is reached, usually at SMR 3 (19%)
or 4 (56%) at the average age of 12 years 4 months (range 9-17). See Table A for SMR
parameters of female breast and pubic hair development (Tanner, 1962). Although it has been noted that the mean age for onset of secondary sex characteristics has decreased in girls, the overall effect on mean age at initiation of menstruation has only decreased by six months and only in girls of African-American ethnicity (Neinstein, 2002). Male pubertal development begins on average at 11.6 years of age (range 9.5 - 13.5).
Testicular enlargement is most commonly the first physical sign of puberty in males.
SMR levels for pubic hair development and genital development (testes, scrotum and
penis) can differ at any given time in the same individual. See Table A for male SMR parameters. The average length of time for completion of puberty in males is three years.
Spermarche usually occurs early in puberty during SMR 2.5 (Tanner, 1962).
Secondary Sexual Development
| Table A. Sexual Maturity Rating - Girls & Boys*
Female |
|
| Breast | Pubic Hair |
| No development | No pubic hair |
| Breast bud, areola widens | Long, slightly pigmented, straight hair along labia |
| Breast larger, more elevation
Extends beyond areolar parameter |
Increased in quantity, darker, more curly and coarser, present in typical female triangle |
| Breast larger and more elevation
Areola and papilla form a mound projecting from the breast contour |
Hair more dense, curled and adult in distribution but in a smaller quantity |
| Breast adult appearance
Areola and breast in same plane, with papilla projecting above areola |
Abundant, adult-type pattern
Hair extends to medial aspect of thigh |
| Male | ||
| Testes and Scrotum | Penis | Pubic Hair |
| Testicular volume - less than 1.5ml | Childlike | None |
| Testicular volume - 1.6 - 6ml, Scrotum reddened, thinner, larger | No change | Light, downy hair laterally |
| Testicular volume - 6-12ml, Scrotum - great enlargement | Increased length | Extended across pubis |
| Testicular volume - 12-20ml, Scrotum - further enlargement | Increased length and circumference | More abundant with curling and darkening |
| Testicular volume - >20 ml
Scrotum - adult appearance |
Adult male appearance | Adult quantity and distribution with hair present on inner thighs |
| *Ratings for each developmental characteristic may differ in the same individual at one point in time (Tanner, 1962). | ||
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