Thyroid follicular cancers are one of the thyroid gland cancers. This cancer can lead to metastases to various areas of the body. We describe a patient with thyroid follicular carcinoma who after total thyroidectomy had severe hypercalcemia, increased creatinine, and thyrotoxicosis due to extensive bone metastases. The patient was a 52-year-old man who had femoral neck fracture as the first manifestation of thyroid cancer. He was hospitalized for some time after orthopedic measures because of thyrotoxicosis and deep-venous thrombosis. The study found that the origin of metastatic lesions was thyroid follicular cancer, leading to extensive bone metastases. After administering of methimazole and control of thyrotoxicosis, he was subjected to total thyroidectomy. Methimazole was discontinued immediately after surgery. One month after surgery, ultrasound confirmed that the thyroid was completely removed. However, T3 (triiodothyronine) remained high; besides the patient had hypercalcemia and increased creatinine due to dehydration. The patient was retreated with methimazole due to thyrotoxicosis, and for hypercalcemia fluid therapy, intravenous zoledronic acid was prescribed. These measures led to the normalization of creatinine and glomerular filtration rate. The purpose of introducing this case report was that these symptoms are a rare manifestation of functional metastases of follicular thyroid carcinoma after total thyroidectomy. Bone metastases of follicular thyroid carcinoma may be functional and are lytic that can lead to hypercalcemia and its complications.
Keywords: Follicular thyroid carcinoma; T3-thyrotoxicosis; functional thyroid carcinoma; hypercalcemia; hyperthyroidism; metastases.