Primary functional hypothalamic amenorrhoea in the context of feeding and eating disorders or excessive exercise: Insights from non-athletic and elite athletic populations.

Primary amenorrhoea is defined as the absence of menarche by the expected age, with or without delayed pubertal development in adolescents. It may result from anatomical, genetic, endocrine, and functional causes. Among the latter, we propose the term primary functional hypothalamic amenorrhoea (P-FHA) to describe primary amenorrhoea characterised by hypothalamic-pituitary-ovarian axis suppression in the absence of organic disease. P-FHA is frequently associated with low energy availability (LEA), particularly in individuals with feeding and eating disorders (FEDs) or excessive exercise, often within the spectrum of Relative Energy Deficiency in Sport (REDs). Despite its clinical relevance, P-FHA remains under-recognised, with limited dedicated research. This review aims to synthesise clinical studies addressing P-FHA in the context of FEDs or excessive exercise. A systematic literature search was conducted using PubMed, Web of Science, and Scopus. Studies focusing on P-FHA and its association with FEDs, excessive exercise, and REDs were included. Case reports and aggregated studies combining P-FHA and S-FHA were excluded to ensure specificity. Twenty-four studies addressing patients with P-FHA were identified. Available evidence suggests that the reported frequency of functional hypothalamic causes of primary amenorrhoea may have increased over time, although estimates varied substantially across populations and study designs. In patients with FEDs, the prevalence of PA ranged from 2.4% to 14.8%, while athlete cohorts reported frequencies ranging from 7.3% to 53.8%. FEDs and excessive exercise, including REDs-related conditions, emerged as major clinical settings. Data specifically addressing hormonal profiles or body composition in this context remain limited. P-FHA may represent an early clinical manifestation of chronic LEA occurring during a critical developmental window. Early recognition and multidisciplinary management are essential to minimise potential consequences on growth, skeletal health, reproductive function, body composition, and psychological well-being. Further prospective studies are needed to better define its epidemiology, neuroendocrine mechanisms, and optimal management strategies.