Definition/Significance
Purpose of this Program
The purpose of this instructional unit is to describe the physical events that occur as a child grows through adolescence. In this program, we are going to describe features associated with sexual maturation and the developmental events that relate to cranial and facial growth.
Then, we will discuss the importance of normal variations in the pattern, timing, and rates of growth. Finally, we will address why it is important to be able to assess individual levels of maturity.
In addition to viewing the module, read Contemporary Orthodonticspages 92-96 (5th ed), 107-111 (4th ed). Be sure you are able to:
- describe the endocrinologic changes that lead to the onset of puberty
- describe the difference of timing of puberty in boys and girls
- describe the stages of sexual maturation in boys and girls
- discuss the impact of puberty on the growth of the major types of tissues (neural, general body, lymphoid, sexual)
- describe the effect of earlier vs. later maturation on ultimate body size
- discuss the relationship of jaw growth to the efficiency of orthodontic treatment during the adolescent growth spurt.
What is Adolescence?
Adolescence is a sexual phenomenon.
It is defined as the stage of growth and development when sexual maturity is attained, and this stage of sexual development is referred to as puberty.
It can be defined more specifically as the transitional period between the juvenile stage and adulthood, during which:
- Secondary sex characteristics appear
- Fertility is attained
- The adolescent growth spurt takes place
- Profound psychological changes take place
All these developments are associated with the maturation of the sex organs and the concomitant surge in secretion of sex hormones.
Growth Events: Clinical Significance
Changes at adolescence significantly affect the face and dentition. Three major growth events affecting the dentition take place along with the onset of adolescence. These are:
- Exchange of the dentition from mixed to permanent
- An acceleration in the overall rate of facial growth
- Differential growth of the jaws, i.e. more growth in some areas than others
Why do you need to understand these events? Because any dentist must understand the relationship between growth events that occur during adolescence so that he or she can:
- recognize and assess stages of development in patients
- help solve developing problems of dentofacial disharmony
Growth Spurt Characteristics
Adolescent Growth Spurt
Examine Scammon’s growth curves from the point of view of sexual maturation and the adolescent growth spurt. Note that upon the onset of puberty:
- There is an almost explosively rapid growth and development of the sex organs
- Lymphoid tissue decreases in size—tonsils, adenoids and the like shrink
- Neural growth is unaffected by sexual maturation—it has been largely completed by then
- General body growth shows changes in response to sexual growth
Hormones: the Basis of Adolescence
Since puberty is a sexual phenomenon, and sex hormones are the mediators of the changes we are most interested in, we will start with an overview of the hormonal events. The genital growth curve is also representative of the change in blood level of the sex hormones. Significant amounts of the male and female sex hormones first appear at puberty. Hormones are released into the blood stream in a process called endocrine secretion—thus we can say that we are talking about the endocrinology of adolescence.
Remember that we want you to understand the big picture. Concentrate on that, not the fine details.
Hormones of the Growth Spurt
Three types of hormones are sequentially involved in the growth spurt:
The hypothalamic releasing factors are the hormones that initiate the growth spurt. They are produced in the brain region called the hypothalamus. Their target is the anterior pituitary gland.
The pituitary gonadotrophins are the second type of hormones. They are produced by the pituitary gland, in response to the hypothalamic releasing factors. Their target is the testis in the male and the ovary in the female, with some effect on the adrenal cortex in both sexes.
The sex hormones themselves are the third type of hormones produced by the ovary, testis and adrenal cortex. They have varied effects on tissues throughout the body. Chemically, the sex hormones are all steroids—but not all steroids are sex hormones, only a few with special properties.
Endocrinology-Step 1
The first events of puberty occur in the brain, and the stimulus for their unfolding remains unknown. For whatever reason, perhaps in response to some kind of internal clock, perhaps in response to a pattern of outside stimuli which we have not recognized, cells in the hypothalamus begin to secrete substances which are called releasing factors.
Both the cells and their method of action are somewhat unusual. These are neuro-endocrine cells. They look like typical neurons but they secrete materials in the cell body that are carried by cytoplasmic transport down the axon toward a richly vascular area at the base of the hypothalamus near the pituitary gland.
