Prophylactic thyroidectomy for MEN 2-related medullary thyroid carcinoma based on predictive testing for RET proto-oncogene mutation and basal serum calcitonin in China.

INTRODUCTION: Early and normative surgery is the only curative method for multiple endocrine neoplasia type 2 (MEN 2)-related medullary thyroid carcinoma (MTC). AIMS: To study the timing of prophylactic total thyroidectomy (TT) for MEN 2-related MTC with different RET mutations in a Chinese population, and to compare the sensitivity and accuracy of fully-automated chemiluminescence immunoassay (FACLIA) and radioimmunoassay (RIA) for serum calcitonin (Ct). METHODS: We collected 24 asymptomatic individuals from 8 unrelated Chinese families with MEN 2, and analyzed RET mutation and Ct levels. Then we performed TT on 17 of the 24 individuals, including TT (2/17), TT with bilateral level VI lymph-node dissection (B-LND(VI); 12/17) and TT with B-LND(VI) + modified unilateral/bilateral/local neck dissection (3/17). RESULTS: Histopathology revealed bilateral/unilateral MTC in 15/17 (88.2%; median diameter, 1.0 cm) and bilateral C-cell hyperplasia in 2/17 (11.8%; p.V292M/R67H/R982C and p.C618Y). Lymph-node metastasis/fibro-adipose tissue invasion (p.C634R) or solely fibro-adipose tissue invasion (p.C634Y) were found in 2/17 (11.8%). Elevated pre-surgical Ct (pre-Ct) was identified by FACLIA in 17/17 (median age, 24.0), while pre-Ct by RIA was found in only 6/15 (P < 0.001). The median follow-up was 22.0 months, during which 16/17 had no abnormality (one p.C634R individual had elevated Ct), and another 7 carriers still had consistently undetectable Ct by FACLIA. CONCLUSIONS: Our study highlights the importance and feasibility of individualized prophylactic TT for MEN 2-related MTC, based on predictive integrated screening of RET and pre-Ct levels. Besides, we recommend FACLIA to measure Ct for earlier diagnosis, treatment and follow-up monitoring of MTC.

Case report: a p.C618S RET proto-oncogene germline mutation in a large Chinese pedigree with familial medullary thyroid carcinoma.

We report a Chinese pedigree with familial medullary thyroid carcinoma. Direct sequencing of the entire coding sequences of Rearranged during Transfection (RET) identified a recurrent c.T1852A (p.C618S) mutation in 13 of 23 members. The polymorphisms c.A135G (p.A45A), c.A1296G (p.A432A), c.T2307G (p.L769L) and IVS19 + 15T > C were also found in 13 carriers, and c.G2073A (p.G691S) was found in 1 carrier. Of the 13 carriers, seven (mean age: 42.6 years, range: 27-64) presented MTC as the isolated clinical phenotype, with elevated basal serum calcitonin (average: 1077.9 ng/L, range: 504-2,652) and a mean diameter of thyroid nodules of 2.97 cm (range: 1.6-4.3); they underwent a total thyroidectomy with modified bilateral/unilateral neck dissection and/or level VI lymph node dissection. The other 6 carriers did not accept surgery (4 rejected, 2 awaited). These were 2 older patients (63 and 32 years) with elevated calcitonin (1359 and 41.4 ng/L) and multi-centric hypoechoic nodules (1.5 and 0.6 cm) with calcifications in both/left thyroid lobes; and Doppler ultrasound showed normal bilateral thyroids in 4 younger carriers (median age: 8.3 years, range: 4-12) but with increased calcitonin (average: 9.7 ng/L, range: 7.87-12.2) in 3 of them. The phenotype here is consistent with the clinical symptoms reported worldwide. We recommend that screening of hotspot regions of RET should be preferentially carried out, while whole-exon sequencing should be performed when clinical signs fail to reveal hotspot mutations or different phenotype discrepancies. Moreover, we strongly suggest prophylactic thyroidectomy should be performed before age 5 in carriers with p.C618S to prevent the occurrence and metastasis of MTC.

The metabolism of glutamine by the preimplantation sheep conceptus and its interaction with glucose.

