AACE2021-A-1082: Primary Hyperparathyroidism: A Case Report of Management with Extra Ordinary Low Dose of Cinacalcet in an Elderly Male

Abstract

Primary Hyperparathyroidism is a common cause of Hypercalcemia and is often seen in endocrine clinics. Majority of patients are found to have solitary parathyroid adenomas which may be associated with other endocrine problems. Common systemic complications are secondary osteoporosis, renal stones, pancreatitis and peptic ulcers. Surgery remains the mainstay of treatment for correction of pathology, however patients who do not meet the criteria or in whom surgery is contraindicated are managed conservatively and with calcimimetic agents such as cinacalcet. Case report and literature review. We are reporting a case of a 73 years old male who was referred to the endocrine clinic for work up of hypercalcemia. His past medical history was significant for well controlled Type 2 Diabetes and Hypertension. During his work up, he was found to have elevated serum calcium of 11.7 mg/dl, elevated serum PTH of 767 ng/L and 24 hours urinary calcium excretion of 446 mg/dl. Renal functions and 25 hydroxy vitamin D levels were within normal limits and the ultrasound and DEXA scan were negative for presence of any renal stone or osteoporosis. His two elder brothers also had a history of parathyroidectomy. He was reluctant for surgery and therefore imaging for the neck was also omitted. He was started on cinacalcet 15 mg/ day with an initial presumption of increase in dose requirement afterwards. However his serum calcium levels showed a remarked improvement and within one month they dropped to 9.9 mg/dl. The second subsequent test showed a serum calcium of 8.9 mg/dl after which the dose was reduced to 15 mg every alternate day. A presumption of tumor necrosis was made but the calcium levels rose higher on stopping cinacalcet and again went back to normal on the extra ordinary low dose of 15 mg every alternate day. His 3 years follow up to our clinic on this maintenance dose has shown steady calcium levels, improvements in serum PTH with fluctuations between 260 – 380 ng/L and no subsequent complication. Primary Hyperparathyrodism is a common cause of hypercalcemia which if left untreated can have serious systemic complications. Surgery remains the mainstay of treatment but in patients not meeting the criteria or in whom surgery is contraindicated, medical therapy is an option which includes dietary measures, bisphosphonates and calcimimetics like cinacalcet. The usual dose of cinacalcet is between 30 – 90 mg/day. Our case represents an unusual story of improvement on a very low dose of calcimimetic. More cases need to be evaluated and tested on low dose and may-be we can have a change in the recommendations in future.