Highlights
- Circulating hyperghrelinemia is confirmed as a specific biomarker of Prader-Willi Syndrome (PWS) rather than a general feature of rare genetic neurodevelopmental disorders (NDDs).
- Non-PWS rare NDD patients exhibit ghrelin levels comparable to patients with simple obesity, despite presenting with high scores of hyperphagia.
- Hyperphagia in children with rare NDDs is more prevalent and severe than in children with PWS, indicating distinct underlying pathophysiological mechanisms.
- Caregiver burden, measured by the Zarit Burden Interview (ZBI), is significantly high in families of patients with rare NDDs and is directly correlated with the severity of the patient’s hyperphagia.
Background
Rare genetic neurodevelopmental disorders (NDDs) encompass a heterogeneous group of conditions characterized by cognitive impairment, behavioral challenges, and frequently, metabolic disturbances. Among these, hyperphagia—an insatiable drive for food—and subsequent obesity represent major clinical hurdles. Historically, Prader-Willi Syndrome (PWS) has served as the archetype for genetic hyperphagia, largely due to its unique endocrine hallmark: significantly elevated circulating levels of ghrelin, the ‘hunger hormone.’
While the association between PWS and hyperghrelinemia is well-established, it has remained unclear whether other rare genetic NDDs that share phenotypic similarities (e.g., intellectual disability, obesity, and hyperphagia) also exhibit this hormonal profile. Understanding whether hyperghrelinemia is a universal feature of NDD-related hyperphagia is critical for both diagnostic accuracy and the development of targeted pharmacological interventions. Furthermore, the psychosocial impact of hyperphagia on families remains an under-addressed area of clinical care, necessitating a multidimensional approach to assessment.
Key Content
Comparative Endocrine Analysis: Ghrelin as a Specific Biomarker
Recent evidence from a large-scale, national multicenter study (Diene et al., 2026) involving 130 patients with 27 distinct genetic NDDs has provided definitive clarity on the specificity of ghrelin. The study analyzed total ghrelin, acylated ghrelin (AG), and unacylated ghrelin (UAG) across diverse populations including children and adults with NDDs, and compared them against controls including PWS patients, obese non-NDD individuals, and lean subjects.
Findings indicated that median total ghrelin levels in rare NDDs (76.7 pg/mL) were significantly lower than those found in the PWS group (p<0.001). Crucially, these levels were statistically indistinguishable from the 'Obese' control group. This suggests that the hyperghrelinemia observed in PWS is a unique consequence of the 15q11-q13 deletion or uniparental disomy, rather than a secondary result of the neurodevelopmental status or the hyperphagic phenotype itself. Consequently, total ghrelin and its isoforms (AG/UAG) should be considered specific biomarkers for PWS in the differential diagnosis of genetic obesity.
Hyperphagia Severity: A Surprising Childhood Prevalence
Using the Hyperphagia Questionnaire (HQ), researchers assessed the intensity and frequency of food-seeking behaviors. A pivotal finding of the recent cross-sectional data is that children with rare NDDs (mean score 26.3) actually exhibit higher hyperphagia scores than children with PWS. This suggests that in the pediatric NDD population, the behavioral drive to eat may be even more intense than in the syndrome classically associated with the condition.
Conversely, in the adult population, the trend reversed: adults with NDDs (mean score 24.0) showed lower hyperphagia scores compared to adults with PWS. This divergence suggests that the natural history of hyperphagia may evolve differently across life stages in various genetic conditions, potentially due to differences in the maturation of hypothalamic satiety pathways or the implementation of external dietary controls.
The Correlated Impact on Caregiver Well-being
One of the most clinically relevant aspects of recent NDD research is the quantification of caregiver burden. Using the Zarit Burden Interview (ZBI), studies have shown mean scores of approximately 37.8 in children and 37.6 in adults with NDDs. These scores indicate a ‘moderate to severe’ burden.
Statistical analysis reveals a strong positive correlation between HQ total scores and ZBI scores. This highlights that hyperphagia is not just a metabolic or nutritional issue, but a primary driver of familial stress. The constant vigilance required to prevent food-seeking, manage weight, and handle behavioral outbursts related to food significantly degrades the quality of life for the entire household. This underscores the need for clinical guidelines to include caregiver support as a standard component of NDD management.
Expert Commentary
The realization that hyperphagia in non-PWS NDDs occurs in the presence of ‘normal’ (obese-range) ghrelin levels shifts the focus from peripheral hormonal signals to central nervous system (CNS) dysfunction. In many rare NDDs, the pathophysiology of hyperphagia likely resides in the leptin-melanocortin pathway or other hypothalamic satiety circuits rather than the stomach-derived ghrelin signal.
From a clinical perspective, this suggests that ghrelin-receptor antagonists, which are currently being investigated for PWS, may have limited efficacy in other rare genetic NDDs. Instead, clinicians should look toward interventions targeting central satiety mechanisms, such as GLP-1 receptor agonists or MC4R agonists, depending on the specific genetic underlying cause. Furthermore, the higher severity of hyperphagia in NDD children compared to PWS children suggests that early screening and behavioral intervention are even more urgent in the broader NDD population than previously recognized.
Conclusion
In conclusion, while rare genetic neurodevelopmental disorders often present with a phenotype of hyperphagia and obesity similar to Prader-Willi Syndrome, their underlying biology is distinct. Hyperghrelinemia remains a unique biomarker of PWS. The discovery that children with various NDDs suffer from more severe hyperphagia than their PWS counterparts, and that this behavior is a primary driver of caregiver burden, necessitates a shift in clinical priority. Future research should focus on identifying the specific central pathways disrupted in each rare genetic condition to facilitate personalized metabolic care and alleviate the profound burden on families.