The Pituitary Portal System
The substances secreted by the nerve cells pass into capillaries in this vascular region, and are carried by blood flow the short distance to the pituitary gland. It is unusual in the body for capillaries to pass from one region to another, but here the special arrangement of the vessels seems made for the transport of materials from the hypothalamus to the pituitary. Accordingly, the special network of blood vessels is called the pituitary portal system.
The first step in the endocrinology of adolescence would be the arrival of our unknown stimuli in the hypothalmus, which cause the neuro-endocrine cells in that region to begin secreting their releasing factors.
Endocrinology-Step 2
The second step occurs at the pituitary gland, where the releasing factors in turn stimulate pituitary cells to produce hormones called pituitary gonadotrophins. There are at least two of these hormones, with perhaps others involved. Their function is to stimulate endocrine cells in the developing sex organs to produce sex hormones. Their target is the testis in the male and the ovary in the female, with some effect on the adrenal cortex in both sexes.
Male Endocrinology-Step 3
In the male, cells in the testis produce the male sex hormones, including testosterone, but there are also other cell types in the testis (especially the Leydig cells) that produce female sex hormones. Different gonadotrophins stimulates these cell types.
As you already know, every individual has a mixture of male and female sex hormones. There are a number of hormones, testosterone the primary one, that, in addition to their other functions, promote growth leading to a more masculine body form. These collectively are termed androgens. Conversely, there are a number of hormones, estrogen the primary one, that promote growth leading to a more feminine body form. These collectively are termed estrogens.
Female Endocrinology-Step 3
In the female, the pituitary gonadotrophins stimulate secretion of estrogen by the ovaries, and later progesterone by the same organ. In the female, male sex hormones are produced in the adrenal cortex, and possibly some female hormones are produced in the male adrenal cortex.
Endocrinology-Step 3
Under the stimulus of the pituitary gonadotrophins, sex hormones from the testis, ovary, and adrenal cortex are released into the blood stream in quantities sufficient to cause accelerated growth of the genitals and the development of secondary sex characteristics.
The increasing level of the sex steroids in the blood also causes other physiologic changes, including the acceleration in general body growth and shrinkage of lymphoid tissues.
Different levels of androgens and estrogens in males and females cause differences in the adolescent growth spurt.
Summary of Endocrinology
Perhaps you are wondering about the reason for such a complicated control system. The purpose of having a three-stage hormonal process is to amplify the small signal that begins in the brain.
In the hypothalamus, only a few nerve cells are involved, and they produce a few molecules of releasing factor—a very weak signal.
Those few molecules serve to stimulate a number of cells in the pituitary gland, and these cells in turn release a quantity of gonadotrophic hormones which is considerably larger than the original amount of releasing factor.
This amount of gondotrophic hormone in turn serves to stimulate a larger number of cells in the gonads, so that the amount of sex hormones ultimately produced is many thousands of times the amount of releasing factor back at the hypothalamus. Thus, a small signal from the brain has a large and continuing effect on the body.
Male/Female Differences
Adolescent Growth
Puberty and the adolescent growth spurt tend to occur considerably earlier in girls than in boys. From cross-sectional incremental growth curves for boys and girls, you can see that on the average, puberty occurs one and a half to two years earlier in girls than in boys.
Why this occurs is not known—it is just one of the biological facts of life. Perhaps you remember those embarrassing junior high school days when most of the girls were very eager to attend a dance but had great difficulty in finding a boy who was willing to go. Two years later, all that had changed remarkably as sex hormone levels in the boys caught up.
Of course you also realize that there is a great deal of individual variation in the timing of adolescence in both boys and girls. The early maturing boys will reach puberty well ahead of the slow maturing girls, and chronological age has very little to do with where an individual stands developmentally.
Physiologic Maturation
It will be important to you to be able to judge the degree of physiologic maturation which your patients have achieved, so that you will have some ideas about their growth status. If you had growth records on every patient, that would be easy, but of course you won’t have that. How could you do it?
Obviously, you need to be able to assess some markers of physiologic maturation. The degree of development of the secondary sexual characteristics provides such a marker. While it is true you will not have the opportunity to evaluate all of these characteristics, many will be visible under normal dental office conditions. Fortunately, there is a good correlation between development of secondary sexual characteristics and the individual’s position on the growth curve.
