What affects growth?

Many factors influence growth

Growth varies with age. Many factors influence how much and how rapidly a child grows, and how tall he or she will be as an adult. Some of these factors can be controlled and others cannot.

Heredity

Heredity (the genes we inherit from our parents – our genetic potential) is one of the most important factors influencing a child's growth. Height varies among different ethnic groups, among different families within the same ethnic group, and even among members of the same family.

There is a relationship between the height of a child and the height of the child's parents. In general, if a child has a tall parent, he or she is likely to be taller than average as an adult. If one parent is shorter than average, the child may be shorter than average as an adult. The genetic influence on height is usually well established by the time a child is two years old.

The expected approximate adult height of a child can be estimated based on the height of the parents. By averaging the mother's height and the father's height (adjusted for the sex of the child), one can come up with a "target height" (also known as midparental height) for the child – the average height he or she would be expected to reach as an adult.

Target height for a girl

1. Convert the height of each parent into inches (for example, 5 feet, 10 inches = 70 inches).
2. Subtract 5 inches from the father's height – this is the father's "adjusted height."
3. Add the father's adjusted height to the mother's actual height.
4. Divide the total number of inches by 2.

The result represents the daughter's target height.

Example

1. Father's height is 70 inches and mother's height is 63 inches.
2. 70 inches - 5 inches = 65 inches (father's adjusted height).
3. 65 inches + 63 inches = 128 inches.
4. 128 inches divided by 2 = 64 inches.

The target height for this couple's daughter is 64 inches, or 5 feet, 4 inches.

Target height for a boy

1. Convert the height of each parent into inches (for example, 5 feet, 3 inches = 63 inches).
2. Add 5 inches to the mother's height – this is the mother's "adjusted height."
3. Add the mother's adjusted height to the father's actual height.
4. Divide the total number of inches by 2.

The result represents the son's target height.

Example

1. Father's height is 70 inches and mother's height is 63 inches.
2. 63 inches + 5 inches = 68 inches (mother's adjusted height).
3. 68 inches + 70 inches = 138 inches.
4. 138 inches divided by 2 = 69 inches.

The target height for this couple's son is 69 inches, or 5 feet, 9 inches.

This formula is helpful in estimating your child's adult target height. But it is also important to realize that it is possible for a normal individual's height to vary by up to 4 inches either above or below the target height once growth is complete.

Nutrition

A child's growth, both in height and weight, is also influenced by diet. A well-balanced, age-appropriate diet that includes carbohydrates, protein, fats, vitamins and minerals can have a positive affect on how well a child grows. Children who receive an inadequate amount of calories or nutrients may grow poorly; improving the diet of these children may improve growth.

However, there really is no "average" diet that is best for all children. A child's specific dietary requirements vary with age, physical activity level, and other factors. If you have questions about your child's diet, discuss them with your child's doctor.

Hormones

Hormones are the chemical messengers of the body. They are released from glands and circulate in the blood, affecting everything from growth and metabolism to blood pressure and mood. Almost all hormones affect growth to some extent, but some have particularly important roles in your child's growth.

Growth hormone is essential for growth. It is made by the pituitary gland (located at the base of the brain), then released into the bloodstream, where it travels to the body's tissues. Here it stimulates production of another hormone important for growth, known as insulin-like growth factor I, or IGF-I. Growth hormone works to stimulate growth in large part due to its effect in producing IGF-I.

Thyroxine (thyroid hormone) is produced in the thyroid gland, located at the base of the neck. It plays an important role in brain development and growth during childhood, and affects metabolism at all ages. Babies who are deficient in this hormone must be treated with thyroid hormone replacement from the newborn period to ensure normal growth and brain development.

Androgens are male-type sex hormones. "Weak" androgens are produced by the small triangular adrenal glands located above the kidneys, and "strong" androgens are made by the testes (male sex glands) in boys. In girls, androgens are also produced in smaller amounts by the adrenal glands and ovaries (female sex glands). Androgens trigger the development of hair in the armpits and genital regions of both boys and girls at puberty. Testosterone, made by the testes, is the most important androgen for boys; it is responsible for the sexual development and maturation that occurs during puberty.

Estrogens are female-type sex hormones, produced mainly by the ovaries. Estrogens trigger breast development and the sexual maturation process that results in menstrual periods. Boys also produce low levels of estrogens in their testes.

Together, androgens and estrogens interact with growth hormone to cause the characteristic "growth spurt" seen at puberty.

Cortisol is another important hormone produced by the adrenal glands. It helps maintain normal blood pressure and blood glucose. Cortisol is released into the bloodstream at higher levels in response to physical stresses such as infection, fever, injury, surgery and severe emotional stress.

Insulin, which is produced in the pancreas, helps the body use carbohydrates (sugars and starches) for energy. When insulin levels are insufficient, diabetes may develop.