Endocrine and Metabolic Challenges of Long-Term Lithium Therapy: Diagnostic and Management Considerations

Lithium is a key treatment for bipolar disorder but is associated with significant endocrine and metabolic side effects, particularly lithium-induced hyperparathyroidism (LIH). Characterized by hypercalcemia and inappropriately normal or elevated parathyroid hormone (PTH) levels, LIH can lead to skeletal complications such as osteoporosis. Managing this condition is particularly challenging in psychiatric patients due to adherence issues with follow-up care. We describe the case of a 56-year-old Caucasian female patient with bipolar disorder on long-term lithium therapy (16 years), presenting with recurrent hypercalcemia, hyperparathyroidism, and osteoporosis. Symptoms included fatigue, depression, and cognitive difficulties. Laboratory tests confirmed hypercalcemia (2.8 mmol/L), normal PTH (47.5 pg/mL), and vitamin D deficiency (11.8 ng/mL). Imaging identified a parathyroid adenoma and osteoporosis. Parathyroidectomy failed to resolve hypercalcemia, which persisted at 2.6 mmol/L. Lithium discontinuation led to calcium normalization and improved bone density (8.2% increase in lumbar spine measurements). However, follow-up imaging revealed a small epithelial adenoma, raising concerns about further surgical intervention. Management was complicated by poor adherence to follow-up care. This case highlights the complexities of diagnosing and managing LIH, particularly in patients with psychiatric comorbidities. A multidisciplinary approach involving endocrinology and psychiatry is essential to optimize treatment while balancing lithium's therapeutic benefits against its risks. Further research is needed to refine surgical strategies, calcimimetic therapy, and long-term follow-up protocols for effective management.