The Effects of Lithium on Calcium and Parathormone Levels: A Cross-sectional Study with Healthy Controls

Abstract

Objective: Despite lithium associated hyperparathyroidism (LAH) can lead to many complications, little notice has been paid to this side-effect. The aim of this study was to investigate the effects of lithium on calcium and parathyroid hormone levels and the relation between lithium use and thyroid diseases.

Method: This cross-sectional study was carried out with 87 lithium-treated patients and 65 volunteers who had a similar age and gender distribution with the lithium group. Serum levels of corrected calcium, intact parathormone, phosphorus, magnesium, alkaline phosphatase, free thyroxine, thyroid stimulating hormone, thyroid autoantibodies and creatinine were assessed, and also, thyroid and parathyroid ultrasonography was conducted. Further detailed investigations were made depending on the elevation of the initially measured calcium and/ or parathormone levels.

Results: Median values of serum levels of the corrected calcium and the intact parathormone were significantly higher in the lithium group. Calcium levels had a mild correlation with the duration of lithium treatment. In the first assessment, while all control individuals had values within the normal reference range, 11 lithium-treated patients had corrected calcium and/or intact parathormone levels above the normal reference levels. All of the five patients, who were diagnosed with LAH after further investigation, were also diagnosed with a thyroid disorder.

Conclusion: These results demonstrate that lithium treatment has a relationship with calcium and parathormone levels. The 5.7% prevalence of LAH and potential life-threatening conditions associated with LAH necessitates the use of available low-cost methods to monitor blood calcium levels of lithium-treated patients for early diagnosis.