Children's growth depends on a wide range of factors

Donya Betancourt, Pediatrician, Sanur, Bali, drdonya@hotmail.com

Parents and loved ones are often curious about the projected growth of children, and ask questions like "How tall will my two- year-old be when he grows up?"

Parents are typically more concerned when their children are shorter than their peers, although the fact is, most short children fall within the normal range of height.

This article is the first part of a three-part series on children's growth. This week we will learn about short stature and tall stature.

Growth assessment is an essential component of children health surveillance. Growth is an index of general health, nutrition and genetics. The most powerful tool in growth assessment is the growth chart. Most of us end up with about the same build as our parents.

The normal length of a baby is about 50 cm long at birth, with rapid growth occurring during the first year of life.

Most infants grow as much as 25 cm over the first year to reach about 75 cm at one year old. During the second year of life, growth is half as rapid.

The average child grows about 13 cm between its first and second birthday so that at two years of age, the child will be about 87.5 cm tall. After two years of age, growth continues at a slower but steady rate of five to six centimeters per year until about the age of 11 in girls and 13 in boys -- when the growth spurt that goes along with adolescence usually begins.

This puberty growth spurt usually lasts two years and is accompanied by sexual development. Growth ceases between 16 and 18 years of age. Once growth ends, the bones fuse.

What determines how a child grows? How is height inherited?

A person's growth is influenced by many factors including heredity, nutrition and environment, as well as other physical and psychological factors. Optimal growth requires optimal health and nutrition.

If a person is malnourished, has lung problems, was born with a genetic disorder or suffers from a number of other medical conditions, growth can be affected.

In general, growth is the result of the interactions of hormones in the body's endocrine system. The endocrine glands secrete hormones to control physical growth, sexual function and metabolism. The major glands of the endocrine system include the pituitary, thyroid, parathyroid and adrenal glands, pancreas (which produces insulin); and the testes and ovaries.

The master gland "pituitary" lies at the base of the skull and controls many other glands. It produces many hormones, including the "growth hormone". It stimulates the development of muscles and bones and also helps regulate the metabolism. If the pituitary gland produces inadequate amounts of growth hormone, it will result in abnormally slow growth and short stature.

The thyroid gland produces thyroid hormones to control metabolism and growth. If the thyroid cannot produce an adequate amount of hormone, hypothyroidism develops. When beginning in childhood, the result will be slow growth and will affect other bodily functions.

The adrenal glands are above the kidney in the lower back and produce many hormones including androgens, which are male sex hormones. If a high androgen level is present in young boys, growth is accelerated and the bones mature faster than normally, but finish growing earlier -- resulting in short final height.

Sex organs in male testes produce testosterone and sperm. They can underfunction, which is called hypogonadism, or the pituitary gland stops stimulating them. When this happens, growth and sexual development may be retarded.

In females, the ovaries produce estrogen. If it is not produced adequately, the result will be delays in growth and sexual development, called turner syndrome.

As you can see, the hormones of the endocrine systems when inadequate can cause a variety of problems, including growth delay or failure. If produced in excess amounts it can also cause growth disorder like gigantism. It is important to identify and treat these problems early so that normal growth and development can occur.

How do you know if your child is experiencing delayed growth? What are the signs of growth failure? How are growth problems treated? The questions will be addressed next week.