Stages in Female Sexual Development
Let us begin by looking at the relationship between height gain in girls and secondary sexual characteristics. For convenience, we can identify three stages in development of the secondary sexual characteristics, labeled I, II and III on this graph. Stage I is at the beginning of the growth spurt; stage II is at the peak; and stage III is on the downslope toward the end of the growth spurt.
Female Stage I
The first stage in secondary sexual characteristics for girls occurs very near the beginning of the growth spurt. The initial sign of sexual maturation is the appearance of breast buds and early stages of pubic hair.
| Image 1, Height gain per year for girls: Stage 1 includes the appearance of breast buds and pubic hair. |  Image 2 |
Female Stage I (cont.)
The breast and papilla elevate to a small mound and the diameter of the areola increases. Pubic hair is slightly pigmented and is sparsely distributed along the labia. The illustrations shown here may be slightly more advanced already than early Stage I.
 Image 1 |  Image 2 |
Female Stage 2
The peak velocity for growth in girls occurs about one year after stage one, and coincides with stage two of development of secondary sex characteristics. At this time, there is noticeable breast development. Pubic hair is darker and more widespread. Hair appears in the armpits (axillary hair).
 Image 1, Height gain per year for girls: Stage 2 includes noticeable breast development as well as pubic and axillary hair. |  Image 2 |
Female Stage 2 (cont.)
Breast development shows growth and elevation of both breast and areola with contours being smooth. Pubic hair is darker, coarser, and curled.
 Image 1 |  Image 2 |
Female Stage 3
The third stage in girls occurs about one to one and one-half years after stage two. By this time, the growth spurt is all but complete, and this stage is marked by the onset of menstruation. By now, there is noticeable broadening of the hips with a more adult fat distribution, and development (though not necessarily growth) of the breasts is complete.
 Image 1, Height gain per year for girls: Stage 3 is marked by the beginning of menstruation. |  Image 2 |
Female Stage 3 (cont.)
The breast shows more adult contours with the areola and papilla forming a secondary mound.
Pubic hair has a more adult distribution with some spread to medial surfaces of the thighs.
 Image 1 |  Image 2 |
Male Sexual Characteristics
The stages of sexual development in boys are more difficult to specifically define than in girls. The process of puberty begins later in boys and extends over a longer period of time.
Note in the graph that for boys, the process extends over about a five year period, while in girls puberty extended over a 3 ½ year period. We will define four stages in development of secondary sexual characteristics in boys, again indicating the position on height curve which roughly corresponds with the sexual characteristic stage.
Stage I is at the beginning of puberty, with a slight increase in the growth rate; stage II is at the beginning of the growth spurt; stage III is at the peak; and stage IV is toward the end of the growth spurt.
Male Stage 1
The first stage of sexual development for males is the “fat spurt”, as adipose tissue increases throughout the body. The initial sign of male puberty, interestingly, is the development of a more feminine body form. It appears that the estrogen-producing cells in the testis are stimulated by the pituitary gonadotrophins before the androgen-producing cells.
At this time also, the scrotum begins to increase in size and may show some increase or change in pigmentation, while the penis remains juvenile.
Male Stage 1 (cont.)
During this stage, boys may appear to be obese and somewhat awkward physically. At this time also, the scrotum begins to increase in size and may show some increase or change in pigmentation, while the penis remains juvenile (image 2).
Male Stage 2
At stage two, about one year after stage one, the spurt in height is just beginning (image 2). At this stage, pubic hair appears above the penis, and there is growth of the penis, increasing size of the testes, and increasing size and pigmentation of the scrotum (image 3). There also is a redistribution and relative decrease in subcutaneous fat, so that the chubby appearance decreases and body form becomes more like that of an adult male.
 Image 1 |  Image 2, Height gain per year for boys: Stage two sees the end of the fat spurt and a sharper increase in height gain. |
 Image 3 |
Male Stage 2 (cont.)
As stage 2 develops, “peach fuzz” (fine unpigmented hair) appears on the upper lip, and as stage 3 and the height of the growth spurt approaches, pigmented hair starts to appear on the upper lip.
At age 10 yrs 2 months (image 1), this boy shows none of the characteristics of early adolescence. The fat spurt is more obvious in some individuals than others, but he has not reached that stage, and has no sign of any hair on his upper lip.
