Wimalawansa S J
Department of Medicine (Endocrinology), Royal Postgraduate Medical School, London, England.
J Bone Miner Res. 1993 Apr;8(4):467-73. doi: 10.1002/jbmr.5650080411.
The quantitative analysis of immunoreactive calcitonin (iCT) is the assay of choice for diagnosis and follow-up of patients with medullary thyroid carcinoma (MTC). However, in a small percentage of patients with MTC or C cell hyperplasia (CCH), basal and stimulated iCT levels may not be significantly elevated. In these patients, calcitonin gene-related peptide (CGRP) radioreceptor assay (RRA) can be used complementary to immunoassay for CT (or katacalcin) for prompt diagnosis of MTC and CCH. CGRP RRA is a robust, rapid, sensitive, and specific determinant of "receptor-recognized" CGRP (RR-CGRP; intact molecule of CGRP) either in plasma or in tissue extracts. Plasma RR-CGRP levels rose > 100% 2-5 minutes after stimulation with intravenous pentagastrin (calcium or oral alcohol) (p < 0.001), whereas iCGRP levels were raised to a lesser degree (p < 0.01). In six patients who had a false positive iCT response after pentagastrin or had raised basal iCT levels measured with a two-site immunoradiometric assay, RR-CGRP showed only a minimal change. On the other hand, in patients with CCH (true positive, n = 8), iCT was increased by only 40% after pentagastrin but RR-CGRP levels rose by 140% (p < 0.001). No change in iCT or RR-CGRP levels in plasma were detected in healthy normal volunteers after administration of pentagastrin. Therefore, in addition to the plasma iCT levels, RR-CGRP would resolve some of the difficult diagnostic problems associated with MTC and likely improve the specificity and sensitivity of identifying CCH.
免疫反应性降钙素（iCT）的定量分析是甲状腺髓样癌（MTC）患者诊断和随访的首选检测方法。然而，在一小部分MTC或C细胞增生（CCH）患者中，基础和刺激后的iCT水平可能不会显著升高。在这些患者中，降钙素基因相关肽（CGRP）放射受体分析（RRA）可作为CT（或降钙素原）免疫分析的补充方法，用于MTC和CCH的快速诊断。CGRP RRA是血浆或组织提取物中“受体识别”的CGRP（RR-CGRP；CGRP完整分子）的一种可靠、快速、灵敏且特异的检测方法。静脉注射五肽胃泌素（钙或口服酒精）刺激后2-5分钟，血浆RR-CGRP水平升高>100%（p<0.001），而iCGRP水平升高程度较小（p<0.01）。在6例五肽胃泌素刺激后iCT反应假阳性或采用双位点免疫放射分析测得基础iCT水平升高的患者中，RR-CGRP仅显示微小变化。另一方面，在CCH患者（真阳性，n = 8）中，五肽胃泌素刺激后iCT仅升高40%，但RR-CGRP水平升高140%（p<0.001）。给予五肽胃泌素后，健康正常志愿者血浆中的iCT或RR-CGRP水平未检测到变化。因此，除了血浆iCT水平外，RR-CGRP将解决一些与MTC相关的诊断难题，并可能提高识别CCH的特异性和敏感性。