The metabolism of glutamine and glucose, separately and in combination, by the sheep conceptus recovered on Days 2, 6, 13, 15, 17, and 19 of pregnancy was assessed over 2.5 h. At Day 2, the production of CO2 from glutamine was similar to that from glucose, with additive effects seen when both substrates were present. Between Day 2 and Day 6, there was a three-fold increase in glucose oxidation but no change in the oxidation of glutamine. From Day 13 to Day 19, the oxidation of glutamine was relatively high in embryonic tissue, low in trophoblastic tissue and intermediate in the yolk sac but in all tissues decreased as development progressed. Over this latter period the oxidation of glutamine was reduced to approximately 50% by the addition of glucose to the medium but glucose oxidation was unaffected by the addition of glutamine. At the early stages of development, the incorporation of substrate carbon from glutamine was less than that from glucose but in each case, incorporation into the acid-insoluble macromolecular fraction increased 2-3 times between Day 2 and Day 6. Incorporation of glutamine into the Day-17 and Day-19 conceptus was also measured; embryonic tissue exhibited the highest rate of incorporation and trophoblastic tissue the lowest. Incorporation was lower on Day 19 than on Day 17 and the proportion of carbon isolated in the acid-insoluble fraction represented 20% of the total incorporated. At no time did the addition of glucose to the medium alter incorporation of glutamine into either embryonic tissue or extraembryonic membranes.

Glycolysis and glucose oxidation by the sheep conceptus at different oxygen concentrations.

The effect of changes in oxygen concentration on the catabolic utilization of glucose by the sheep conceptus at selected periods between Days 3 and 19 of preimplantation development was examined by estimating the production of CO2 and lactate from [U-14C]glucose during a 2.5-h culture in vitro in the presence of 20%, 5% and 1% O2. In general, lowering O2 significantly altered the catabolism of glucose with a changing pattern of response depending on the stage at which the conceptus was explanted. For embryos at Days 3 and 6 post insemination, reduced O2 caused no significant change in oxidative utilization of glucose and a small decrease in conversion of the substrate to lactate. By contrast, lowering O2 concentration during incubation of the structures of the advanced conceptus from Day 13 through to Day 19 of pregnancy significantly restrained oxidative utilization of glucose but stimulated its conversion to lactate. The effects of these changing levels of O2 on the generation of energy from glucose in the form of ATP was estimated. Except for the Day-13 conceptus, reduction in O2 concentration had little influence on the calculated amount of ATP produced from glucose, with glycolysis making up the deficit in energy production when reduced O2 inhibits oxidation of the substrate at the later stages of development. At Day 13, the switch in the metabolism of glucose to glycolysis is not fully effective and energy production fell as O2 concentration was reduced. The results indicate a major shift towards dependence by the preimplantation sheep conceptus on the glycolytic pathway for energy generation from glucose as development progresses. This move to glycolysis is increased by low O2 concentration. As a low concentration of O2 most probably exists in the lumen of the sheep uterus, the results indicate that, in utero, the energy required for the rapid growth of the conceptus depends progressively more on glycolysis than oxidative metabolism of glucose. The finding that the Day-13 conceptus has not fully adapted to this method of ATP generation at low O2 concentrations may make it especially vulnerable during development in utero.

Metabolism of glucose by vesicles derived from sheep trophoblast and embryonic discs.

Samples of trophoblast recovered from the sheep conceptus on Day 13 of pregnancy formed spherical vesicles during culture in medium 199. These continued to expand and increase in dry weight over the next 6 days in vitro. After 6 days' culture, the metabolism of glucose by these vesicles was compared with that of Day-13 and Day-19 fresh trophoblastic tissue. The production of CO2 and lactate by vesicles was similar, although not identical, to production by Day-13 fresh tissue and did not exhibit the marked decrease in glucose catabolism seen in Day-19 trophoblast. The tissue from vesicles reacted to reduction in oxygen tension in a manner similar to the reaction of fresh tissue, with decreased glucose oxidation and increased glycolysis. The activity of the pentose phosphate pathway in vesicles was higher, and the activity in Day-19 fresh tissue was much lower, than that in Day-13 fresh trophoblast. Incorporation of glucose into the intracellular biochemical pools by vesicles was similar to incorporation into Day-13 fresh tissue. Limited observations were also made with vesicles derived from embryonic disc. Production of CO2 by these vesicles was intermediate between that detected in fresh Day-13 and Day-19 embryonic tissue. There were not significant differences in lactate production between fresh and cultured samples of embryonic tissue. These results show that vesicles formed in vitro remain metabolically active but do not mimic the biochemical changes seen in the tissue during development in vivo.