{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,29]],"date-time":"2026-09-29T21:07:50Z","timestamp":1790716070208,"version":"4.1.0"},"reference-count":16,"publisher":"SMC Media","issue":"3","license":[{"start":{"date-parts":[[2026,2,12]],"date-time":"2026-02-12T00:00:00Z","timestamp":1770854400000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"<jats:p>Medullary thyroid carcinoma (MTC) is a rare neuroendocrine tumour arising from parafollicular C cells, and serum calcitonin remains its most reliable biochemical marker. Procalcitonin (PCT), widely used in the evaluation of bacterial infections, is usually undetectable under non-infectious conditions. Persistent elevation of PCT in the absence of clinical or microbiological evidence of infection is uncommon and may represent an early clue to underlying endocrine malignancy. We report the case of a 48-year-old woman who presented with markedly elevated PCT levels (&gt;20 ng\/ml) detected during routine laboratory testing despite being asymptomatic and having normal inflammatory markers. Extensive infectious work-up was negative, and antibiotic therapy did not reduce PCT levels. Further endocrine evaluation revealed a calcitonin level &gt;2000 ng\/l, elevated carcinoembryonic antigen, and a suspicious thyroid nodule on ultrasonography. Fine-needle aspiration with calcitonin washout confirmed the diagnosis of MTC. The patient underwent total thyroidectomy with central neck dissection, and histopathology demonstrated a 4.5 cm sporadic MTC without nodal metastasis. Postoperative PCT and calcitonin levels declined markedly, supporting their parallel behaviour in relation to disease activity. This case highlights the clinical importance of considering MTC in patients with unexplained hyperprocalcitoninemia and supports the potential role of PCT as an adjunct biomarker in diagnostic evaluation and postoperative monitoring once infection has been excluded.<\/jats:p>","DOI":"10.12890\/2026_006176","type":"journal-article","created":{"date-parts":[[2026,2,16]],"date-time":"2026-02-16T15:21:13Z","timestamp":1771255273000},"source":"Crossref","is-referenced-by-count":1,"title":["Persistent hyperprocalcitoninemia as the initial diagnostic clue to sporadic medullary thyroid carcinoma"],"prefix":"10.12890","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8490-0767","authenticated-orcid":false,"given":"Aysun","family":"\u015eeker","sequence":"first","affiliation":[{"name":"Department of Internal Medicine, Kartal Dr. L\u00fctfi K\u0131rdar City Hospital, Istanbul, Turkey"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"10397","published-online":{"date-parts":[[2026,2,12]]},"reference":[{"key":"10.12890\/2026_006176_ref1","doi-asserted-by":"crossref","unstructured":"Wells SA Jr, Asa SL, Dralle H, Elisei R, Evans DB, Gagel RF, et al. 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Ther Adv Endocrinol Metab 2025;16:20420188251336091. doi: 10.1177\/20420188251336091","DOI":"10.1177\/20420188251336091"},{"key":"10.12890\/2026_006176_ref4","doi-asserted-by":"crossref","unstructured":"Trimboli P, Giovanella L. Procalcitonin as Marker of Recurrent Medullary Thyroid Carcinoma: A Systematic Review and Meta-Analysis. Endocrinol Metab (Seoul) 2018;33:204-210. doi: 10.3803\/EnM.2018.33.2.204","DOI":"10.3803\/EnM.2018.33.2.204"},{"key":"10.12890\/2026_006176_ref5","doi-asserted-by":"crossref","unstructured":"Kaserer K, Scheuba C, Neuhold N, Weinh\u00e4usel A, Haas OA, Vierhapper H, et al. Sporadic versus familial medullary thyroid microcarcinoma: a histopathologic study of 50 consecutive patients. Am J Surg Pathol 2001;25:1245-1251. doi: 10.1097\/00000478-200110000-00004","DOI":"10.1097\/00000478-200110000-00004"},{"key":"10.12890\/2026_006176_ref6","doi-asserted-by":"crossref","unstructured":"Bihan H, Becker KL, Snider RH, Nylen E, Vittaz L, Lauret C, et al. 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Horm Metab Res 2026. doi: 10.1055\/a-2794-3447","DOI":"10.1055\/a-2794-3447"},{"key":"10.12890\/2026_006176_ref12","doi-asserted-by":"crossref","unstructured":"Elisei R, Bottici V, Luchetti F, Di Coscio G, Romei C, Grasso L, et al. Impact of routine measurement of serum calcitonin on the diagnosis and outcome of medullary thyroid cancer: experience in 10,864 patients with nodular thyroid disorders. J Clin Endocrinol Metab 2004;89:163-168. doi: 10.1210\/jc.2003-030550","DOI":"10.1210\/jc.2003-030550"},{"key":"10.12890\/2026_006176_ref13","doi-asserted-by":"crossref","unstructured":"Broecker-Preuss M, Simon D, Fries M, Kornely E, Weber M, Vardarli I, et al. Update on Calcitonin Screening for Medullary Thyroid Carcinoma and the Results of a Retrospective Analysis of 12,984 Patients with Thyroid Nodules. 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