About Growth Disorders

Overview: Normal Growth and Puberty

1. Normal Growth Patterns

Human growth can be divided into four stages when viewed by growth rate.

1. Fetal period to 2 years of age (first growth spurt)

In general, at birth, a newborn's height is about 50 cm and weight is about 3.3 kg. By 1 year of age, height is about 75 cm and weight is about 10 kg, and around 2 years of age, height is about 87-88 cm.

2. Gradual growth from 2 years of age to puberty

This is a period in which growth is nearly constant at 4-6 cm per year, and by age 5, height becomes about 100 cm, roughly twice the height at birth.

3. Puberty to 15 or 16 years of age (second growth spurt)

Puberty differs by sex and even among individuals of the same sex, and it begins earlier in females than in males. In girls, puberty begins at an average age of 10 years, and in boys at an average age of 12 years. Girls grow a lot before menarche, increasing by an average of 6-10 cm per year. When menarche begins, growth slows for 2-3 years, and after menarche, height increases by only about 5-6 cm. The height at this time becomes the final adult height, though individual differences should be kept in mind. Once menarche begins, weight increases more than height. In other words, girls usually finish most of their height growth before menarche, and the average age of menarche in Korean girls is around 12 years old. In boys, puberty begins about 2 years later, and growth continues into the middle and later stages of puberty, with an annual increase of 8-12 cm. Because boys grow for 2 more years than girls, adult male height becomes greater than female height.

4. 15 or 16 years of age to maturity (a period in which growth rate decreases)

After puberty, the growth rate decreases sharply, and the body grows little by little until adult height is reached. In girls, by ages 14-16, and in boys, by ages 16-18, height usually grows by less than 2 cm per year and reaches adult height.

2. Factors Affecting Growth

Normal growth in children is determined by genetic and environmental factors. Genetic factors include things such as race, ethnicity, family line, age, and sex, and they are already determined from birth. Environmental factors include nutrition, socioeconomic factors, disease, season, and psychological factors, which can affect growth after birth.

In the past, the influence of heredity on height was thought to account for only 20-30%, and environmental factors were considered more important. However, many studies published to date have shown that hereditary influence is greater. Therefore, if a child is smaller than peers, it is necessary to check whether the child has been small since birth, whether family members are late growers, or whether the whole family is short. It is also a good idea to measure and record the child's height and weight every year and to have a general physical examination before entering elementary school.

3. Puberty

1. The onset of puberty and the pubertal growth spurt

Puberty is the period when the body and mind mature into adulthood, and it is the period when secondary sexual characteristics appear. With the development of the ovaries and testes, the reproductive organs develop so that pregnancy becomes possible. The most important features of puberty in females are breast development and the start of menstruation. In males, it begins with an increase in testicular size.

(1) Puberty in boys

The average onset of puberty in boys is 11.5 years old, meaning puberty begins around 6th grade of elementary school to 1st grade of middle school. During this time, the testes and penis enlarge, pubic hair appears, acne may develop, and after the voice changes, height increases rapidly relatively late. The pubertal growth spurt is the fastest growth period after infancy; during this time, boys grow about 25-30 cm over 2-3 years, and after facial hair and underarm hair begin to appear, growth slows and height growth stops 2-3 years later, around the 1st or 2nd year of high school.

(2) Puberty in girls

Girls begin puberty about 2 years earlier than boys, with breast development starting at an average age of around 10 years, followed by pubic hair and menarche. From the time the breasts begin to develop until menarche, height grows rapidly over about 2-3 years. During this period, girls grow an average of 15-20 cm. After menarche, growth slows, but height continues to increase for another 2-3 years, so it is generally normal for growth to stop after the 2nd or 3rd year of middle school. In girls, menarche begins at a bone age of about 12-13 years, and after menarche, they grow an additional 3-6 cm for about 3 years.

The difference in adult height between males and females is about 13 cm because puberty begins later in boys than in girls, boys are taller before the onset of the pubertal growth spurt, and boys grow more during the pubertal growth spurt.

2. Growth during puberty and hormone secretion

The reason height increases suddenly during puberty is due to various hormones. Sex hormones directly affect the growth cartilage and indirectly increase the secretion of growth hormone. Therefore, patients with a deficiency of sex hormones do not show the pubertal growth spurt. The secretion of growth hormone increases during puberty and stimulates the production of insulin-like growth factor-I (IGF-I), which regulates the pubertal growth spurt. In addition, a sufficient amount of thyroid hormone is necessary for cartilage growth. Therefore, patients with hypothyroidism do not experience the pubertal growth spurt.

So far, I have explained growth disorders.

In the next installment, we will look at the causes of growth disorders.

Source: National Health Information Portal, Korea Centers for Disease Control and Prevention