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).