Endocrine Abstracts

Background: Lithium-associated hyperparathyroidism (HPT) is an under-recognised side effect of chronic lithium therapy. Cessation of lithium may precipitate relapse of psychiatric illness. Potential treatment with cinacalcet has been described in two case series recently.

Aim: We present two cases of HPT secondary to lithium therapy used for bipolar affective disorder, which were successfully managed with cinacalcet.

Results: Patient 1 is a 64-year-old gentleman with a history of lethargy, nocturia and polyuria who was found to have hypercalcaemia and HPT. Sestamibi/SPECT scans did not detect any parathyroid adenomas but surgical exploration revealed an enlarged right superior parathyroid gland which was excised. Histopathology confirmed a parathyroid adenoma. However, the calcium and parathyroid hormone (PTH) remained consistently elevated after parathyroidectomy and cinacalcet was introduced at a dose of 30 mg once daily. Calcium and PTH levels improved over 15 months. Patient 2 is a 60-year-old gentleman who was investigated for tiredness, polyuria and pathological fractures and found to have hypercalcaemia and HPT as well as nephrocalcinosis and osteoporosis. No definite parathyroid adenomas were identified on Sestamibi/SPECT scans and a trial of cinacalcet (30 mg once daily titrated with biochemical response) was started. This resulted in normalisation of both calcium and PTH levels within 2 years. In both cases, cinacalcet was well tolerated and the patients improved symptomatically with no further complications from their underlying conditions.

Conclusion: Cinacalcet is known to be effective in primary hyperparathyroidism but our observations also support the use of this calcimimetic agent in lithium-induced hyperparathyroidism as a potential alternative to surgery.