Thyroid Hormones in CKD

This is a retrospective, observational, study evaluating circulating thyroid hormone profiles in patients with severe chronic kidney disease (CKD stages G4-G5, non-dialysis). The study includes one cohort of patients with non-ADPKD CKD and a second including a matched subset of patients with Autosomal Dominant Polycystic Kidney Disease (ADPKD) at the same CKD stage,. For the non-ADPKD CKD group, serum and urine samples will be retrieved from the certified biobank of the Centro Daccò (Mario Negri IRCCS). For the ADPKD group, analyses will be performed exclusively using existing clinical and laboratory data available within the REORIENTED study database. Laboratory measurements will be performed on stored biological samples from the non-ADPKD CKD group to assess thyroid hormones (rT3, fT3, tT3, fT4, tT4, and TSH). Clinical and laboratory data for both cohorts will be obtained from the respective study databases and linked within a predefined temporal window relative to sample collection (where applicable).

Inclusion criteria * Non-ADPKD CKD * CKD stage G4, included in the ADAPT study * Availability of stored serum and urine samples in the biobank suitable for thyroid hormone analysis * Availability of relevant clinical and laboratory data within a predefined time window from sample collection * Signed informed consent for storage and future research use of biological samples and clinical data * ADPKD CKD * CKD stage G4, included in the REORIENTED study * Availability of complete thyroid hormone profile and relevant clinical data Exclusion criteria (applied to both groups as far as possible) * Known history of thyroid disease (hypothyroidism, hyperthyroidism, thyroiditis, or thyroid cancer) * Treatment with thyroid hormone replacement or antithyroid drugs * Use of medications known to interfere with thyroid function (e.g., amiodarone, lithium, interferon) * Systemic corticosteroid or immunosuppressive therapy at the time of sampling (if data available) * Dialysis treatment or history of kidney transplantation at the time of sampling * Acute illness, infection, or hospitalization close to the time of sample collection (if identifiable)