At age 11 yrs 4 months (image 2), his parents report that he has recently started to grow. It’s hard to see in the photo, but he has the beginnings of unpigmented hair on his upper lip. This is another sign that he’s entering his growth spurt. If you’re trying to take advantage of growth during orthodontic treatment, this would be a good time to start (in fact, if you look closely, you can see that he’s just had braces put on his teeth). There’s nothing to be gained by starting earlier.
 Image 1, Boy aged 10 years, 2 months: No evidence of early adolescence present. |  Image 2, The same boy fourteen months later: Hair on the upper lip is one good indicator that the growth spurt has begun. |
Male Stage 3
The third stage occurs 8-12 months following stage two and coincides with the peak velocity in gain in height. At this time, axillary hair appears. For most boys the first facial hair is “peach fuzz” (fine unpigmented hair) on the upper lip (as shown in the previous screen), which tends to appear before the peak of the growth spurt.
The appearance of pigmented facial hair on the upper lip (no hair on the chin yet) is an indicator that a boy is about at the peak of growth. A spurt of muscle growth also occurs, along with continued decrease in subcutaneous fat and an obviously harder and more angular body contour.
In this boy (image 3) at age 14-8 (when his orthodontic treatment ended), the pigmented hair on the upper lip is apparent. It first appeared several months previously.
 Image 1: Stage 3 occurs 8-12 months following stage 2. The greatest increase in height takes place during this phase. |  Image 2 |
 Image 3: Dark pigmented hair on the upper lip is a good indicator of stage 3 in boys. |
Male Stage 3 (cont.)
In stage 3, pubic hair distribution appears more adult but no spread to the medial of the thighs has occurred. Penis and scrotum are near adult size.
Male Stage 4
Stage four for boys is difficult to pinpoint. This occurs anywhere from 15 to 24 months after stage 3. At this time, the spurt in growth in height ends. By then there is the beginning of facial hair on the chin as well as the upper lip, further increase in muscle mass and redistribution of fat toward the body image of an adult male, and a spurt in muscular strength.
 Image 1, Height gain per year in boys: Stage 4 occurs quite some time after stage 3 and is characterized by facial hair on the chin and an increase in muscle strength. |  Image 2 |
Male Stage 4 (cont.)
Pubic hair distribution is nearly adult with some spread to medial thigh and some spread beginning in a sagittal direction toward the umbilicus. The scrotum and penis have reached full adult size.
Differential Growth
Correlation
If information about physical growth status is to be applied to dentofacial development, it is important to know how growth in the face and jaws correlates with growth elsewhere. Our information so far has correlated sexual development with growth in height.
Does growth in height correlate with jaw growth? Fortunately, it does. The acceleration in height occurs at the same time as an acceleration in growth at the mandibular condyle and a slight acceleration at the sutures of the maxilla. So careful observation of the stage of secondary sexual characteristics would give a dentist insight into the stage of growth of the jaws as well as skeletal growth more generally.
Correlation: Differential Growth
Note that these curves for increments of growth show that during the adolescent growth spurt, there is more growth at the condyles (mandibular growth) than at the sutures (maxillary growth). You have seen the same thing previously on distance curves for maxilla and mandible. The maturing face becomes less convex as the mandible becomes more prominent because of differential jaw growth.
Treatment Timing: Headgear
Orthodontic treatment for the most common growth problem in children of European descent, protruding maxillary incisors because of deficient mandibular growth (i.e., skeletal Class II in the terminology with which you will soon become very familiar), is timed to coincide with the period of rapid growth at adolescence when possible because it is more effective at this time.
Suppose the lower jaw is somewhat behind the upper jaw—a common problem—but is growing forward relative to the upper jaw as it normally does during the adolescent growth spurt. We can apply force to the sutures of the maxilla with a “headgear” appliance (figures 1 and 2). Sutures react, and the external force can alter the direction of maxillary growth, holding the maxilla while the mandible grows forward.
Appliances like this can produce a considerable change in jaw relationship, but only if differential growth is occurring. Headgear to the maxilla only works if the mandible is growing. That’s why it’s so important to know where things are on the development scale in order to do orthodontic treatment at the most advantageous time.
