Endocrine Abstracts

Introduction: Poorly differentiated thyroid cancers are usually aggressive tumors that lack many of the characteristics of differentiated thyroid tissue, including the ability to uptake and process iodine.

Case report: A 75-year-old male presented with weight loss, tiredness, asthenia, tremor, increased perspiration, tachycardia and bone pain in several locations. A hard and fixed thyroid nodule was palpable in the left lobe (FNA-«follicular tumor»). Laboratory and Imaging workup showed: TSH<0.004 μUI/ml, fT₃=7.3 pg/ml (1.8–4.2), fT₄=1.6 ng/dl (0.8–1.9); thoracic and abdominal CT scan: nodule in the left lobe of thyroid gland with 57 mm; lytic lesion on right clavicle; multiples pulmonary nodules. The patient was treated with methimazole and then underwent total thyroidectomy. The pathology examination revealed a poorly differentiated thyroid carcinoma. A ¹³¹I therapeutic activity of 108 mCi was administered. Post-therapeutic whole body scan showed metastatic lymph node involvement in the mediastinum, lung uptake and bone metastatic lesions in the basis of the skull, right orbit, several rib bones, left scapula, T10 and T11 vertebrae, right humerus, left iliac bone and left femur; some of these lesions did not have iodine uptake. Thyroglobulin=158 028 ng/ml (undetectable Tg-Abs). Head CT showed a supra-sellar mass with sellar invasion. Prolactin=82 ng/ml (n<20), basal/stimulated cortisol=8/17 μg/dl. After surgery, treatment with L-T₄ was started (100 μg/day); this dose was progressively decreased to 12.5 μg/day, as the patient developed atrial fibrillation along with persistently high fT₃ levels. The patient died from pneumonia 4 months after surgery.

Conclusions: This case illustrates two rare clinical manifestations of thyroid cancer: hyperthyroidism (functioning metastasis) and secondary adrenal insufficiency. Despite being considered as a poorly differentiated tumor and having an aggressive behavior, some metastasis seem to preserve the ability to produce/convert T₃.