8810 Improvement in bone mineral density in tertiary hyperparathyroidism after renal transplant treated with parathyroidectomy

Abstract Disclosure: M. Zakher: None. 55 year old man with past medical history of end-stage renal disease (ESRD) and alcoholic cirrhosis who underwent simultaneous liver-kidney transplant (SLKT) seven months prior to presentation to endocrinology who was referred for management of hypophosphatemia as low as 1.0 mg/dl. Prior to the transplant, he had hyperphosphatemia and hyperparathyroidism with phosphate and parathyroid hormone (PTH) levels as high as 8.2 mg/dL and 682 pg/mL, respectively. PTH remained elevated at 244 pg/mL and vitamin D was 35 ng/mL the week of the initial endocrinology visit. Initial DXA scan six months after SLKT showed osteoporosis of the lumbar spine, total left proximal femur, and left femoral neck with T-scores of -3.4, -4.9, -5.6, respectively. Alendronate was started three weeks prior to the initial visit. Urine studies confirmed phosphate wasting with urinary phosphate excretion significantly higher than 100 mg/24h, FEPO4 greater than 70%, and TmP/GFR less than 2 mg/dL. Increased urinary excretion of phosphate was consistent with hyperparathyroidism. The extremely low urinary calcium in the setting of normocalcemia and the history of renal transplant suggested a tertiary hyperparathyroidism. Alendronate was discontinued eight months after the initial visit to reduce the risk of post-parathyroidectomy hypocalcemia and post-parathyroidectomy bone remodeling inhibition.One year after the initial visit, the patient had a bilateral neck exploration with total parathyroidectomy and auto transplantation of the parathyroid. Pathology showed hypercellular parathyroid tissue. He was hospitalized one week after surgery for symptomatic hypolcalcemia (calcium 5.8 mg/dL). He was taking one tablet of calcium carbonate three times daily at home instead of three tablets three times daily as prescribed. He was discharged on calcitriol 0.5 mcg once daily, magnesium oxide 800 mg twice daily, calcium carbonate 1 g three times daily, and cholecalciferol 5000 units once daily. He remained on these for eleven months as well as calcitriol for fifteen months with dose adjustments during visits. Calcitriol was discontinued when calcium was found to be 8.9 mg/dL and the patient was asymptomatic. Repeat DXA scan two years after the baseline DXA showed osteoporosis of the left femoral neck with a T score of -2.5. There was a tremendous improvement from the baseline DXA scan from +20% in the total lumbar spine to +170% in the left femoral neck. DXA scan four years after the baseline DXA scan showed osteopenia of the lumbar spine, total left proximal femur, and left femoral neck with T-scores of -1.7, -2.4, -1.9.This is a 55 year old man who underwent SLKT seven months prior to presentation to endocrinology who was referred for management of hypophosphatemia as low as 1.0 mg/dL found with tertiary hyperparathyroidism who underwent a parathyroidectomy that resulted in significant improvement in bone mineral density test. Presentation: 6/2/2024