Effect of Growth Hormone Therapy in Patients with Noonan Syndrome: A Retrospective Study

Efficacy and safety of growth hormone therapy in children with Noonan syndrome

Patients with Noonan syndrome typically have a target height <2 standard deviations compared to the general population, and half of the affected adults remain permanently below the 3rd centile for height, though their short stature might result from a multifactorial etiology, not-yet fully understood. The secretion of growth hormone (GH) following the classic GH stimulation tests is often normal, with baseline insulin-like growth factor-1 (IGF-1) levels at the lower normal limits, but patients with Noonan syndrome have also a possible moderate response to GH therapy, leading to a final increased height and substantial improvement in growth rate. Aim of this review was to evaluate both safety and efficacy of GH therapy in children and adolescents with Noonan syndrome, also evaluating as a secondary aim the possible correlations between the underlying genetic mutations and GH responses.

The Effect of Growth Hormone Therapy on Cardiac Outcomes in Noonan Syndrome: Long Term Follow-up Results

OBJECTIVE

Cardiac involvement is common in Noonan syndrome (NS). Concerns have been raised regarding the effect of recombinant growth hormone (rGH) use on ventricular wall thickness and a possible increased risk of cardiac side effects. This study aimed to investigate the effect of rGH on the development of hypertrophic cardiomyopathy and other cardiac findings in NS.

METHODS

Patients under the age of 18 years and diagnosed with NS according to the Van der Burgt criteria, were included. Patients were divided into two groups according to those receiving rGH or not at the time of obtaining cardiac measurements. Before and after the treatment, electrocardiographic and echocardiographic (ECHO) assessments were made, including interventricular septal thickness, left ventricular internal diameter, and left ventricular posterior thickness. Results were expressed as Z scores.

RESULTS

Twenty-four NS subjects (16 boys, eight girls) were included. At the beginning of the follow up, the overall height standard deviation score was -2.56±0.94. Sixteen were on rGH. The mean rGH treatment duration was 8.3±3.8 years, and the mean dose was 0.22±0.04 mg/kg/week. The final height was 169±8.2 cm, and 10 of 11 patients who reached the final height received rGH. There was no difference between the rGH and non-rGH groups in terms of ECHO parameters pre-and post-treatment.

CONCLUSION

In this cohort, there was no change in ECHO parameters on rGH and during follow-up. These results suggest that rGH is safe in NS patients with cardiac pathology under close follow-up.

Genetic conditions of short stature: A review of three classic examples

Noonan, Turner, and Prader-Willi syndromes are classical genetic disorders that are marked by short stature. Each disorder has been recognized for several decades and is backed by extensive published literature describing its features, genetic origins, and optimal treatment strategies. These disorders are accompanied by a multitude of comorbidities, including cardiovascular issues, endocrinopathies, and infertility. Diagnostic delays, syndrome-associated comorbidities, and inefficient communication among the members of a patient's health care team can affect a patient's well-being from birth through adulthood. Insufficient information is available to help patients and their multidisciplinary team of providers transition from pediatric to adult health care systems. The aim of this review is to summarize the clinical features and genetics associated with each syndrome, describe best practices for diagnosis and treatment, and emphasize the importance of multidisciplinary teams and appropriate care plans for the pediatric to adult health care transition.

Inside the Noonan "universe": Literature review on growth, GH/IGF axis and rhGH treatment: Facts and concerns

Noonan syndrome (NS) is a disorder characterized by a typical facial gestalt, congenital heart defects, variable cognitive deficits, skeletal defects, and short stature. NS is caused by germline pathogenic variants in genes coding proteins with a role in the RAS/mitogen-activated protein kinase signaling pathway, and it is typically associated with substantial genetic and clinical complexity and variability. Short stature is a cardinal feature in NS, with evidence indicating that growth hormone (GH) deficiency, partial GH insensitivity, and altered response to insulin-like growth factor I (IGF-1) are contributing events for growth failure in these patients. Decreased IGF-I, together with low/normal responses to GH pharmacological provocation tests, indicating a variable presence of GH deficiency/resistance, in particular in subjects with pathogenic PTPN11 variants, are frequently reported. Nonetheless, short- and long-term studies have demonstrated a consistent and significant increase in height velocity (HV) in NS children and adolescents treated with recombinant human GH (rhGH). While the overall experience with rhGH treatment in NS patients with short stature is reassuring, it is difficult to systematically compare published data due to heterogeneous protocols, potential enrolment bias, the small size of cohorts in many studies, different cohort selection criteria and varying durations of therapy. Furthermore, in most studies, the genetic information is lacking. NS is associated with a higher risk of benign and malignant proliferative disorders and hypertrophic cardiomyopathy, and rhGH treatment may further increase risk in these patients, especially as dosages vary widely. Herein we provide an updated review of aspects related to growth, altered function of the GH/IGF axis and cell response to GH/IGF stimulation, rhGH treatment and its possible adverse events. Given the clinical variability and genetic heterogeneity of NS, treatment with rhGH should be personalized and a conservative approach with judicious surveillance is recommended. Depending on the genotype, an individualized follow-up and close monitoring during rhGH treatments, also focusing on screening for neoplasms, should be considered.