Endocrine Abstracts

Although not used as first-line, recombinant human parathyroid hormone (rhPTH) has a role in the treatment of chronic hypoparathyroidism especially when the conventional treatment is deemed unsatisfactory. A 48-yr-old female with a history of total thyroidectomy for a benign multinodular goiter and post-operative permanent hypoparathyroidism was referred to us in 2011 due to treatment resistant hypocalcemia requiring intravenous calcium infusions. Her calcium remained mostly in the range of 1.4-2.0 mmol/l. Other than the history of Raynaud’s Syndrome and lactose intolerance, her past medical history was unremarkable. She was on Thyroxine 100 micg daily, alfa-calcidiol 1 micg twice-daily and Calcium Carbonate 1 g four-times-daily. Upon evaluation she was found to have ongoing abdominal symptoms for an extended period due to Celiac disease and gluten removal improved her symptoms and calcium level for a brief period. She was also on long-term antacids which could have contributed to the malabsorption of calcium salts. Her calcium control remained challenging, hence various options were tried including supplementation with vitamin-D3, changing to calcium citrate, a trial of liquid form of alfacalcidol, and switching to calcitriol. Regretfully, over the next few years (2015-2020), she went on to develop bilateral recurrent breast cancer requiring surgery, chemotherapy, radiotherapy, and adjuvant endocrine therapy. Her calcium level varied markedly during this period with recurrent admissions requiring calcium infusions. As the initial whole-body scan was negative, and she was stable without any local recurrence or distant metastasis from the oncological perspective, in 2021 she was started on rhPTH(1-84) with a good response and stability over calcium level at 100 mg daily. Unfortunately, it had to be stopped after 2-years due occurrence of bony-metastasis from progressive breast cancer. Immediately after stopping the rhPTH, she went down on a spiral of multiple hospital admissions with symptomatic hypocalcemia. Currently, she is on alfa-calcidiol 14 micg daily, Vitamin-D3 1000 IU daily, Calcium Carbonate 4 g daily along with Thyroxine 125 micg daily and her calcium remains in the range of 1.75-2.2 mmol/l. Most recently, she was given IM ergocalciferol 300,000 iu injection which seemed to have kept her calcium at 2.23 mmol/l. Due to the concerns over the evidence from pre-clinical studies for the risk of osteosarcoma, safe use of rhPTH is still not established in the presence of bony metastasis. Physicians are reluctant to use PTH therapy although the benefits outweigh the perceived minute risks; hence further research is needed to establish the safety.