Laron syndrome

What causes Laron syndrome?

Laron syndrome is caused by changes (mutations) in the GHR gene. This gene encodes growth hormone receptor, which is a protein found on the outer membrane of cells throughout the body. Growth hormone receptor is designed to recognize and bind growth hormone, which triggers cellular growth and division. When growth hormone is bound to the growth hormone receptors on liver cells, specifically, insulin-like growth factor I (another important growth-promoting hormone) is produced. Mutations in GHR impair the function of growth hormone receptors which interferes with their ability to bind growth hormone. This disrupts normal growth and development of cells and prevents the production of insulin- like growth factor I which causes the many signs and symptoms of Laron syndrome.

Last updated on 05-01-20

How is Laron syndrome diagnosed?

A diagnosis of Laron syndrome is often suspected based on the presence of characteristic signs and symptoms. Additional testing can then be ordered to confirm the diagnosis and rule out other conditions that cause similar features. This generally includes blood tests to measure the levels of certain hormones that are often abnormal in people with Laron syndrome. For example, affected people may have elevated levels of growth hormone and reduced levels of insulin-like growth factor I. Genetic testing for changes (mutations) in the GHR gene can also be used to confirm a diagnosis in some cases.

Last updated on 05-01-20

Is Laron syndrome inherited?

Most cases of Laron syndrome are inherited in an autosomal recessive manner. This means that to be affected, a person must have a mutation in both copies of the responsible gene in each cell. The parents of an affected person usually each carry one mutated copy of the gene and are referred to as carriers. Carriers typically do not show signs or symptoms of the condition. When two carriers of an autosomal recessive condition have children, each child has a 25% (1 in 4) risk to have the condition, a 50% (1 in 2) risk to be a carrier like each of the parents, and a 25% chance to not have the condition and not be a carrier.

Reports exist of rare families in which Laron syndrome appears to be inherited in an autosomal dominant manner. In these cases, a person only needs a change (mutation) in one copy of the responsible gene in each cell. In some cases, an affected person inherits the mutation from an affected parent. Other cases may result from new (de novo) mutations in the gene. These cases occur in people with no history of the disorder in their family. An affected person has a 50% chance with each pregnancy of passing along the altered gene to his or her child.

Last updated on 05-01-20

What is the long-term outlook for people with Laron syndrome?

The long-term outlook (prognosis) for people with Laron syndrome is generally good. The condition does not appear to affect lifespan and is associated with a reduced risk of cancer and type 2 diabetes.

Last updated on 05-01-20

How might Laron syndrome be treated?

There is currently no cure for Laron syndrome. Treatment is primarily focused on improving growth. The only specific treatment available for this condition is subcutaneous injections of insulin-like growth factor 1 (a growth-promoting hormone), often called IGF-1. IGF-1 stimulates linear growth (height) and also improves brain growth and metabolic abnormalities caused by long-term IGF-1 deficiency. It has also been shown to raise blood glucose levels, reduce cholesterol, and increase muscle growth. IGF-1 and GH levels should be closely monitored in people undergoing this treatment because overdosage of IGF-I causes a variety of health problems.

Last updated on 05-01-20

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