CKiD is an important research study looking at the health of children, teenagers, and young adults who have kidney problems. This research is being done to identify what factors help kidneys stay healthy, and also to see how kidney problems affect health and well-being. Teenagers and young adults 16-22 years old who have been diagnosed with chronic kidney disease (CKD) may be eligible to join the study. The CKiD study has enrolled approximately 1100 children and teenagers across North America since the study began in 2003. Our goal now is to enroll teenagers and young adults in the study. By doing this we can have a better idea of what happens to kidney function and overall health as someone with childhood chronic kidney disease grows up. This will help provide us with a more complete picture of CKD from childhood through adulthood.

Cure Glomerulonephropathy Network (CureGN) is a multi-year study of 2,400 children and adults with four rare glomerular (kidney) diseases at over 50 centers in the US, Canada, and Italy. The purpose of CureGN is to create a patient research network to learn about four major causes of glomerular disease : 1. Minimal Change Disease (MCD) 2. Focal Segmental Glomerulosclerosis (FSGS) 3. Membranous Nephropathy (MN) 4. IgA Nephropathy (IgAN)

The purpose of this NIH-funded placebo-controlled clinical trial is to determine how well ferric citrate will lower FGF23, correct anemia and iron levels in the blood, and maintain normal levels of phosphate in children with CKD. Chronic Kidney Disease (CKD) is a condition in which the kidney function is decreased. Fibroblast Growth Factor 23 (FGF23) is a hormone that regulates blood phosphate levels. High FGF23 levels are linked with worsening of kidney, bone & heart health. Ferric Citrate is an oral medication that decreases the absorption of dietary phosphate by the gut, lowers FGF23 levels and raises iron stores in the body. Ferric Citrate is approved in adults with CKD but has not yet been studied in children.

For more information visit www.fit4kidstudy.com

The purpose of this study is to identify components of a physical activity intervention that are effective and meaningful to teenagers with chronic kidney disease (CKD).

Participants will be assigned to 1 of the 16 study groups and will be asked to wear a Fitbit. Participants will also be given a step count goal, answer questionnaires, and complete hand grip strength assessments.

Participants may also be asked to have one-on-one meetings with an exercise coach.

All visits may be completed remotely.