The goal of this observational study is to investigate cellular mechanisms of neuroendocrine and metabolic signaling in adult women with anorexia nervosa (AN) compared to healthy controls. The primary purpose is to understand how hypothalamic-like neurons derived from patient samples respond to metabolic hormones and regulate energy homeostasis.

The main questions it aims to answer are:

Do hypothalamic-like neurons derived from individuals with AN show altered responsiveness to key metabolic hormones compared to neurons derived from healthy controls? Are there differences in cellular metabolism, gene expression profiles, and neuronal activity that reflect disease-relevant neuroendocrine dysfunction? Researchers will compare patient-derived cellular models from individuals with AN to those generated from matched healthy control participants to determine whether differences in hormone responsiveness, metabolic function, and neuronal signaling can be identified.

Participants will:

Attend a single study visit at a recruiting clinical site Provide a small peripheral blood sample Undergo basic clinical assessment and anthropometric measurements Collected samples will be coded at the recruiting sites and transferred to a central research laboratory, where they will be used to generate induced pluripotent stem cells (iPSCs) and differentiate them into hypothalamic-like neurons. All experimental analyses are conducted in vitro and do not involve any intervention or treatment administered to participants.

Inclusion Criteria:

Female participants aged 18-45 years (premenopausal) Diagnosis of severe and enduring anorexia nervosa (illness duration ≥7 years, with documented functional impairment and non-response to appropriate treatments) Current BMI ≤18.5 kg/m² or documented BMI ≤18.5 kg/m² within the past 12 months Ability to provide informed consent Sufficient proficiency in the study language (German)

For healthy controls:

Female participants aged 18-45 years BMI between 18.5 and 24.9 kg/m² No current or past diagnosis of eating disorders No major psychiatric disorder Ability to provide informed consent

Exclusion Criteria:

Pregnancy or breastfeeding Severe medical comorbidities affecting metabolic or central nervous system function (e.g., uncontrolled endocrine, hepatic, renal, or cardiovascular diseases) Current psychosis or acute suicidality Current serious non-suicidal self-injury Substance dependence Use of medications that substantially alter metabolic or endocrine function (including high-dose systemic corticosteroids, hormonal contraceptives, or psychotropic medications such as antidepressants, antipsychotics, mood stabilizers, or anxiolytics) Positive status for HIV, hepatitis B (HBV), or hepatitis C (HCV) Intellectual disability impairing the ability to provide informed consent Insufficient proficiency in the study language

Participants will be recruited from outpatient psychiatric practices specializing in eating disorders in Zurich, Switzerland. Individuals with anorexia nervosa will be identified by treating clinicians at participating sites, while healthy control participants will be recruited through the same clinical networks and local community outreach.

Individual participant data (IPD) will not be shared due to the sensitive nature of the data and the small sample size, which may increase the risk of re-identification. Data use is restricted to the scope of the approved study protocol and informed consent, and access is limited to authorized study personnel.