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Growth During Childhood

by Dr. Vera Oh

Children grow very rapidly the first two years of life followed by a period of more moderate growth during their childhood years. They have another growth spurt during the teenage years as they approach puberty. This is reflected by a rapid weight and height gain.

Weight changes:

• Loss of 5-10% of birth weight the first few days of life

• Week 1 - 2 : Regain birth weight

• 2 weeks - 3months : Gain 20 - 30g /day

• 3 - 6 months : Gain 20g /day

• 6 -12 months : Gain 12g /day

• 12 -18 months : Gain 8 g /day

Generally, children double their birth weight by 5-6 months of age and triple their birth weight by 1 year.

Height gained:

1st year: 25cm

2nd year: 12cm

3rd year onwards till puberty: 6 cm/y

Growth spurt during puberty ( usually of about 2 years duration) :

Girls 6-11 cm/ y

Boys 7-12 cm/y

Factors that affect growth

A child’s height is influenced by genetics, general health, nutrition, hormones and his psychosocial environment.

The final height is usually close to the average of the parental heights. In a boy, it is the average of the parents’ heights plus an additional 6.5cm. In girls, the final height is the average of the parents’ heights minus 6.5cm.

Genetic or chromosomal abnormalities may affect height adversely. Conditions like Prader- Willi syndrome, Russell-Silver and Turner syndrome result in short stature.

Hormone problems like hypothyroidism, hyperthyroidism or growth hormone deficiency impact on growth. Likewise, chronic illnesses contribute to short stature. For example, a child with poorly controlled asthma, chronic diarrhoea or an unaddressed cardiac condition would appear short relative to his peers.

Monitoring a child’s growth

To track a child’s growth, plot his weight and height on the growth charts found in the health and immunization booklet. Over time, these growth points form a curve and give an indication of how the child compares with his peers. If a boy’s weight falls on the 25th centile line, he is heavier than 25% of normal boys his age and lighter than 75% of normal boys.

After 2 years of age, most children grow in tandem with their peers so their growth curves appear parallel to the standardized centile lines. Between the age of 6-18 months, however, some children may appear to move up or down the charts relative to their cohort. Shifts during this period may be normal if there is continued weight gain (never weight loss) and the child is in good health.

Red Flags – When We Should Be Concerned

Children whose measurements fall under the 3rd centile should be assessed by their paediatrician. This is especially so if they have chronic diarrhoea, vomiting, poor appetite or have delayed milestones.

Another cause for concern is the child who fails to gain weight or height appropriately. Most children after the age of 2 years grow consistently 6cm a year until puberty, during which time there is a growth spurt. A child who grows too slowly appears to start off at a higher centile and falls to a lower centile over time. This is reflected on the growth chart by a child’s curve cutting across the standardized centile lines.

Growth Assessment

During a visit to the doctor, many questions will be asked about the growth, general health, nutrition as well as the birth and development of your child. She will also take notes about family history and the heights of the parents and siblings. A thorough physical examination will be carried out. This includes looking at the weight, height measurements, pubertal stage and aims at detecting any relevant medical conditions.

Previous height and weight measurements of the child are useful in determining his growth rate. It is important to see if the child is keeping up with his peers and growing at a normal rate.

Diagnosis

Depending on the findings in clinic, the doctor may recommend further tests which may include:

Bone age - This is an X-ray of the wrist and gives the doctor an indication of the skeletal maturity of your child. Some children may have bones younger or older than their chronological ages and this will have bearing on their height.

Karyotype - In the instance of short girls, the doctor may ask for an analysis of their chromosomes. This is to exclude a condition known as Turner syndrome. ( See below).

Growth hormone stimulation test -

Random levels of growth hormone do not reflect the body's true ability to produce growth hormone. In order to detect growth hormone deficiency, a growth hormone stimulation test is conducted. Not all patients require a growth hormone stimulation test and this is only carried out if indicated.

Management

For a child to grow well, he needs a balanced diet. Chronic illnesses or hormone deficiencies need to be identified and adequately treated.

Growth hormone has been approved for the treatment of growth hormone deficiency, short stature in chronic renal insufficiency, Turner syndrome, Prader-Willi syndrome, children who were small for gestational age at birth and fail to catch-up, SHOX deficiency and Idiopathic Short Stature. In appropriate cases, the use of growth hormone can improve the final height outcome.

Conditions Associated with Short Stature

Growth Hormone Deficiency (GHD)

Children with GHD do not have normal production of growth hormone (GH). This may be due to a developmental abnormality of the pituitary gland that is normally in charge of producing GH. In some children, the pituitary gland may have been destroyed by infection or tumours. In others, there is no structural abnormailty of the pituitary gland but it just fails to perform normally. Sometimes, GHD is associated with other hormone deficiencies as well.

Children with GHD fail to grow normally and do benefit from growth hormone treatment. This should however, first be assessed by and discussed with your doctor.

Turner syndrome

Girls generally have two copies of the X chromosomes in each of their cells. Turner syndrome is a genetic condition where there is a missing X chromosome in some or all of the cells. Girls with Turner syndrome are short and may also have other distinctive physical features. GH helps these girls grow better. Often, these girls also have problems of delayed puberty and require female hormone replacement.

Intrauterine Growth Retardation (IUGR) or Small for Gestational Age ( SGA).

Some babies grow suboptimally while in the womb. This may have been due to maternal health issues, a placenta that did not function well, the baby's genes or other unknown factors. These children are small at birth compared to their peers of the same “incubation period”. For term babies, this is usually taken to be birth weights of less than 2.5kg, or lengths of less than 45cm. Most of these children, despite being born small, will catch up with their friends by 2-3 years of age. Those who do not catch up may benefit from GH treatment.

There is information that SGA children are at increased risk of high blood pressure, insulin resistance, lipid problems and metabolic syndrome in later adult life. These issues need to be discussed before a decision is made with regard growth and GH treatment.

Constitutional Delay of Growth and Development

This is a term used to describe late-bloomers who enter puberty later than their peers. There is often a family history of similar pubertal delay in their parents and close relatives. As a result of their less mature skeletal system, they may appear shorter than their classmates initially. They start puberty late but may grow for a longer time and catch up with their peers. Because these are normal children, most of them will finish off within the normal height range as dictated by their genetic potential.

Idiopathic Short Stature

Idiopathic is simply a medical term for “unknown cause”. These are children who are very short but who appear to be healthy otherwise. They have normal hormone levels and are not GH deficient when tested. There is now evidence that some these children may have other genetic factors that contribute to their short stature.

GH has been to shown to help improve the growth of some of these children.