Painless thyroiditis complicating with hypercalcemic encephalopathy.

Background: Severe hypercalcemia has rarely been reported in patients with hyperthyroidism. Although the pathogenesis is not clear; it is believed to be due to activation of osteoclasts resulting in excessive bone resorption.
Objective: To recognize the unusual cause of hypercalcemia from painless thyroiditis, which could manifest with transient hyperthyroidism in the early stage.
Case Report: A 70-year-old woman presented with watery diarrhea, nausea and vomiting and significant weight loss for two months. Initially, she was misdiagnosed as having Graves'disease from her clinical presentation and thyroid function tests. Oral propylthiouracil was given to treat hyperthyroidism. However two weeks after discharge, she developed altered consciousness due to severe hypercalcemia. After combined treatment of hypercalcemia and severe hyperthyroidism, her symptoms resolved quickly. Later on, her thyroid function tests switched to subclinical hypothyroid at two months after initial presentation. No concurrent pathological conditions could be found to explain the other causes of hypercalcemia. Therefore, painless thyroiditis complicated with severe hypercalcemia was subsequently diagnosed based on her clinical course.
Conclusion: Hypercalcemic encephalopathy is an uncommon manifestation of hyperthyroidism that should be kept in mind in patients who demonstrated clinical pictures of hyperthyroidism and alteration of consciousness. Moreover the present case emphasizes the consideration of painless thyroiditis as a differential diagnosis of hyperthyroidism because anti-thyroid medications were not indicated in this condition.