Current US Height And Growth Facts And Figures

I think it is without question that what people really want when they make a proclamation or wish that they “want to grow taller” is that they want to go through the process of growth spurts. There has been many cases where regular sized people who are living their lives suddenly get hit by this strange phenomenon and they find themselves far taller and bigger after just a season or year of dramatic body altering transformation.

When we are talking about growth spurts, we are not talking about the usual slow rate of body size increase which most young people and children experience. The average rate of height increase within USA

Let’s look at the scientific numbers behind the usual cause of a person’s growth and height , at least the US facts and figures available.

Girls

Most girls start their sexual development between the ages of 8 and 13, and have a growth spurt between the ages of 10 and 14.
– The rate of growth in height reaches its peak by about 2 years after puberty began (average age is 12 years).
– Menstruation begins, almost always after the peak growth rate in height has been reached (average age is 12.5 years).
– Once girls start to menstruate, they usually grow about 1 or 2 more inches, reaching their final adult height by about age 14 or 15 years (younger or older depending on when puberty began).

Boys

Most boys start developing sexually between the ages of 10 and 13, and continue to grow until they’re around 16.
– Boys tend to show the first physical changes of puberty between the ages of 10 and 16 years. They tend to grow most quickly between ages 12 and 15.
– The growth spurt of boys is, on average, about 2 years later than that of girls.
– By age 16, most boys have stopped growing, but their muscles will continue to develop.

(Note: Information taken from Kids Health)

From the Health Center at USC (University of Southern California) HERE 


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.

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


From KeepKidsHealthy.com

While there are many medical causes for being short and having poor growth, including growth hormone deficiency, hypothyroidism, Turner syndrome, inflammatory bowel disease, kidney problems, malnutrition, etc., most children who are short are normal. They may have genetic short stature or a constitutional growth delay.

Children normally grow at a rate of about 23-28 cm/year in early infancy (birth to 12 months) and this then decreases to about 7.5 – 13 cm/year in later infancy (1 – 3 years). Many children between the ages of 6 and 18 months move up or down on their growth percentiles, but by 24 months, most children follow their growth curve and stay on the same percentile or growth channel.

In early childhood (3 years to puberty) they will then continue to grow at a rate of about 4.5 to 7 cm/year, up until the time just before they begin puberty, when their growth will slow to about 4 cm/year. Growth then accelerates again as they hit their peak growth velocity in puberty, to about 8-9 cm/year for girls and 10.3 cm/year for boys. Growth then slows again in girls to about 7 cm/year after menarche (the first period) until they reach their adult height. Boys and girls usually continue to grow until they are 14-16 years old, but this depends on when they started puberty.

Among the influences on a child’s growth is his overall genetic potential for growth, which can be determined from his parents heights, his nutritional status, and the presence of any chronic medical problems.

Children with short stature are usually below the 3rd or 5th percentile on their growth chart for their height. But just as important as where they are on or below the growth chart is what their growth velocity or rate of growth has been each year.

It is also important to look at a child’s weight, in relation to his height. Since overweight or obese children are usually very tall because of an accelerated growth rate, if your child is short and overweight, then he should be evaluated for a medical condition causing his growth problems.

Among the tests that are commonly performed to evaluate the growth of a child with short stature include determining a bone age, which is the chronological age of your child’s bones. This is determined by taking an xray, usually of his left wrist and hand. If your child’s bone age is much less than his chronological or real age, then there is probably still room for his bones to grow after the age that you would normally expect him to already stop growing. Girls usually continue to grow until a bone age of about 14 years, and boys stop growing after a bone age of 16 years (with a peak growth rate at a bone age of 14 years).

Other tests can include blood tests to check for hypothyroidism (T4 and TSH), growth hormone levels (usually by checking IGF-1 and IGF BP3), complete blood counts (CBC to check for anemia), blood chemistries (which can include a SMA 20 to check for liver and liver disease), urinalysis, and sometimes a karyotype to look for chromosomal abnormalities (especially in girls who may have Turner syndrome).

If the above tests are normal, or if your Pediatrician didn’t think that testing was even necessary (which is often the case for many short children), then your child’s rate of growth can just be closely followed every 3-6 months, with a further evaluation being performed if he does not continue to have a normal rate of growth.

Since familial and genetic influences strongly determine how a child grows, most children with short parents will have short children. This is termed familial short stature. You can use our height calculator to figure out your child’s genetic potential for height based on his parents heights using our Height Calculator. While children with familial short stature may be at or near or just below the 3rd or 5th percentile on their growth chart for their height, their growth curve or channel will run parallel to the normal growth curves and they have a normal rate of growth. They also have a bone age that is close to their chronological age, showing that there is not any extra room or time to grow. Although growing normally, children with familial short stature will usually be short as adults, with a similar height to their parents.

