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The current work has been performed by the Cooperative French Group of Medullary Thyroid Carcinoma (GETC). A systematic evaluation of RIA somatostatin (SRIH) was performed in 34 medullary thyroid carcinomas (MTC) (25 inherited, seven sporadic). Plasma SRIH was measured by radioimmunoassay in parallel with calcitonin (CT) and carcinoembryonic antigen (CEA). Immunoassayable SRIH was tested in fresh tumoral tissue samples from the same 34 MTC and, for comparison, in 10 nontumoral thyroid extracts (less than 6 pmol/g wet). Although plasma SRIH was only slightly elevated in two of 20 cases, tumoral SRIH was elevated in 70.6% of our MTC (10 to 3973 pmol/g). The chromatography of two tumoral extracts showed that somatostatin 14 was the major molecular form. We found no correlation (P greater than 0.1) between tumoral SRIH and the following: (1) tumor size (r = 0.227); (2) epidemiologic form of MTC (r = 0.144); (3) plasma SRIH (r = 0.045), plasma CT (R = 0.095) or (4) plasma CEA (r = 0.032). Thus, in the authors' experience, SRIH appears as a major product of tumoral C-cell in human MTC, even when plasma SRIH is normal and SRIH immunohistochemical staining is scarce. Multiple hormonal production of these tumors may explain its presence but SRIH may act also as a regulator, since negative influence of SRIH on CT is demonstrated in normal as well in tumoral conditions.

Seventeen patients with medullary thyroid carcinoma (MTC) underwent venous catheterization (VC) for sampling and serum calcitonin (CT) assay. The VC was performed either after an initial treatment in order to detect cervical recurrences and metastases (16 patients) or to prove abnormal CT thyroid secretion before any treatment (one patient). In 16 of the 32 tumoral localizations suspected by VC (50%), a tumoral focus was proven. For selective/peripheral CT gradient value superior to 2.50, 12 localizations of 12 (100%) were proven and for CT gradient value between 1.50 and 2.50, four localizations of 15 (26.6%) were proven. In six patients with exclusive cervical MTC secreting sites, treatment induced a total remission in two cases (12%) and improved in four cases (23%). The authors conclude that VC has a real value to localize MTC secreting sites. A total remission or an improvement can be obtained after treatment when VC detects exclusive cervical tumors.