European Reference Networks (ERNs) aim to improve access to specialised healthcare and expertise for patients with rare and complex diseases. Within endocrinology, the European Reference Network on Rare Endocrine Conditions (Endo-ERN) brings together expert centres across Europe. Understanding clinical activities and patient numbers across the network is essential for defining future network requirements and improving care pathways.

To provide an overview of clinical activities within Endo-ERN and to evaluate the distribution of rare endocrine conditions managed across the network, with the aim of supporting alignment of future network criteria and quality indicators.

Clinical activity data from Endo-ERN reference centres were collected and analysed across the different Main Thematic Groups (MTGs) covering rare endocrine conditions. Data sources included information provided by participating centres and electronic reporting through the European Registries for Rare Endocrine Conditions (EuRRECa) platform, including the electronic reporting system (e-REC).

The analysis demonstrated substantial variation in the number and type of rare endocrine conditions managed across Endo-ERN expert centres. Differences were observed between centres and thematic groups regarding patient volumes, disease categories, and clinical activities. The findings highlighted the need for harmonised definitions of clinical activity and common criteria to support monitoring and evaluation of expert centres within the network.

This overview of clinical activities within Endo-ERN provides important insights into the organisation and delivery of care for rare endocrine conditions across Europe. Standardised approaches for measuring clinical activity are needed to support continuous monitoring, improve collaboration between expert centres, and strengthen future development of European Reference Networks.

Reliable information on clinical activities is essential for evaluating and improving rare disease networks. The collaboration between Endo-ERN and EuRRECa, including the use of electronic reporting through e-REC, provides a foundation for monitoring rare endocrine conditions and supporting quality improvement initiatives across Europe.