What is short stature, and is it treatable?
Short stature can be a variant of normal growth, or it may indicate a disorder or condition.
Growth rate is an important indicator of overall health. Children who do not reach the 5th percentile by the age of 5 years are said to be small for gestational age (SGA). A pediatrician will look out for signs of "failure to thrive."
Early intervention can prevent future problems in many cases.
Normally, at 8 years of age, a child's arm span is around the same as their height. If these measurements are out of proportion, this may be a sign of disproportionate short stature (DSS), sometimes known as "dwarfism."
Here are some key points about short stature. More detail is in the main article.
- Short stature can happen for a wide range of reasons, including having small parents, malnutrition, and genetic conditions such as achondroplasia.
- Proportionate short stature (PSS) is when the person is small, but all the parts are in the usual proportions. In disproportionate short stature (DSS), the limbs may be small compared with the trunk.
- If short stature results from a growth hormone (GH) deficiency, GH treatment can often boost growth.
- Some people may experience long-term medical complications, but intelligence is not usually affected.
Growth depends on a complex range of factors, including genetic makeup, nutrition, and hormonal influences.
Short stature can run in families or it can result from a hormone deficit or a genetic change.
The most common cause of short stature is having parents whose height is below average, but around 5 percent of children with short stature have a medical condition.
Conditions that can underlie short stature include:
- undernutrition, due to a disease or lack of nutrients
- hypothyroidism, leading to a lack of growth hormone
- a tumor in the pituitary gland
- diseases of the lungs, heart, kidneys, liver, or gastrointestinal tract
- conditions that affect the production of collagen and other proteins
- some chronic diseases, such as celiac disease and other inflammatory disorders
- mitochondrial disease, which can affect the body in different ways, including growth
Sometimes, an injury to the head during childhood can lead to reduced growth.
A lack of growth hormone can also lead to delayed or absent sexual development.
Rheumatologic diseases, such as arthritis, are linked to short stature. This may happen because of the disease, or as a result of the glucocorticoid treatment, which can affect the release of growth hormone.
Disproportionate short stature (DSS) usually stems from a genetic mutation that affects the development of bone and cartilage and undermines physical growth.
The parents may not have short stature, but they may pass on a condition that is linked to DSS, such as achondroplasia, mucopolysaccharide disease, and spondyloepiphyseal dysplasia (SED).
There are different types and causes of short stature, or restricted growth, and they will present differently. Because the range of conditions is so broad, restricted growth can be classified in various ways.
One categorization is:
- Variant restricted growth
- Proportionate short stature (PSS)
- Disproportionate short stature (DSS)
Each of these categories includes a number of types and causes of short stature.
Variant restricted growth
Sometimes a person is small but otherwise healthy. This can be referred to as variant restricted growth. It may happen for genetic or hormonal reasons.
If the parents are also small, this can be called familial short stature (FSS). If it stems from a hormonal issue, it is a constitutional delay in growth and adolescence (CDGA).
The limbs and the head develop in proportion with the spine, and the individual is otherwise healthy.
Growth happens throughout the body, so the legs, for example, are in proportion with the spine.
In most cases, the individual's parents are also small, but sometimes small stature happens because the body does not produce enough growth hormone (GH), or the body does not process growth hormone properly. This is known as GH insensitivity. Hypothyrodism can lead to low hormone production.
Growth hormone treatment during childhood may help.
Proportionate short stature (PSS)
Sometimes, overall growth is restricted, but the person's body is in proportion, and the individual has a related health problem. This is known as proportionate short stature (PSS).
If the individual is heavy for their height, this can suggest a hormone problem. The problem could be hypothyroidism, excess glucorticoid production, or too little GH.
A person who is small and their weight is low for their height may be experiencing malnutrition, or they may have a disorder that leads to malabsorption.
Whatever the underlying reason, if it affects overall growth, it may impact development in at least one body system, so treatment is needed.
During adulthood, a person with this type of restricted growth is more likely to experience:
- cardiovascular problems
- reduced muscle strength
Rarely, there may be cognitive problems, or problems with thinking. This depends on the cause of the short stature.
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Disproportionate short stature (DSS)
Disproportionate short stature (DSS) is linked to a genetic mutation. The parents are usually of average height. As with other types of short stature, a range underlying causes is possible.
Disproportionate short stature can result from a genetic condition.
An individual with DSS will be small in height, and they will have other unusual physical features. These may be visible at birth, or they may develop in time as the infant develops.
Most individuals will have an average-sized trunk and short limbs, but some people may have a very short trunk and shortened, but disproportionately large limbs. Head size may be disproportionately large.
Intelligence or cognitive abilities are unlikely to be affected unless the person has hydrocephalus, or too much fluid around the brain.
