Three Patients with Lithium-Associated Hyperparathyroidism: Literature Review Regarding Medical and Surgical Management

Is there a consensus between clinical practice guidelines for conventional and molecular nuclear medicine studies in parathyroid pathology?

Hyperparathyroidism is a common calcium metabolic disorder, characterized by the presence of high concentrations or inappropriately normal concentrations of parathyroid hormone (PTH) in the context of high calcium. Pharmacological and surgical management is available as treatment. The objective of diagnostic imaging is to determine the location of the causal lesion. For these purposes, non-invasive methods can be divided into anatomical or functional studies, with nuclear medicine studies being in the latter category. The objective of this review, is to establish the similarities and differences that exist in the clinical practice guidelines on conventional and molecular nuclear medicine studies in parathyroid disease.

Lithium-associated hyperparathyroidism

Lithium is a mood stabiliser widely used in the treatment and prophylaxis of mania, bipolar disorders and recurrent depression. Treatment with lithium can give rise to various endocrine and metabolic abnormalities, including thyroid dysfunction, nephrogenic diabetes insipidus and hypercalcaemia. Lithium may induce hypercalcaemia through both acute and chronic effects. The initial acute effects are potentially reversible and occur as a result of lithium's action on the calcium-sensing receptor pathway and glycogen synthase kinase 3, giving rise to a biochemical picture similar to that seen in familial hypocalciuric hypercalcaemia. In the long term, chronic lithium therapy leads to permanent changes within the parathyroid glands by either unmasking hyperparathyroidism in patients with a subclinical parathyroid adenoma or possibly by initiating multiglandular hyperparathyroidism. The latter biochemical picture is identical to that of primary hyperparathyroidism. Lithium-associated hyperparathyroidism, especially in patients on chronic lithium therapy, is associated with increased morbidity. Hence, regular monitoring of calcium levels in patients on lithium therapy is of paramount importance as early recognition of lithium-associated hyperparathyroidism can improve outcomes. This review focuses on the definition, pathophysiology, presentation, investigations and management of lithium-associated hyperparathyroidism.