I appreciate Dr. McInnis’s article and his recommendation to monitor the comprehensive metabolic profile, including the calcium level, before and during lithium treatment. There is an association among lithium treatment, hypercalcemia, and hyperparathyroidism.1,2 This can occur by lithium reducing parathyroid hormone suppression or stimulating parathyroid glands.3
Surprisingly, many guidelines do not include a recommendation to monitor the calcium level; however, the International Society for Bipolar Disorders and other experts do recommend obtaining a calcium level before initiating lithium therapy and at least annually thereafter.1,4 If hypercalcemia is present, assessing lithium and the parathyroid hormone level is recommended.3
Clinicians can continue lithium and monitor calcium if treatment is beneficial, hypercalcemia is mild, and the patient is asymptomatic.2 For a symptomatic patient or one who has significant hypercalcemia, clinicians should consider discontinuing lithium and monitoring for a normalizing calcium level.2 For patients with significant hypercalcemia who need lithium therapy, consultation with an endocrinologist is advised.3
Jonathan R. Scarff, MD
VA Outpatient Clinic
Spartanburg, South Carolina
Dr. McInnis responds
Generally, calcium is included in the comprehensive biochemistry panel (Table 1). Typically, magnesium or phosphorus is overlooked, and therefore was specifically included in the table of recommendations. There is a complex relationship between lithium and calcium; Dr. Scarff’s points highlight this. It is noteworthy that lithium normalizes the calcium amplitude during action potentials in neurons derived from induced pluripotent stem cells from persons with BD1; this suggests that there might be a direct mode of action in BD involving lithium and calcium. This finding further emphasizes the importance of monitoring calcium, and the wise clinician will verify that it is included in the comprehensive biochemistry panel.