What laboratory test should be monitored in patients undergoing long-term lithium therapy?

Monitoring thyroid-stimulating hormone (TSH) levels in patients undergoing long-term lithium therapy is essential because lithium can affect thyroid function. Patients on lithium are at an increased risk of developing hypothyroidism due to the drug's impact on the thyroid gland. Regular monitoring of TSH allows healthcare providers to detect any thyroid dysfunction early, facilitating timely intervention. This is particularly important given that hypothyroidism can lead to various metabolic and psychiatric issues.

While several other laboratory tests are important in the management of patients on lithium—such as monitoring renal function to assess creatinine levels, electrolyte balance, and thyroid hormones—TSH specifically addresses the risk of hypothyroidism associated with lithium use. Ensuring the thyroid remains functional is crucial for the overall health of patients being treated with this medication.