Linkage of familial euthyroid goiter to the multinodular goiter-1 locus and exclusion of the candidate genes thyroglobulin, thyroperoxidase, and Na+/I- symporter

Thyroid nodule recurrence following lobo-isthmectomy: incidence, patient's characteristics, and risk factors

PURPOSE

This study was aimed at assessing the incidence and timing of thyroid nodules recurrence, defined as appearance of new benign or malignant nodules in contralateral lobe in patients with benign thyroid nodules or thyroid microcarcinoma treated with lobo-isthmectomy. Patient's characteristics and risk factors associated with this phenomenon were also investigated.

METHODS

A retrospective study was performed by evaluating 413 patients undergoing lobo-isthmectomy with a minimum follow-up of 1 year. Clinical characteristics, surgical interventions and complications, histological diagnosis, and thyroid function at last follow-up were collected.

RESULTS

Single or multiple thyroid nodule recurrence equally occurred in 80 patients (23%) with a median time to relapse of ~ 5 years (range 0.3-34.5 years) after lobo-isthmectomy. Recurrence was significantly associated with younger age (< 46 years) and number of pregnancies in women. Development of hypothyroidism was not rare either (~ 10%) and appeared in 3-19 months; a preoperative TSH level > 2.43 mIU/L was associated with the need of l-thyroxin replacement therapy after surgery. The most frequent surgical complication was transient hypoparathyroidism (4.6%), while the rate of permanent hypoparathyroidism significantly increased in patients submitted to completion thyroidectomy (5.3%).

CONCLUSIONS

Thyroid nodules recurrence following lobo-isthmectomy is not a rare event and occurs within 5 years after surgery, more frequently in younger patients with family history of nodular goiter and in women with multiple pregnancies. Pre-surgical TSH levels may predict the development of post-surgical hypothyroidism, possibly improving the management of patients addressed to surgery.

Identification of a KEAP1 germline mutation in a family with multinodular goitre

BACKGROUND

The familial clustering of multinodular goitres (MNGs) with a dominant mode of inheritance has been repeatedly reported. Linkage studies have revealed several genetic loci responsible for familial MNG; however, most of the causative variants remain unknown.

METHODS AND RESULTS

Through linkage analysis using single-nucleotide polymorphism markers, we identified a new MNG locus on 19p13.2-q12 in a five-generation Japanese MNG family. Subsequent mutation searches focusing on the candidate 25-Mb region of chromosome 19 identified a heterozygous mutation, c.879_880delinsA, p.Asp294Thr, fs*23, in exon 3 of the KEAP1, which plays a central role in the cytoprotection pathway against oxidative stress. Reverse transcriptase-PCR analysis showed low expression of wild type KEAP1 accompanied by no transcription product of mutant allele in the normal and goitre region of thyroid tissues obtained from the proband. In agreement with previous studies showing that KEAP1 negatively regulates NFE2L2, the NFE2L2 target genes GSTA4 and GCLC were up-regulated in the thyroid tissues of the patient.

CONCLUSIONS

This study identified the first KEAP1 mutation in MNG. The results provide insights into the pathogenesis of goitre which develops in the organ continuously exposed to oxidative stress during hormone synthesis.

Molecular pathogenesis of nodular goiter

INTRODUCTION

Familial clustering of goiters mostly with an autosomal dominant pattern of inheritance has repeatedly been reported. Moreover, other environmental and etiologic factors are likely to be involved in the development of euthyroid goiter. Therefore, a multifactorial etiology based on complex interactions of both genetic predisposition and the individuals' environment is likely.

METHODS

The line of events from early thyroid hyperplasia to multinodular goiter argues for the predominant neoplastic (i.e., originating from a single mutated cell) character of nodular structures. Etiologically, relevant somatic mutations are known in two thirds of papillary and follicular thyroid carcinomas and hot thyroid nodules. In contrast, the somatic mutations relevant for benign cold or benign isocaptant thyroid nodules which constitute the majority of thyroid nodules are unknown.

RESULTS

The nodular process is triggered by the oxidative nature of thyroid hormone synthesis or additional oxidative stress caused by iodine deficiency or smoking. If the antioxidant defense is not effective, this oxidative stress will cause DNA damage followed by an increase of the spontaneous mutation rate which is a substrate for tumorogenesis.

CONCLUSIONS

Therefore, the hallmark of thyroid physiology--H(2)O(2) production during hormone synthesis--is very likely the ultimate cause for the frequent mutagenesis in the thyroid gland. Because iodine deficiency increases the oxidative burden, DNA damage and mutagenesis could provide the basis for the frequent nodular transformation of endemic goiters.

