MON-339 Secondary Hyperparathyroidism Due to Decrease 1 Alpha Hydroxylase Activity

•Our patient is a 63-year-old African American female with medical history significant for hypertension, class 1 obesity, osteoarthritis of knees who initially presented to the adult ambulatory clinic on 9/19/2013 with complaints of body aches and bone pain. Labs were remarkable for a serum calcium level of 9.8 mg/dl, serum phosphorous of 4.7 mg/dl, and serum parathyroid hormone level of 166 pg/ml (15-65 pg/ml), normal GFR and serum vitamin 25-OH D of 62. A DEXA scan was performed which showed mild osteopenia wof 1.0 (0.8-1.8), serum 1,25 - OH vitamin D of <8 pg/ml, normal alpha and beta carotene level, negative endomysial antibodies and normal magnesium level. A diagnosis of secondary hyperparathyroidism with unclear etiology was made. Same treatment was continued and a follow up in 3 months with repeat labs was advised. Repeat PTH went up to 281pg/ml but serum calcium and phosphate remained normal. Based on normal serum 25 OH vitamin D and low 1, 25 OH vitamin D, patient was started on calcitriol 0.25 mg daily. On next follow up in 3 months PTH decreased to 203pg/ml and 1, 25 OH vitamin D level normalized (35pg/ml). MEN was excluded with normal serum free metanephrine and gastrin levels. On subsequent visits DEXA scan normalized and PTH further trended downward to 101.7 pg/ml. Patient was discharged from endocrine clinic back to the PCP. • •Patient continued to follow up in adult medicine clinic but calcitriol fall off of patient’s medication list likely due to an error. Patient was off of calcitriol for 6 months but continue to take calcium vitamin D.PTH trended up to 186pg/ml and then to 350pg/ml. A referral to endocrinology was made again and a parathyroid sestamibi scan was obtained which did not reveal any abnormal uptake. Serum calcium, phosphate, magnesium and vitamin OH 25 vitamin D remained normal. •Patient was started back on calcitriol 0.5 mg daily and PTH again started to trend downward. The last PTH was down to 82 on March 20th 2019 with normal serum calcium, phosphate, magnesium and eGFR. The final diagnosis was secondary hyperparathyroidism due to decrease 1 alpha hydroxylase activityith a T score of −1.5 at left forearm. A diagnosis of primary hyperparathyroidism was made by the PCP and patient was started on calcium vitamin D and Fosamax and was referred to endocrinology for further evaluation. • •Further testing in the endocrine clinic revealed 24-hour urine calcium of 49 mg (100-300) and urine creatinine. This case report concludes that low 1-alpha hydroxylase activity should be considered as a cause of secondary hyperparathyroidism in a patient with normal GFR and 25-OH vitamin D level