Diagnosis of Renal Osteodystrophy in Patients With Reduced Renal Function

This study is evaluating a procedure called bone biopsy to more accurately diagnose a condition called renal osteodystrophy — a type of bone disease that develops in people with severely reduced kidney function — by directly examining bone tissue instead of relying on blood tests alone. **You may be eligible if (kidney disease group)...** - You are 18 or older - Your kidney function is severely reduced (eGFR of 20 mL/min or lower) - Your parathyroid hormone (PTH) level is either below 150 or above 300 pg/mL **You may be eligible if (control group)...** - You are 18 or older - Your kidney function is normal (eGFR 60 mL/min or higher) - You are being evaluated for prostate health with a PSA under 40 **You may NOT be eligible if...** - You have an active cancer - You are allergic to tetracycline antibiotics - You are pregnant - You have a history of kidney disease (for the control group) - You have a known metabolic bone disease or abnormal calcium/PTH levels (for the control group) Talk to your doctor to see if this trial is right for you.