What Causes Human Growth?

Growth Defined

Physical growth can best be defined as increases in a child's height and weight beginning at birth and continuing throughout adolescence into the teen years. Although children grow at different rates, most teens reach physical maturity by age 15 to 17. Girls typically finish growing sooner than boys. Measures of height and weight are used to assess a child's growth. Sometimes body mass index (BMI) may also be compared to height by dividing the child's weight by his height. BMI in relation to height indicates whether a child is overweight or underweight, or developing within normal ranges.

Growth Rate

As a child grows, her bones grow longer. Cells in the body grow larger and then divide into more cells, producing new cartilage inside the bones. These layers of cartilage eventually form into bone that lengthens the existing bone. Although most babies grow an average of 10 inches in length during their first year of life, by the time they go to school their growth rate slows to only 2 inches each year. Two major growth spurts occur in a child's life. The first is during infancy and then again at the onset of puberty. A youth may grow as many as 4 inches in one year. After a year or two and toward the end of puberty, the growth rate slows again.

Genetics

Genes play a major role in regulating growth. According to an article published in the November 2008 issue of "Growth, Genetics & Hormones Journal," genes are primarily responsible for determining a child's growth pattern.

Because most children grow to a height similar to that of their parents, how tall a person grows in stature is affected by a number of different genes that contribute to the functions of the endocrine system. The pituitary gland produces and secretes human growth hormone, which affects a child's bone development and height.

Nutrition

Poor nutrition during a child's first two years can slow growth and development, as children who are malnourished fail to thrive. Eating a balanced diet that includes essential vitamins and minerals is needed for proper growth. Depending on a child's age, the amount of protein, carbohydrates and fat that children need for healthy growth changes. While the number of grams of protein increases, as a child grows older, the percentage of total daily calories that come from fat should decrease. Carbohydrates consumed basically remain the same throughout childhood, whereas calcium intake needed for strong bones increases significantly after age 4.

Hormones

Human growth hormone has a significant role in the development of the skeletal bones and tissue. The hormone also has an effect on the body's muscle and fat cells. However, there are several other hormones that contribute to growth. Somatotropins, proteins secreted by the anterior pituitary gland, play a part in DNA synthesis along with contributing to cartilage and collagen formation. Insulin, thyroid hormones, estrogens and glycocorticoids are other hormones that are necessary for children to grow normally by regulating the production of growth hormone.