SUN-775 All Time Low: A Follow-Up Case Report On Basal Ganglia Calcification From Chronic Hypocalcemia Following Postsurgical Hypoparathyroidism

Abstract Disclosure: L.B. Teh: None. R.L. Alba: None. Filipinos show higher incidence and risk of recurrence for thyroid cancer, gearing recommendations to total thyroidectomy for all nodular goiter suspicious for thyroid carcinoma on biopsy. Post-operatively, some may experience hypoparathyroidism (hypoPT) that could persist for > 12 months. This chronic hypoPT was associated with long-term sequelae such as basal ganglia calcification (Fahr Syndrome), albeit rare, due to hypocalcemia and hyperphosphatemia. A 70-year-old female underwent total thyroidectomy in 2000 and has been lost to follow-up and non-compliant to medications. On 2018 she presented with loss of consciousness and dizziness. Plain Head CT showed extensive symmetric calcifications on basal ganglia, corona radiata, brainstem and cerebellum. Intact PTH 0.51 pg/ml (N 15-65 pg/ml) and serum ionized calcium (SiCa) 0.91 mmol/L (N 1.12-1.32 mmol/L) were both low. She was discharged with CaCO3 5.4g/day, vitamin D 7200iu/day and calcitriol 0.75mcg/day. SiCa was monitored through the years at OPD, but consistently at subnormal levels. In 2022, plain cranial MRI was done, now noting thalamic calcifications. SiCa was 0.89mmol/L. Calcium, vitamin D and calcitriol were adjusted. In 2024, she again presented with loss of consciousness and dizziness, progressing with slurring of speech, weak gag and slowed movements. SiCa was noted at 0.94mmol/L. Repeat cranial MRI showed progression of symmetric mineralization of the basal ganglia, thalami, subcortical white matter and deep cerebellar hemispheres. Guido et al in 2021 showed that the average duration of hypoPT at the time of first head CT was 11 ± 14.4 years. The goals of treatment of hypoPT are directed toward the severity of symptoms, and serum calcium at least the lower half of the normal range. Conventional treatment involves calcium and vitamin D supplementation, which is pivotal in preventing the progression of Fahr syndrome. Latest recommendations state that for chronic hypoPT patients on calcium supplement >2g/day or active vitamin D >2mcg/day, PTH replacement may be beneficial. REPLACE trial in 2013 achieved 50% reduction of daily dose of oral calcium and active vitamin D with rhPTH, while maintaining normocalcemia, in 53% of the treatment group. As of 2022, International Task Force has not fully recommended a PTH replacement regimen due to lack of studies. To date, there are two new drugs on phase 3 trial. Palopegteriparatide and eneboparatide, both long-acting agents, are able to achieve normocalcemia while being independent from conventional therapy, and are well-tolerated. A newer and longer-acting agent, MBX 2109, in 2024 was on Phase 1 trial for tolerance and safety, aiming once-weekly PTH replacement. While Calcium and Vitamin D are the mainstay management in hypoPT, replacing PTH may now be considered in chronic hypocalcemia unresponsive to conventional treatment, aiming to avoid long-term and disabling complications. Presentation: Sunday, July 13, 2025