 Image 1, High-pull headgear: The cap on the top of the head directs force up and back against the growing maxilla. |  Image 2, Cervical-pull headgear: The neck strap directs force down and back against the growing maxilla. |
Treatment Timing: Functional Appliances
It isn’t necessary to use extra-oral appliance like headgear to take advantage of differential jaw growth. This device, one of a group of similar intra-oral devices collectively called functional appliances, is a bionator. By holding the mandible forward, it can influence the growth of both the mandible and maxilla, and it also guides the posterior teeth as they erupt.
This takes advantage of our final correlation: the transition from the mixed to the permanent dentition also tends to occur along with the other growth changes at adolescence. With all those changes going on, it’s a great time to be correcting any problems in the way teeth and jaws are arranged.
 Image 1, A Bionator appliance: By functioning, or biting together, with the appliance in place, the saggital relationship of the teeth and jaws is improved – a functional appliance, if jaw growth is occurring. |  Image 2, A Bionator appliance: By functioning, or biting together, with the appliance in place, the saggital relationship of the teeth and jaws is improved – a functional appliance, if jaw growth is occurring. |
Normal Variations
Maturation
So far, we have discussed the “why” of adolescence, in terms of its endocrinology, and the “what” in terms of physical growth and its relation to the appearance of primary and secondary sexual characteristics.
Can you describe the pattern of changes and discuss the timing of adolescence? By now, you should be able to draw and label the incremental growth curves from memory.
Now let’s talk about variability.
Maturation Variability
These 13-year-old boys, who participated in a growth study, are in the same class at school and only a few months apart in age. It’s obvious that chronological age is far from reflecting their growth status. The bigger boy is much more mature sexually. A close look at his face that showed you hair on his upper lip but not on his chin could tell you a lot about where he is on the growth curve. The timing of onset of puberty makes a big difference in size in the seventh grade.
What do you think the effect of early puberty is on final height as an adult? Would you be taller if you matured early? Shorter? The same size?
Maturation: Effects on Bone Growth
You’ll remember that growth in height depends on endochondal growth at the epiphyseal plates of long bones. The answer to the effect of maturation timing on adult height derives from the fact that the impact of the sex hormone on endochrondral bone growth is two-fold.
First, the sex hormones stimulate the cartilage to grow faster, and this produces the adolescent spurt in height. Secondly, the sex hormones also cause more rapid maturation or transformation of cartilage into bone, and the speed-up in maturation is even greater than the acceleration in growth.
Thus, during the adolesent growth spurt, the cartilage is used up faster than it is replaced. Toward the end of sexual maturation, the last of the cartilage is transformed into bone and the epiphyseal plates close. At that point, of course, growth potential is lost, and growth stops.
Now, knowing that, what’s the answer? Would you be taller if you mature early? Shorter? The same size?
Maturation: Timing and Ultimate Height
All other things being equal, the earlier you mature sexually, the shorter you will be as an adult. Perhaps you remember seeing that happen among your contemporaries. Remember the boy who was the biggest guy in the 6th grade? But he is nearly the same size as an adult as he was then, and now is relatively short, while one of the runts then is one of the biggest men now. An early-maturing girl who was the tallest in her middle school class will watch many others who hit their growth spurt later grow taller.
This phenomenon is responsible for much of the difference in adult size between men and women. Girls mature earlier on the average, and finish their growth much sooner. Boys aren’t bigger than girls until they grow for a longer time at adolescence. The difference arises because growth continues slowly prior to the growth spurt, and so for those who mature late, when growth spurt occurs it takes off from a higher plateau.
Timing of Puberty
Now let’s tie this relationship of timing of puberty and variation in final height together, to be sure you understand.
Look again at the growth velocity curves for girls who mature at various times. The early maturing girls tend to have a more intense but shorter growth spurt, and are likely to be all through growing by age 13 or so. They’d better have their orthodontic treatment early, too. The late maturing girls have a later and less intense growth spurt—but they are likely to be taller adults than the early maturers. The reason is that they grow at the pre-pubertal plateau level for a longer time, before the growth spurt and growth fade-out.
