The prevalence of lithium-associated hyperparathyroidism in a large Swedish population attending psychiatric outpatient units.

Objective: This retrospective study determined the prevalence of lithium-associated hyperparathyroidism (LHPT) in 2 geographically defined, equivalent populations in Sweden, with no other selection bias.

Methods: The medical journals of all patients receiving lithium treatment were examined specifically regarding their biochemistry: calcium, parathyroid hormone (PTH), creatinine, and vitamin D. The condition LHPT was defined biochemically. All patient data were noted, and the prevalence of the condition could thereby be calculated.

Results: A total of 423 patients were included (251 women and 172 men; 3:2), treated over a mean of 13.5 years (range, 1-46 years), aged 19 to 92. 77 patients (18%) were identified with LHTP whose median serum calcium was 2.55 mmol/L and PTH was 99 ng/L. A further 21% showed tendencies toward hypercalcemia. Forty-three percent had vitamin D insufficiency. Five patients (approximately 1%) had undergone parathyroidectomy.

Conclusion: The prevalence of LHPT is high and often goes undetected. Vitamin D insufficiency is common as is polypharmacy. Surgery, for unclear reasons, has not been performed extensively, possibly because of limited knowledge of the underlying pathophysiology or surgery's significance. We present standard recommendations on patient management and suggest continual, specific follow-up including the monitoring of calcium, PTH, and vitamin D at least annually. Surgery should be considered with intention to improve psychiatric well-being and provide multiorgan protection.