Achondroplasia underlies around 70 percent of cases of DSS. It affects around 1 in 15,000 to 1 in 40,000 people.
- an average-sized trunk
- short limbs, especially the upper arms and legs
- short fingers, possibly with a wide space between the middle and ring fingers
- limited mobility in the elbows
- a large head with a prominent forehead and flattened bridge of the nose
- bowed legs
- lordosis, a progressive development of a swayed lower back
- average adult height of 4 feet, or 122 cm
Hypochondroplasia is a mild form of achondroplasia. It may be difficult to differentiate between familial short stature and achondroplasia.
Achondroplasia and hypochondroplasia result from a genetic mutation.
Genetic conditions, such as Turner syndrome, Down syndrome, or Prader Willi syndrome, are also linked to DSS.
Some types of short stature can be diagnosed at birth. In other cases, routine visits to a pediatrician should reveal any abnormal growth pattern.
The doctor will record the child's head circumference, height, and weight.
If the doctor suspects restricted growth, they will carry out a physical examination, look at the child's medical and family history, and possibly carry out some tests.
These may include:
An x-ray, to assess for problems with bone development
An insulin tolerance test, to check for a deficiency in the growth hormone insulin-like growth factor-1 (IGF-1).
In this test, insulin is injected into a vein, causing blood glucose levels to drop. Normally, this would trigger the pituitary gland to release growth hormone (GH). If GH levels are lower than normal, there may be a GH deficiency.
Other tests include:
- a thyroid-stimulating hormone test, to check for hypothyroidism
- a complete blood count, to test for anemia
- metabolic tests, to assess liver and kidney function
- erythrocyte sedimentation and C-reactive protein tests, to assess for inflammatory bowel disease
- urine tests can check for enzyme deficiency disorders
- tissue transglutinase and immunoglobulin A tests, for celiac disease
- imaging scans, such as an x-ray of the skeleton and the skull or an MRI, can detect problems with the pituitary gland or hypothalamus
- bone marrow or skin biopsies may help confirm conditions associated with short stature
Treatment will depend on the cause of the short stature.
Growth hormone can treat some types of short stature.
If there are signs of malnutrition, the child may need nutritional supplements or treatment for a bowel disorder or other condition that is preventing them from absorbing nutrients.
If growth is restricted or delayed because of a hormonal problem, GH treatment may be necessary.
Pediatric hormone treatment: In children who produce too little GH, a daily injection of hormone treatment may stimulate physical growth later in life. Medications, such as somatropin, may eventually add 4 inches, or 10 centimeters, to adult height.
Adult hormone treatment: Treatment for adults can help protect against complications, for example, cardiovascular disease and low bone mineral density.
Somatropin, also known as recombinant GH, might be recommended for people who:
- have a severe growth hormone deficiency
- experience impaired quality of life
- are already receiving treatment for another pituitary hormone deficiency
Adult patients generally self-administer daily with an injection.
The patient may receive treatment to control chronic conditions, such as heart disease, lung disease, and arthritis.
Treatment for DSS
As DSS often stems from a genetic disorder, treatment focuses mainly on the complications.
Some patients with very short legs may undergo leg lengthening. The leg bone is broken and then fixed into a special frame. The frame is adjusted daily to lengthen the bone.
This does not always work, it takes a long time, and there is a risk of complications, including:
- the bone forming badly or at an inappropriate rate
- deep vein thrombosis (DVT), a blood clot in a vein
Other possible surgical treatments include:
- use of growth plates, where metal staples are inserted into the ends of long bones where growth takes place, to help bones grow in the right direction
- inserting staples or rods to help the spine form the right shape
- increasing the size of the opening in the bones of the spine to reduce pressure on the spinal cord
Regular monitoring can reduce the risk of complications.
A person with DSS may experience a number of complications.
- arthritis later in life
- delayed mobility development
- dental problems
- bowed legs
- hearing problems and otitis media
- hydrocephalus, or too much fluid in the brain cavities
- hunching of the back
- limb problems
- swaying of the back
- narrowing of the channel in the lower spine during adulthood and other spine problem
- sleep apnea
- weight gain
- speech and language problems
Individuals with proportionate short stature (PSS) may have poorly developed organs and pregnancy complications, such as respiratory problems. Delivery will normally be by cesarean section.
Most people with short stature will have a normal life expectancy, and 90 percent of children who are small for their age at 2 years will "catch up" by adulthood.
The 10 percent who do not catch up are likely to have a condition such as fetal alcohol, Prader-Willi, or Down syndrome.
A person with achondroplasia can also expect a normal lifespan
However, some serious conditions that are linked to some cases of short stature can be fatal.