Timing of Puberty: Other Factors
Timing of puberty is a major contributor to variability, but this timing in turn can be related to other factors. There is a genetic influence on timing of puberty—of course your inheritance has strong influences on your growth potential. Somatotype, or body-build characteristics, affects timing of the growth spurt. A boy classified as an ectomorph—a slender one, like all 3 of these boys—will have a later growth spurt than his mesomorph, muscular friends—and after being shorter for years, he may end up taller. Seasonal and climatic variations have an interesting impact. Children mature faster in warmer climates, slower in colder ones, and growth in height is faster in the spring than fall.
Assessment of Maturity
By now you should be thoroughly convinced that developmental age is important. The stage of sexual development correlates strongly with physical development, so assessment of sexual maturity by observing the secondary sexual characteristics is important when you are dealing with adolescents.
Don’t forget that there are other ways of obtaining information about physiological maturity. Sequential height-weight charts and bone development as seen on radiographs are two that are important. You already know a lot about growth curves on height-weight charts and will be learning more about how to judge skeletal maturation from radiographs.
Summary
The adolescent period of life is characterized by attainment of sexual maturation. This is mediated by sex hormones and controlled through the hypothalamic area of the brain and the pituitary gland.
The adolescent growth spurt is characterized by sexual differences in timing, rate, and duration. Girls mature earlier—which is one important reason why they are smaller adults.
Assessment of physiological maturity is necessary in treatment planning, especially when orthodontic treatment is to take advantage of differential jaw growth.
Now that you have completed this module, be sure you have carefully read pages**92-96 (5th ed), 107-111 (4th ed) in *Contemporary Orthocontics.*Then take the self-test in the next section to be sure you understand what you have learned.
Self-Test
Question 1
The earlier you mature sexually, the _______ you will be as an adult.
- shorter ✓
- taller
- heavier
- lighter
Correct
That’s right. Early sexual maturation means earlier closure of the epiphyses of the long bones, so the earlier you mature, the shorter you’ll be, and vice versa.
Incorrect
That’s wrong. Early sexual maturation means closure of the epiphyses of the long bones, so the earlier you mature, the shorter you’ll be, and vice versa. But weight is affected only secondary if at all.
Question 2
Orthodontic growth modification during adolescence is aimed at:
- accelerating mandibular growth
- retarding maxillary growth
- retarding mandibular growth
- accelerating maxillary growth
- producing differential growth between maxilla and mandible ✓
Correct
That’s right. In order to correct jaw discrepancies, differential growth is needed. That might involve accelerlating or retarding the growth of either jaw.
Incorrect
No, that’s wrong. In order to correct jaw discrepancies, differential growth is needed. That might involve stimulating or retarding either jaw.
Question 3
The first step in the endocrinology of adolescence is:
- increased secretion of hypothalamic releasing factors ✓
- increased secretion of pituitary gonadotrophins
- increased secretion of estrogen
- increased secretion of testosterone
Correct
That’s right. Increased secretion of hypothalamic releasing factors is the first step in the endocrinologic cascade that leads to adolescence.
Incorrect
No, that’s wrong. Increased secretion of hypothalamic releasing factors is the first step in the endocrinologic cascade that leads to adolescence. Their secretion leads to increased secretion of pituitary gonadotrophins, which in turn stimulate release of estrogen, testosterone and the other sex hormones.
Question 4
The biologic purpose of the endocrinologic sequence is to:
- amplify the initial hypothalamic signal ✓
- modulate the initial hypothalamic signal
- compensate for the initial hypothalamic signal
- make the control circuitry redundant for greater safety in use
Correct
That’s right. The cascade serves as an amplifier, allowing the very small signal produced by only a few cells in the hypothalamus to control a large system.
Incorrect
That’s wrong. The cascade serves as an amplifier, allowing the very small signal produced by only a few cells in the hypothalamus to control a large system.
Question 5
Maximum growth velocity for mandible in boys occurs at which stage?
- stage I
- stage II
- stage III ✓
- stage IV
- unpredictable
Correct
That’s right. The adolescent growth spurt for the mandible coincides with the spurt in height, so it occurs at stage III just as the height spurt does.
Incorrect
That’s wrong. The adolescent growth spurt for the mandible coincides with the spurt in height, so it occurs at stage III just as the height spurt does.
Question 6
At which stage of sexual development in girls does pubic hair first appear?
