Bone mineral density in patients with lithium-associated hyperparathyroidism

Sammanfattning: Background: Lithium is the most effective long-term treatment for bipolar disease. It has, however,been associated with hypercalcemia and hyperparathyroidism. The aim of the study is to research howlithium associated hyperparathyroidism(LHPT)affects bone mineral density. Method: A sub-analysis was performed on an ongoing randomized prospective study evaluating the operation results from parathyroidectomy versus watchful waiting in 22patients with LHPT. The patients were followed-up for 2 years and their blood samples, bone mineral density (BMD) and FRAX assessment were analysed. The data from LHPT patients was also compared to a separate group of patients with primary hyperparathyroidism (PHPT) corresponding in age.Results: In comparing LHPT patients with PHPT apparent differences in the biochemical profile were detected, including elevated values of ionized Ca in PHPT (p=0.001), lower excretion of 24h urinary calcium in LHPT (p=0.003) and significantly higher values of PTH excretion in PHPT. LHPT showed tendencies to having better BMD (p=0.176). At 2-year follow-up of 8 LHPT patients, biochemicalvalues improved, suggesting cure, including lower risks of skeletal fractures. Discussion: The biochemical features in LHPT are distinctive from PHPT. However, each case is unique, and thebiochemicalvariety issimilar to PHPT. Confounding factors include age, sex, renal function and stability of the bipolar condition. Conclusions:The present study illustratesthat LHPT differs biochemically from PHPT. In comparison to PHPT, LHPT patients tend to have reduced BMD and the present study could not confirm the previous postulation that lithium could be protective of the skeleton. In conclusion, casesof LHPT should be assessed individually, since the clinical course is diverse. In patients risking fracture, parathyroidectomy should be considered.