Endocrine Abstracts

Procalcitonin (PCT) is a sepsis diagnostic marker and mortality predictor, although its elevation can be related to other diseases such as medullary thyroid carcinoma (MTC). A 72-year-old woman was transferred to the intensive care unit of our institution from another center. One week before, she had been admitted with a clinical picture of progressive malaise, fever, and dyspnea. Weeks before her admission, she had consulted for dyspnea, anorexia, asthenia, and weight loss. Initial studies revealed bilateral lung infiltrates with leukocytosis and high C-protein reactive (CPR), starting antibiotics after discarding SARS-COV-2 infection. Despite active treatment and support, the clinical condition worsened, with renal and respiratory failure, needing orotracheal intubation. A computerized tomography scan (CT) showed persistent lung infiltrates and a 14 mm nodule in the right lung’s lower lobe. After transferring to our center, she showed leukocytosis, high CPR, and remarkably high PCT (4560 ng/ml). She was treated with meropenem, trimethoprim-sulfamethoxazole, levofloxacin, vancomycin, and caspofungin. CPR levels and leukocytosis improved, but PCT levels did not. Another CT showed persistent lung infiltrates and two nodules in the left thyroid lobe. We determined calcitonin (11.072 pg/ml) and carcinoembryonic antigen (CEA) levels (521.4 ng/ml) and performed a core needle biopsy (CNB) of the thyroid nodules, revealing an MTC. There was no ultrasonographic evidence of cervical nodal disease. The patient’s clinical condition worsened, with no evidence of any infectious foci and sustained PCT levels. A whole-body magnetic resonance imaging (MRI) seven days after admission showed multiple hepatic, osseous, and cerebral metastatic foci. The patient died three days later. The present case reflects an outstanding clinical debut of a metastatic MTC. The first signs of the disease were disproportionately high levels of PCT, mimicking a septic shock. The usual presentation of MTC is the detection of a cervical mass. It can also be detected in family studies after discovering a germinal RET mutation, and exceptionally by clinical symptoms, derived from hormonal hyperproduction, either diarrhea or flush secondary to calcitonin or paraneoplastic (Cushing’s syndrome secondary to ACTH production). In this case, PCT levels were exceptionally high despite intensive sepsis treatment and other sepsis markers improvement. The thyroid nodule evaluation and calcitonin and CEA evaluation reassured the MTC suspicion, confirmed by CNB. Calcitonin levels suggested metastatic spread, not confirmed by CT but established by MRI.