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Laron syndrome
A disorder caused by growth hormone receptor mutation resulting in short stature.
Overview
Laron syndrome, also known as growth hormone insensitivity syndrome, is a rare genetic disorder characterized by an inability of the body to respond to growth hormone (GH). Despite normal or elevated levels of GH, affected individuals have very low levels of insulin-like growth factor 1 (IGF-1), which is necessary for growth and development. As a result, patients with Laron syndrome experience severe short stature (dwarfism), delayed skeletal development, and distinct facial features. The condition is typically identified in early childhood due to poor growth velocity.
Causes
Laron syndrome is caused by mutations in the GHR gene, which encodes the growth hormone receptor. These mutations prevent the receptor from functioning properly, thereby blocking the GH signaling pathway and preventing the production of IGF-1. The condition is inherited in an autosomal recessive pattern, meaning a child must inherit two defective copies of the gene (one from each parent) to develop the disorder. The syndrome is more commonly reported in certain populations with higher rates of consanguinity or genetic isolation, such as in some regions of Ecuador and the Middle East.
Symptoms
The symptoms of Laron syndrome typically become apparent in infancy or early childhood and may include:
Severe short stature – height significantly below average for age and sex
Delayed skeletal maturation – including underdeveloped bones and delayed dental eruption
Distinct facial features – including a prominent forehead, depressed nasal bridge, and small jaw (micrognathia)
Obesity or increased body fat – particularly around the abdomen
Small hands and feet
Delayed puberty
Hypoglycemia – episodes of low blood sugar, particularly in infancy
Diagnosis
Diagnosis of Laron syndrome involves a combination of clinical findings, hormone testing, and genetic analysis. Key diagnostic steps include:
Measurement of growth hormone (GH) – typically normal or elevated levels
Measurement of IGF-1 – significantly low despite normal GH
IGF-1 generation test – shows failure to increase IGF-1 levels after GH administration
Radiographic assessment – to evaluate bone age and skeletal development
Genetic testing – to confirm mutations in the GHR gene
Treatment
Treatment for Laron syndrome focuses on replacing the deficient IGF-1 hormone to promote growth and development. Main therapeutic strategies include:
Recombinant IGF-1 therapy (mecasermin) – administered via daily subcutaneous injections to stimulate growth in children
Monitoring for side effects – such as hypoglycemia, which can occur especially early in treatment
Nutritional and metabolic support – to manage weight and blood sugar levels
Endocrine evaluation – particularly during adolescence to monitor puberty and hormone levels
Growth hormone therapy is ineffective in Laron syndrome due to the insensitivity of the GH receptor.
Prognosis
The long-term outlook for individuals with Laron syndrome varies. While affected individuals typically remain short in stature, early initiation of IGF-1 therapy can improve height outcomes, metabolic function, and overall quality of life. Importantly, people with Laron syndrome have been observed to have a lower incidence of cancer and type 2 diabetes, potentially due to their unique hormonal profile. With appropriate medical care and support, individuals with Laron syndrome can lead relatively healthy and productive lives.
Medical Disclaimer
The information provided on this page is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.