This multi-site, pilot study will assess vitamin D supplementation in children and young adults with Glomerular Disease. .

Vitamin D deficiency has been linked to a variety of adverse health outcomes. Nephrotic patients have very low vitamin D levels, and the underlying mechanisms are not known. Furthermore, approaches to safely and effectively supplement vitamin D in these patients have not been established. The purpose of this research study is to learn if vitamin D supplementation is safe and effective in patients with primary glomerular disease and to also help establish the treatment guidelines. About 35 patients with primary glomerular disease, ages 5-30 years old, will take part in this study. Participants will be asked to take vitamin D supplements each day for 12 weeks and will have 3 study visits.

Inclusion Criteria:

• Males or females, age 5-30 years
• Diagnosis of primary glomerular disease (such as steroid-resistant nephrotic syndrome, minimal change disease, FSGS, membranous nephropathy, membranoprolfierative glomerulonephritis, and Immunoglobulin A [IgA] nephropathy) without systemic inflammatory disorders (i.e. lupus, vasculitis)
• Serum 25(OH)D level <30 ng/ml and urine protein:creatinine ratio ≥0.5 at Screening Visit.

Exclusion Criteria:

• Pregnancy
• estimated Glomerular Filtration Rate (eGFR) <30 ml/min/1.73m2 at Screening Visit
• Serum phosphorus > 5.5 mg/dl or hypercalcemia
• Chronic medical conditions or medications unrelated to the renal disease that may impact vitamin D status
• Known history of kidney stone(s)