Three-dimensional microscopy and image fusion reconstruction analysis of the thyroid gland during morphogenesis.

Thyroid dysgenesis (TD) is a major cause of primary congenital hypothyroidism; however, the molecular mechanism underlying this process is unclear. Current knowledge regarding the morphogenesis of the thyroid gland and vascular anomalies affecting thyroid development is limited. To monitor the early stages of thyroid gland development, we generated double transgenic zebrafish embryos Tg(tg:mCherry/flk1:EGFP). We described the volume of the thyroid from 2 days postfertilization (dpf) to 5 dpf using 3D reconstruction images. We treated zebrafish embryos with the fibroblast growth factor (FGF) inhibitor PD166866 to better understand the impact of vascular defects on thyroid development and the effects of drug administration at specific time periods on different stages of thyroid development. The 3D reconstruction data revealed that the thyroid glands underwent significant transformation at critical time points. PD166866 treatment from 48 to 72 hours postfertilization (hpf) and from 72 to 96 hpf did not cause obvious reductions in thyroid volume but did result in observable abnormalities in thyroid morphology. The treatment also affected thyroid volume from 36 to 48 hpf, thus indicating that there are time-point-specific effects of drug administration during thyroid development. Three-dimensional image reconstruction provides a comprehensive picture of thyroid anatomy and can be used to complement anatomical fluorescence information. The effects of an FGF pathway inhibitor on thyroid development were determined to be time-point-dependent.

Enhanced Canonical Wnt Signaling During Early Zebrafish Development Perturbs the Interaction of Cardiac Mesoderm and Pharyngeal Endoderm and Causes Thyroid Specification Defects.

Background: Congenital hypothyroidism due to thyroid dysgenesis is a frequent congenital endocrine disorder for which the molecular mechanisms remain unresolved in the majority of cases. This situation reflects, in part, our still limited knowledge about the mechanisms involved in the early steps of thyroid specification from the endoderm, in particular the extrinsic signaling cues that regulate foregut endoderm patterning. In this study, we used small molecules and genetic zebrafish models to characterize the role of various signaling pathways in thyroid specification. Methods: We treated zebrafish embryos during different developmental periods with small-molecule compounds known to manipulate the activity of Wnt signaling pathway and observed effects in thyroid, endoderm, and cardiovascular development using whole-mount in situ hybridization and transgenic fluorescent reporter models. We used the antisense morpholino (MO) technique to create a zebrafish acardiac model. For thyroid rescue experiments, bone morphogenetic protein (BMP) pathway induction in zebrafish embryos was obtained by manipulation of heat-shock inducible transgenic lines. Results: Combined analyses of thyroid and cardiovascular development revealed that overactivation of Wnt signaling during early development leads to impaired thyroid specification concurrent with severe defects in the cardiac specification. When using a model of MO-induced blockage of cardiomyocyte differentiation, a similar correlation was observed, suggesting that defective signaling between cardiac mesoderm and endodermal thyroid precursors contributes to thyroid specification impairment. Rescue experiments through transient overactivation of BMP signaling could partially restore thyroid specification in models with defective cardiac development. Conclusion: Collectively, our results indicate that BMP signaling is critically required for thyroid cell specification and identify cardiac mesoderm as a likely source of BMP signals.

Slc:Wistar/ST rats develop unilateral thyroid dysgenesis: A novel animal model of thyroid hemiagenesis.

Developmental anomalies of the thyroid gland lead to congenital malformations such as thyroglossal duct cysts and thyroid dysgenesis. However, the pathogenesis of thyroid dysgenesis remains unclear due to the lack of suitable animal models. This study demonstrated that Slc:Wistar/ST rats frequently developed unilateral thyroid dysgenesis, including hemiagenesis, characterized by the absence of one lobe. In Wistar/ST rats, each thyroid lobe was frequently different in size, and approximately 27% and 20% of the rats presented with hemihypoplasia and hemiagenesis of the thyroid gland, respectively. Dysgenesis was predominant on the left side in both sexes, without sex differences. At a young age, thyroid hemiagenesis did not alter body weight. In rats of both sexes with thyroid hemiagenesis, plasma total triiodothyronine and total triiodothyronine levels remained unchanged while plasma thyroid-stimulating hormone levels were significantly elevated in young rats. The remaining thyroid lobes increased in weight, but the follicular epithelial cells appeared normal in terms of their height and proliferating activities. On the side of thyroid dysgenesis, the parathyroid glands were normally localized and were situated at the same location as the contralateral glands. The ultimobranchial body remnants were localized at the level of the thyroid gland along with the cranial thyroid artery and vein, forming cell clusters or cystic structures and containing calcitonin-positive C-cells. In conclusion, Wistar/ST rats developed unilateral thyroid dysgenesis and may be novel and useful animal models for thyroid hemiagenesis in humans and for morphogenesis of pharyngeal pouch-derived organs.

