Background: Hypoparathyroidism (HypoPT) is characterized by low calcium and parathyroid hormone (PTH), often secondary to thyroid surgery. Treatment consists in activated vitamin D and calcium supplementation. Such treatment may be difficult in patients with malabsorption as calcium usually requires an acid environmental to dissolve, while calcitriol needs an intact intestine for a full absorption.
Case report: A 36-year old woman had a history of sleeve gastrectomy and Single Anastomosis Duodeno-Ileal switch (SADIS). She underwent total thyroidectomy for a papillary thyroid carcinoma. After surgery, she presented paresthesia. PTH was 3.4pg/ml and calcium 6.5 mg/dl. TSH was normal. The patient started calcium carbonate 3 gr and calcitriol 1.5 mg/day without resolution. Oral treatment was increased up to calcium carbonate 9 gr and calcitriol 4 mg/day, with poor control of the disease. The patient refused PTH analogues. For that, intravenous calcitriol 3 mg/week and calcium gluconate 3 gr/week infusion was started, with good control of symptoms. Oral treatment was continued calcium carbonate 3 gr and calcitriol 4 mg/day. After 6 months, calcitriol infusion was interrupted and at present, the patient is on high dose oral treatment. Calcium is 8.5 mg/dl.
Conclusion: In HypoPT the goals of supplementation are preventing symptoms of hypocalcemia, maintaining normal calcium levels, avoiding hypercalcemia and renal calcifications. Patients who have undergone gastric bypass or duodenal resection have an increased risk for hypocalcemia due to malabsorption. If available, calcium citrate or recombinant human PTH (rhPTH) can be considered. Alternatively, intravenous calcium and calcitriol infusion is useful to control the disease. When there is a good control, infusion can be interrupted to start an high dose oral therapy. Even when the patient is stabilized on an oral regimen, episodes of hypocalcemia may occur, so careful monitoring is required.