Liquid chromatography coupled with mass spectrometry (LC-MS/MS) is now the method of choice for steroid hormone analysis, as it enables analyses to be carried out on small-volume samples on a wider range of hormones, with improved specificity compared with immunoassays. Hormone assays currently face a twofold problem: on the one hand, immunoassays are highly dependent on the synthesis of antibody kits manufactured by companies with immunotechnology expertise; on the other hand, these immunoassays may require the use of radioactive products for quantification, generating considerable risks for both staff and environment. There are international recommendations from expert societies (World Anti-Doping Agency, Endocrine society) to develop new, more reliable assay methods, such as LC-MS/MS, and to phase out immuno- and radioassay techniques.

However, changing measurement methods requires the development of reference values to maintain and optimize the management of patients.

The aim of this project is therefore to establish usual values in a paediatric population, through collaboration between the clinical departments of the APHP and the METOMICS laboratory, which has mastered the technology.

This is a prospective, multicentric, non-randomized. The study will be uncontrolled, as it will use subjects considered "healthy" to establish reference values.

Recruitment is planned to take place in hospital consultations at recruiting centers belonging to the AP-HP.

During the blood sample prescribed as part of the follow-up consultation, an additional blood tube will be collected after information, consent and inclusion.

The following acts and procedures will be added as part of the research:

• additional tube, respecting the total volume taken according to weight (maximum volume of 2.7mL);
• Routine circuit for sending and receiving the tube to ensure the relevance of standards established in real life.
• A biological collection will be set up. Pseudonymized data will be collected on a secure REDCap database. The source data will be: Recruiting center; Age; Gender; Pubertal stage if available; Results of blood tests carried out by mass spectrometry as part of this research.

The clinical database will be completed by investigators from the Endocrine Functional Explorations Department at Trousseau Hospital and biologists from the METOMICS Department at Saint-Antoine Hospital. Data will not be processed outside the AP-HP. Data will be kept in an active secured database for the duration of the study and up to 2 years after the last publication, and archived for 15 years.

Mass spectrometry analyses will be carried out under the supervision of Pr Antonin Lamazière, Head of the Clinical Metabolomics Department at Hôpital Saint Antoine. Data from these analyses will be stored in the same clinical laboratory and shared only with/between the principal investigator and the study methodologist.

During the research phase, the collection will be stored at the Clinical Metabolomics Department (METOMICS) laboratory, under the responsibility of Prof. Antonin Lamazière, for 2 years. At the end of the research, the samples will be stored for a maximum of 15 years.

Inclusion Criteria:

• Male or female patient ≤ 20 years old
• undergoing a blood sample as part of their pathology routine follow-up

Exclusion Criteria:

• Any identified or suspected endocrine pathology
• Any acute infectious or inflammatory disorder

Patients followed in paediatrics from birth to 20 years undergoing a blood sample as part of their pathology routine follow-up in one of the identified recruiting centers (see below).

Patients with no identified or suspected endocrine pathology or no infectious or inflammatory disorder.