Genetic Predisposition to Familial Nonmedullary Thyroid Cancer: An Update of Molecular Findings and State-of-the-Art Studies

Familial thyroid cancer has become a well-recognized entity in patients with thyroid cancer originating from follicular cells, that is, nonmedullary thyroid carcinoma. The diagnosis of familial thyroid cancer provides an opportunity for early detection and possible prevention in family members. Understanding the syndromes associated with familial thyroid cancer allows clinicians to evaluate and treat patients for coexisting pathologic conditions. About five percents of patients with well-differentiated thyroid carcinoma have a familial disease. Patients with familial non-medullalry thyroid cancer have more aggressive tumors with increased rates of extrathyroid extension, lymph node metastases, and frequently show the phenomenon of “anticipation” (earlier age at disease onset and increased severity in successive generations). So far, four predisposition loci have been identified in relatively rare extended pedigrees, and association studies have identified multiple predisposing variants for differentiated thyroid cancer. This suggests that there is a high degree of genetic heterogeneity and that the development of this type of tumor is a multifactorial and complex process in which predisposing genetic variants interact with a number of incompletely understood environmental risk factors. Thus, the search for the causative variants is still open and will surely benefit from the new technological approaches that have been developed in recent years.

Evidence for a susceptibility gene (SLEH1) on chromosome 11q14 for systemic lupus erythematosus (SLE) families with hemolytic anemia

Hemolytic anemia is a forme fruste of systemic lupus erythematosus (SLE), being observed months or even years before the onset of other clinical manifestations in some patients. We hypothesized that hemolytic anemia in those SLE-affected patients would identify a group of SLE pedigrees that share a high degree of genetic homogeneity. From 160 multiplex SLE pedigrees, we sought evidence for linkage in 35 (16 African-American, 17 European-American, and 2 Hispanic) who had at least one SLE-affected patient with hemolytic anemia. Significant linkage was present at 11q14 in the 16 African-American pedigrees, yielding a maximum two-point logarithm of odds (LOD) score of 4.5 at D11S2002. The segregation pattern of SLE in these African-American pedigrees suggested a dominant mode of inheritance and, when maximized across penetrance and disease allele frequencies, produced a multipoint LOD of 4.7. Multipoint analysis yielded a multipoint heterogeneity LOD score of 3.6 (alpha = 0.63), again with maximum LOD at D11S2002. Finally, markers typed 7 centimorgans to either side of D11S2002 achieved LOD scores of 3 or better by using the maximized model, supporting linkage to 11q14. Clearly, pedigree ascertainment based on select clinical manifestations is an important tool, capable of revealing otherwise cryptic genetic linkages in complex genetic diseases. Thus, we show strong evidence for an SLE susceptibility gene, SLEH1, near D11S2002 in African-American pedigrees multiplex for SLE that have at least one SLE-affected patient with hemolytic anemia.

Localization of a susceptibility gene for familial nonmedullary thyroid carcinoma to chromosome 2q21

The familial form of nonmedullary thyroid carcinoma (NMTC) is a complex genetic disorder characterized by multifocal neoplasia and a higher degree of aggressiveness than its sporadic counterpart. In a large Tasmanian pedigree (Tas1) with recurrence of papillary thyroid carcinoma (PTC), the most common form of NMTC, an extensive genomewide scan revealed a common haplotype on chromosome 2q21 in seven of the eight patients with PTC. To verify the significance of the 2q21 locus, we performed linkage analysis in an independent sample set of 80 pedigrees, yielding a multipoint heterogeneity LOD score (HLOD) of 3.07 (alpha=0.42), nonparametric linkage (NPL) 3.19, (P=.001) at marker D2S2271. Stratification based on the presence of at least one case of the follicular variant of PTC, the phenotype observed in the Tas1 family, identified 17 such pedigrees, yielding a maximal HLOD score of 4.17 (alpha=0.80) and NPL=4.99 (P=.00002) at markers AFMa272zg9 and D2S2271, respectively. These results indicate the existence of a susceptibility locus for familial NMTC on chromosome 2q21.

Mapping a dominant form of multinodular goiter to chromosome Xp22

Multinodular goiter (MNG) is a common disorder characterized by a nodular enlargement of the thyroid gland and occurring with a female&rcolon;male ratio of 5&rcolon;1. This article reports the analysis of an Italian three-generation pedigree MNG, including 10 affected females and 2 affected males. After linkage to candidate regions previously implicated in various forms of goiter was excluded, a novel MNG locus was searched. Because no male-to-male transmission was present in the study pedigree, an X-linked autosomal dominant pattern of inheritance was hypothesized. Therefore, 18 markers spaced at 10-cM intervals on the X chromosome were examined. A significant LOD score was observed in the Xp22 region, where marker DXS1226 generated a maximum LOD score of 4.73 at a recombination fraction of 0. Analysis of six flanking microsatellites confirmed these data, and haplotype inspection delimited a 9.6-cM interval lying between DXS1052 and DXS8039.