Few patients with thyroid nodules have high serum calcitonin concentrations indicative of medullary thyroid cancer
(July 2007)
The background of the study. Medullary cancers of the thyroid, a rare type of thyroid cancer, secrete calcitonin, so named because it temporarily lowers serum calcium concentrations. In this study, serum calcitonin was measured in patients with thyroid nodules, and the results in patients who had high values were correlated with the findings in those who underwent surgery.
How the study was done. Basal serum calcitonin was measured in 5817 patients (4706 women, 1111 men) with thyroid nodules. Among them, 4894 patients had one or more thyroid nodules, 436 Hashimoto’s disease and one or more nodules, 276 a functioning thyroid adenoma, and 211 a toxic nodular goiter.
Basal serum calcitonin values (normal,  10 pg/ml) were categorized as follows: 10 pg/ml, negative; >10 to <20 pg/ml, indeterminate;  20 to <100 pg/ml, suspicious; and 100 pg/ml, strongly suspicious for medullary cancer. A pentagastrin stimulation test was done in those with suspicious values; a peak value of >100 pg/ml indicated the presence of medullary cancer. Surgery was recommended for patients with basal or stimulated serum calcitonin values >100 pg/ml and those who had biopsy results suggestive of any type of thyroid cancer.
The results of the study. The basal serum calcitonin values were  10 pg/ml in 5535 of the 5817 patients (95 percent). Among the other 282 patients (5 percent), most had values of >10 to <20 pg/ml (indeterminate).
Surgery was advised for 26 patients on the basis of their serum calcitonin values. All 9 patients who had basal values 100 pg/ml proved to have medullary cancer. Among the 17 patients who had stimulated values >100 pg/ml, 6 had medullary cancer. Overall, 15 patients (0.3 percent) had medullary cancer. None of the 723 patients with normal basal serum calcitonin values who underwent thyroid surgery for other reasons had medullary cancer.
The conclusions of the study. Few patients with thyroid nodules have medullary thyroid cancer. Among them, high basal or pentagastrin-stimulated serum calcitonin values are sensitive and specific indicators of this tumor.
The original article. Costante G, Meringolo D, Durante C, Bianchi D, Nocera M, Tumino S, Crocetti U, Attard M, Maranghi M, Torlontano M, Filetti S. Predictive value of serum calcitonin levels for preoperative diagnosis of medullary thyroid carcinoma in a cohort of 5817 consecutive patients with thyroid nodules. J Clin Endocrinol Metab 2007;92:450-5.
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