Category: Other - Parathyroid
Objective : Discuss the diagnosis of hyperparathyroidism after Roux-en-Y gastric bypass surgery (RYGB).
Methods : Case report
A 64 year-old female with history of RYGB presented with a parathyroid hormone (PTH) of 209 pg/mL (normal 10-65), a serum Calcium (Ca) of 10 mg/dL (normal 8.5-10.5), a 25 hydroxyvitamin D (25OHD) of 11 ng/mL (normal 20-80) and a 24 hour urine Ca of 43 mg (normal 50-300). She was not taking calcium or vitamin D supplements. Dual energy x-ray absorptiometry (DXA) scan showed no osteoporosis, and she had no symptoms of hypercalcemia. She was diagnosed with secondary hyperparathyroidism (SHPT) due to vitamin D deficiency and she was treated with 50,000 units weekly of ergocalciferol, but had persistently low 25OHD level below 30 ng/mL. Eight months later the dose of ergocalciferol was increased to 50,000 units twice weekly and after 4 months on the higher dose she had a 25OHD of 30 ng/mL, a PTH of 213 pg/mL and a Ca of 10.1 mg/dL. At this time, the possibilities of normocalcemic primary hyperparathyroidism versus Familial Hypocalciuric hypercalcemia was entertained and conservative follow up was planned. She was lost to follow up for some time and when she returned three years later, she had been off supplements for at least 6 months and a 24-hour urinary calcium was still on the low end at 59.5 mg, calcium 9.6 mg/dL, PTH 179 pg/mL, and Vitamin D 30 ng/mL. DXA showed evidence of osteoporosis with a T score of 0.0 at L1-L4, and of -2.7 at the left femoral neck. She was asked to resume supplementation with 1200 mg of calcium daily and 50,000 units of vitamin D twice weekly and four weeks later, her 24-hour urinary Ca was 156 mg, Ca 10.1 mg/dL, PTH 137 pg/dL, and 25OHD 56 ng/mL. This ruled out both FHH and SHPT, and was most suggestive of primary hyperparathyroidism (PHPT). Neck ultrasound showed a right lower mass measuring 2.2 x 1.2 x 1.0 cm and a left lower mass measuring 3.2 x 1.1 x 1.5 cm, and fine needle aspiration was consistent with bilateral parathyroid adenomas. Parathyroidectomy is planned.
Discussion : SHPT is common following gastric bypass due to malabsorption of calcium and/or vitamin D. Additionally, calcium malabsorption can lead to low urinary calcium excretion. These changes can complicate the evaluation of gastric bypass patients who also have PHPT or FHH.
This case highlights the diagnostic dilemma in identifying the etiology of hyperparathyroidism post gastric bypass surgery, and demonstrates the importance of further investigation of elevated PTH in these patients. Additionally, this case demonstrates that adequate supplementation with calcium and vitamin D can help elucidate the diagnosis when the laboratory evaluation is non-diagnostic.
Julie Schommer– Endocrinology Fellow, University of Iowa Hospitals and Clinics, Iowa City, Iowa
Joseph Dillon– Associate Professor, University of Iowa
Amal Shibli-Rahhal– Endocrinology Fellowship Program Director, University of Iowa Carver College of Medicine, Iowa City, Iowa
University of Iowa Hospitals and Clinics
Iowa City, Iowa
University of Iowa
Staff Physician University of Iowa Hospitals and Clinics