What Is the Medical Definition of Puberty?
What Happens to a Girl's Body During Puberty? What Does Puberty Mean for a Boy?
What Are the First Signs of Puberty?
What Are the Stages of Puberty?
What is Precocious Puberty?
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.
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 |
|---|---|---|
| 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). | ||
| 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 |
In females, approximately 50% of lifetime total body calcium is deposited into bones during puberty. In males, 50%-65% of lifetime total body calcium is laid down, with males having approximately 50% more total body calcium than females. A woman's maximal calcium deposition in bones occurs during the first half of puberty. Studies have also demonstrated that both genders first experience an increase in bone width followed by mineralization with calcium. Such a disparity between increase in size of bone and strength of bone may explain an increase in bone fractures during adolescence. The importance of calcium intake via dairy products and other sources to maximize bone calcification must be underscored to teenagers, some of whom may adopt fad diets or weight-loss regimens.
Both genders gain weight due to somatic growth and bone mineralization as described above. Early pubertal changes in boys demonstrate a reduction of fat mass which is followed during the last one-third of puberty by an acquisition of muscle mass. In adolescent girls, the majority of weight gain is due to fat accumulation, commonly distributed in the breasts, upper arms, back, and thighs. Anticipatory guidance regarding these predictable changes is important psychologically for many teenagers to have realistic expectations.
A large national study compared the age at menarche in the 1960s to the period from 1999 to 2002. Overall, an earlier age of pubertal onset of 4.9 months was documented. Some intriguing research is indicating such advancement may be partially due to excessive weight gain. Speculation regarding the possible role of cattle and poultry feed/hormone supplementation also exists. Different racial groups also demonstrate different times for the onset of puberty (African-American girls at 8.9 years of age vs. Caucasian girls at 10 years of age). Large studies of Hispanic and Asian girls are incomplete. Most recent research has isolated several genes (LIN28B and GPR54) that seem to have important regulatory roles in the age of menarche and onset of puberty, respectively.
Several physiologic and psychological processes are experienced by many teens during the pubertal and postpubertal years of young adulthood. Some of these situations may be unknown to both teen and parent (for example, risk for anemia in girls following menarche) and/or carry emotional ramifications (for example, acne). Anticipatory counseling and sympathetically addressing issues are an important part of the doctor-patient relationship. The pitfalls of puberty include anemia, male gynecomastia, acne, musculoskeletal injuries, gynecological issues, myopia, scoliosis, sexually transmitted diseases (STDs), and psychological concerns.
The Third National Health and Nutritional Examination Survey (NHANES III) documented that approximately 10% of menstruating girls between 12-15 years of age are iron deficient. In the same age range, less than 2% of boys were iron deficient. Causes are felt to include the effect of male sex hormones (for example, testosterone), monthly menstrual bleeding, and insufficient dietary intake of iron by females. Encouraging routine intake of lean red meat (vs. poultry, fish, and/or green leafy vegetables) and a daily multivitamin supplement (which may also augment calcium intake) should be encouraged if dietary sources are inadequate.
Approximately half of boys will experience either one-sided or bilateral breast tissue swelling during puberty. The average age of such a process is 13 years (Tanner III), and such a situation may last for six to 18 months. The size of breast tissue swelling is generally about 2 cm in diameter. While the underlying cause is generally benign and self-resolving, other causes should be considered if indicated. Some of these alternative causes of gynecomastia include drugs, thyroid diseases, and testicular diseases. The importance of reassurance that this can be a normal part of puberty to the anxious male teen cannot be underestimated.
Perhaps the most dreaded consequence for the pubertal teen is acne. This rite of passage is a combination of plugged sebaceous glands and local infection. Three areas are most commonly involved: the face, upper chest, and upper back. Acne tends to become most impressive at the Tanner III-Tanner IV maturation level. Extreme acne or significant acne prior to or at the early onset of puberty should raise concerns. Acne is generally felt to be an unintended consequence of a common testosterone/progesterone metabolic breakdown hormone (DHEA-S). Multiple therapeutic agents may be considered if acne is severe, and the adolescent with acne should discuss his/her situation with their doctor.
An asynchronous maturation of bone growth, bone strength and calcification (see above), muscle mass and strength, and tendon/ligament strength is an underlying problem that can commonly lead to a high rate of musculoskeletal injuries in adolescents. Likewise, the level and intensity of sports competition is another factor. The likelihood of risk-taking behaviors and a perceived sense of invincibility cannot be ignored. The current pattern of year-round single sport participation (vs. multiple sports and "breaks" during the year) is also felt to be associated with the growing increase in sports-related injuries and conditions in adolescents. The much higher than expected frequency of anterior cruciate ligament (ACL) damage in female basketball players is a reflection of such underlying physiology and social changes in sports participation.
A majority of females report that within one year of menarche they are having 10 or more periods per year. Studies have indicated that many (up to one-half) of these periods are not associated with ovulation. This information is sometimes used in an inappropriate manner by sexually active young teens believing that this provides a "natural" form of contraception. Counseling regarding the odds of such gambling should be presented to all young teens during their early menstrual life.
Because of asymmetric growth of the globe of the eye during puberty, many teens discover the need for corrective lenses.
Due to the accelerated growth of the skeleton during adolescence, it is important to screen for the development of or exaggeration of established scoliosis in both genders. Significant scoliosis is more common in females. The large majority of scoliotic curves "point" to the patient's right (when viewed from behind the patient). A curve directed to the left is more commonly a consequence of an underlying process and should warrant further diagnostic testing.
The highest incidence of STDs occurs in sexually active teens. Biological reasons for this epidemic include an earlier age of menarche coupled with the relative lack of maturation of the lining tissues of the cervix during the first one to two years following menarche. This immaturity makes infection with Chlamydia and human papillomavirus (HPV) more likely. Behavioral issues associated with the high rate of STDs in teens include an earlier age of first intercourse and a false perception of invincibility ("It won't happen to me").
The attainment of puberty has been observed to coincide with many profound psychological changes. It is important to realize that the refinement of abstract thought (for example, ability to intellectually explore various possible behaviors and anticipate realistic consequences) takes place in late puberty and extends into young adulthood (18-25 years old). The incidence of depression also rises during the teen years -- more frequently in females than males. Some studies have indicated that boys tend to develop a stronger self-image as puberty advances; females are thought to have a more self-critical body-image perception during early and mid puberty. Racial background studies indicate this self-depreciating phenomenon is more likely in Caucasian vs. African-American females. Girls who start puberty earlier than their peers appear to have a more stressful entry into this time of their life and are noted to have a higher likelihood of disruptive behaviors and possibly suicide attempts. Boys who are "late bloomers" are more likely to have issues with internalization and suppression of their feelings and may develop a stronger emotional reliance on others.
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Everyone develops at her own rate. A doctor should be consulted for girls who have not gotten their periods by age 15 or within a few years of breast growth. It is important to note that some girls don't get their periods until they're 16. Often the best predictor of when a girl will get her first period is when her mother got her first period.