Another normal condition that can cause short stature is aconstitutional delay in growth. These children, although short, have a normal growth velocity or rate of growth and will usually have a delay in starting puberty, and possibly a prolonged slowdown in growth that is usually present in children just before they begin puberty. They will usually also have a bone age that is much less than their chronological age, showing that there is room to grow and that they will continue growing even after other children of the same age have stopped growing. Because of the extra room and time to grow, children with constitutional delay usually have a normal adult height. Similarly, other family members usually also report a delay in starting puberty and a late adolescent growth spurt and have a normal final adult height. While children with a constitutional delay in growth will eventually begin puberty, go through the pubertal growth spurt and reach a normal final adult height, it can be distressing for many teens to be so much shorter and less developed than their peers. In this case, he may need referral to a Pediatric Endocrinologist for an evaluation and possible treatment with montly testosterone injections to hasten the start of puberty (although it will eventually start on its own without treatments).

Many parents are worried about growth hormone deficiency in their short children. Growth hormone is required for normal growth, and children with growth hormone deficiency are short, often look younger than their chronological age, and they can be chubby with their weight higher than their height. While they will usually have a delay in their bone age, like children with a constitutional delay, children with growth hormone deficiency will have a slow rate of growth and they will have a growth curve that falls away from the the normal growth curves (unlike other normal causes of short stature which have a normal rate of growth and a growth curve that runs parallel to the growth chart). Testing that can be done if your Pediatrician suspects your child has growth hormone deficiency include checking the levels of IGF-1 and IGF BP3, which will be low. A growth hormone stimulation test may also be done by an endocrinologist.

Treatments for growth hormone deficiency include growth hormone replacement. Other conditions for which growth hormone is currently being successfully used include Turner syndrome, chronic renal failure and Prader-Willi syndrome.

Growth hormone defiency may be congenital (a child is born with it), or it may be acquired later in life from head injury or a brain tumor or mass.

Recently, the indications for which kids can be treated with growth hormone has been expanded. Growth hormone can now be used for the long-term treatment of children with idiopathic (of unknown origin) short stature, also called non-growth hormone deficient short stature, who are more than 2.25 SD below the mean for age and sex, or the shortest 1.2% of children. For example, according to the FDA, for 10-year old boys and girls, this would correspond to heights of less than 4′ 1″ inch. This would further correspond to heights of less than 5′ 3″ and 4′ 11″ in adult men and women, respectively.

Some new studies and reports have recently shown that another group of these short kids, those who were born Small for Gestational Age (SGA), may also benefit from treatment with human growth hormone. The International Small for Gestational Advisory Board has recommended that if ‘a short child who was born SGA has not caught up by age 2 to 3 years of age and whose catch-up growth has stopped should be referred to a pediatrician who has expertise in endocrinology.’


From LiveStrong Article HERE

According to Chao-Qiang Li, a molecular biologist at the U.S. Department of Agriculture Human Nutrition Center, 60 to 80 percent of height is genetic. Another 20 to 40 percent of height is attributed to environmental factors. A third factor is age. As we age, we tend to lose a few inches. Regardless of how tall you may grow to be, science hasn’t made any definite pronouncement as to how tall human beings are capable of growing. 
Genetic FactorsThere are a wide variety of factors that contribute to how tall a man or women becomes. Research has shown that genetics play a large role in height. Research indicates there’s a strong correlation between the height of a mother and her son, as well as the height of a father and his daughter. Scientists have isolated a gene known as HMGA2. This gene is believed to contribute to height variations.

Environmental Factors

Diet, exercise and living conditions play a large role in determining the height of men and women. Those living in areas that are stricken with poverty, war or natural disasters are more likely to have a lower average height than those living in areas where the population is healthier. Ethnicity also plays a role in height. For example, males in China are — on average — 1 inch shorter than males who live in the United States.Sex Differences

More often than not, men are taller than women. While women have a tendency to grow and reach their full height at a young age, men frequently surpass women in height by the time they reach their early 20s. Sex chromosomal differences account for the differences in height. The XY chromosome — male — and the XX chromosome — female — play a large role in the height differences between males and females.Average Heights

In a 2004 study conducted by the Centers for Disease Control and Prevention, the average height of men between the ages of 20 and 74 is 5 feet 9 inches tall. Women are an average of 5 feet 4 inches tall.Me: The main point of this post was for the reader to be more informed on the current knowledge and facts about height and the average rate of height growth that is exhibited in the US teenage and adolescent population. 

 

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