- stage I ✓
- stage II
- stage III
- stage IV
- indeterminate, pigmentation may be delayed
Correct
That’s right. Pubic hair begins to form at the first stage of sexual development in girls, at the same time breast buds are noticed.
Incorrect
That’s wrong. Pubic hair begins to form at the first stage of sexual development in girls, at the same time breast buds are noticed.
Question 7
The “fat spurt” early in puberty in boys leads temporarily to a more feminine fat distribution pattern because (B) cells in the testis that produce estrogens are stimulated at this early stage before those that produce androgens.
- A true, B true, A and B related ✓
- A true, B true, A and B not related
- A true, B false
- A false, B true
- A and B false
Correct
That’s right, the statements are true and related. Estrogen release by cells in the testis (and adrenal cortex) leads to the fat spurt and the temporary feminine fat distribution.
Incorrect
That’s wrong, the statements are true and related. Estrogen release by cells in the testis (and adrenal cortex) leads to the fat spurt and the temporary feminine fat distribution.
Question 8
Which of the following is not a major player in the endocrinology of adolescence?
- hypothalamic releasing factors
- pituitary gonadotrophins
- male and female sex hormones
- adrenocorticotrophins ✓
Correct
That is correct. Adrenocorticotrophins are important before, during and after puberty, but they are not major players in the endocrinologic cascade that leads to adolescence.
Incorrect
That’s wrong. Adrenocorticotrophins are important before, during and after puberty, but they are not major players in the endocrinologic cascade that leads to adolescence.
Question 9
What of the following is not true concerning effects on adolescent growth?
- slender body (ectomorphic), later growth spurt
- heavy body (endomorphic), earlier growth spurt
- colder climate, earlier growth spurt ✓
- spring-summer, faster growth rate
- all are true
Correct
That’s right. All other things being equal, the adolescent growth spurt comes earlier in children who live in a warmer climate, not a colder one.
Incorrect
That’s wrong. All other things being equal, the adolescent growth spurt comes earlier in children who live in a warmer climate, not a colder one.
Question 10
In girls, which of the following is not an indicator of peak growth velocity?
- noticeable breast development
- axillary hair
- pigmented, curled pubic hair
- menstruation ✓
Correct
Noticeable breast development, axillary hair and curled pubic hair are all seen at stage II of adolescence, when growth velocity peaks. Menstruation doesn’t occur until growth velocity is declining.
Incorrect
That’s wrong. Noticeable breast development, axillary hair and curled pubic hair are all seen at stage II of adolescence, when growth velocity peaks. Menstruation doesn’t occur until growth velocity is declining.
Question 11
Which of the following indicates that a boy is beyond the peak of the adolescent growth spurt?
- fine “peach fuzz” on upper lip
- pigmented hair on upper lip
- hair on upper lip and chin ✓
- recent rapid growth in height
Correct
That’s right. The appearance of hair on the upper lip and chin is a good indicator that a boy is well beyond the peak of the adolescent growth spurt. He’s approaching if not in stage 4. Peach fuzz and pigmented hair on the upper lip are indicators of early and late stage 3, respectively. Recent rapid growth in height tells you he’s in the growth spurt but not where.
Incorrect
No, that’s wrong. The appearance of hair on the upper lip and chin is a good indicator that a boy is well beyond the peak of the adolescent growth spurt. He’s approaching if not in stage 4. Peach fuzz and pigmented hair on the upper lip are indicators of early and late stage 3, respectively. Recent rapid growth in height tells you he’s in the growth spurt but not where.
Question 12
(A) Early maturing boys reach puberty before late maturing girls because (B) the individual variation in when puberty starts is greater than the average differences between the sexes.
- A true, B true, A and B related ✓
- A true, B true, A and B not related
- A true, B false
- A false, B true
- A and B false
Correct
That’s right. Both statements are true and related. On the average girls reach puberty two years ahead of boys, but there’s at least a five year spread in the normal distribution for both sexes, so the early maturing boys easily can reach puberty before the late maturing girls.
Incorrect
That’s wrong. Both statements are true and related. On the average girls reach puberty two years ahead of boys, but there’s at least a five year spread in the normal distribution for both sexes, so the early maturing boys easily can reach puberty before the late maturing girls.