Endocrine Abstracts

Introduction: Post-surgical hypoparathyroidism (PSHP) is a frequent complication following ENT surgery. Some patients with head/neck cancers require enteral nutrition (EN) due to dysphagia, mucositis after radiotherapy or chemotherapy, or post-surgical anatomical complications. Formulas of calcitriol are not suitable to be administered via enteral feeding tubes, and side effects of systemic antineoplastic treatment (nausea, vomiting) make calcium and phosphate serum levels difficult to maintain in the presence of PSHP.

Case report: We present the case of a 44–year–old male with a squamous cell carcinoma of the vocal cord stage IIIB (T3N1M0) treated with radiotherapy and chemotherapy until February 2018. After eight months he presented with local relapse. Total laryngectomy, partial esophagostomy and total thyroidectomy were performed. Due to a laryngo-pharyngeal fistula with multiple failed surgical attempts of closure associating long-term dysphagia, a percutaneous radiologic gastrostomy (PRG) was placed. The Endocrinology department was consulted for management of hypothyroidism and PSHP requiring intravenous calcium supplementation, with the following laboratory results: calcium (corrected) 6 mg/dl (8.5–10.5), phosphate 4.1 mg/dl(2.5–4.5), magnesium 1.8 mg/dl (1.72.6), 25OH-vitamin D 24.8 ng/ml(30–100), iPTH 7.2 pg/ml (15–65), TSH 52.54 uIU/ml (0.38–5.33), FT4 5.4 pg/ml(5.8–16.4). Treatment via PRG was initiated with alfacalcidol 2 µg/ml (Etalpha): 2 µg/24 h; calcium acetate 500 mg–127 mg elemental calcium (Royen):1500 mg/8 h (1143 mg elemental calcium/24 h); magnesium lactate 97.24 mg/24 h; levothyroxine 150 µg/24 h. After 20 days of treatment: calcium 8.2 mg/dl, phosphate 4.1 mg/dl, magnesium 1.7 mg/dl, 25OH-vitamin D 32.7 ng/ml, calciuria 0.11 mg/ mgCr24h, TSH 4.15 uIU/ml, FT4 9.62 pg/ml. After twelve months he received chemotherapy due to local relapse, subsequently presenting with emesis and positive Trousseau sign, calcium 6.9 mg/dl, phosphate 6.2 mg/dl, magnesium 1.5 mg/dl, iPTH 5.6 pg/ml. Symptomatic hypocalcemia was persistent despite intravenous calcium supplementation. Off–label treatment was initiated with teriparatide (Forsteo):20 µg/24 h subcutaneous, initially simultaneous with intravenous calcium. After 15 days: calcium 8.5 mg/dl, phosphate 3.3 mg/dl, magnesium 1.5 mg/dl, which allowed for ceasing intravenous calcium and weaning enteral supply of calcium and vitamin D.

Discussion: Management of PSHP in patients with dysphagia is complex due to the contraindication to administer calcitriol via gastrostomy. Alfacalcidol is an active form of vitamin D with 1-hydroxlation requiring hepatic 25-hydroxilation (PTH-independent), and can be administered via gastrostomy. Despite minimal experience with its use, it was effective in our patient for the management of hypocalcemia until the later appearance of chemotherapy-related emesis. Teriparatide is recombinant human PTH (1–34) currently approved for treatment of osteoporosis in postmenopausal women. However, teriparatide may be used off-label in certain patients with hypoparathyroidism who cannot tolerate oral nor enteral calcium and vitamin D in order to achieve and maintain calcium-phosphate homeostasis.