99mTc Sodium Pertechnetate Uptake in Ectopic Mediastinal Thyroid Tissue on Hybrid Thyroid Scintigraphy.

Ectopic thyroid is a rare/incidental imaging finding. When discovered, 90% of ectopic thyroid is found typically along the pathway of embryologic migration of thyroid tissue, whereas around 10% have been discovered in other anatomical locations including the mediastinum and the heart. Thyroid scintigraphy with Tc sodium pertechnetate (TcO4) is peculiar for thyroid tissue uptake. The current case, clinically euthyroid, had heterogeneous uptake in multinodular goiter with uptake in the ectopic thyroid tissue in right paratracheal location on functional imaging with TcO4. Subsequent single photon emission computed tomography/computed tomography (SPECT/CT) imaging confirmed the ectopic thyroid tissue.

Hybrid SPECT/CT Helps Characterization and Localization of a Dual Thyroid Ectopia.

The presence of ectopic thyroid tissue in 2 or more different sites is rare. A 12-year-old girl presented with midline anterior neck swelling in the infrahyoid region with subclinical hypothyroidism. Thyroid scanning with Tc-pertechnetate was performed, and SPECT/CT was ordered for further evaluation. Two hyperdense lesions demonstrating intense radiotracer uptake were seen in the midline at the base of the tongue and infrahyoid neck. We emphasis the role of hybrid SPECT/CT for characterization and localization of suspected ectopic thyroid tissue.

New insight into ectopic thyroid glands between the neck and maxillofacial region from a 42-case study.

BACKGROUND: Ectopic thyroid is a rare disease. In the present study at the 9th People's Hospital in Shanghai, China, 42 patients' ectopic thyroid glands between the neck and maxillofacial region were subjected to a retrospective and transverse study based on data from 1978 to 2012 to explore the natural characteristics of ectopic thyroid. METHODS: The patients' clinical data were collected. In addition, scintigraphy (Tc-99 m, Iodine-131), CT scan, histology and pathology were performed. The protein expression of thyroid transcription factor-1 (TTF-1), thyroglobulin (TG), calcitonin (CT), Ki-67 and parathyroid hormone (PTH) were analyzed from paraffin wax-stored specimens of ectopic thyroid tissue compared with those of orthotopic thyroid tissue. RESULTS: There were 42 total ectopic thyroid patients, approximately 1.24 patients per year on average at our hospital. These patients were aged from 6 to 85 years old, and there were 35 females (83.3 %), seven males (16.7 %). In total, 27 of the patients had lingual thyroid (64 %); seven, sublingual thyroid (17 %); five, dual areas occupied by ectopic thyroid (12 %) and three, other types (7 %). The following conditions were also presented: nodular goiter (13 %), adenoma (8.7 %) and Hashimoto's thyroiditis (4.3 %), no malignancy and no accompanying ectopic parathyroid. TTF-1 expression was significantly higher in ectopic samples than that in orthotopic samples (P = 0.007), but CT and Ki-67 levels displayed no difference. PTH was negative in ectopic tissue. CONCLUSION: Ectopic thyroid is a rare disease and females were more prone to the disease. The most frequent location was lingual thyroid. Nodular goiter, adenoma and Hashimoto's thyroiditis was observed as orthotopic thyroid without accompanying ectopic parathyroid. TTF-1 was highly expressed in ectopic tissue, which may be related to abnormal embryogenesis leading to the thyroid gland being in an abnormal position. The expression of calcitonin (CT) and Ki-67 was not increased, and there were no malignant cells in any sample, which could indicate that it is not easy for ectopic thyroids to become malignant between the neck and maxillofacial region.

Conserved Telomere Length in Human Ectopic Thyroids: An Argument Against Premature Differentiation Causing Arrested Migration.

BACKGROUND: In humans, the cause of arrested migration of the median thyroid anlage resulting in an ectopic sublingual gland is unknown. These ectopic glands have a normal follicular architecture but their thyrotropin-induced growth is insufficient, leading to congenital hypothyroidism in the vast majority of affected subjects. We hypothesized that arrested migration is due to premature differentiation [reflected by decreased telomere length (TL)], as observed in neural tube defects in mice. METHODS: Absolute TL and telomerase reverse transcriptase (hTERT) expression was measured in four ectopic and six orthotopic thyroids. TL was measured by quantitative polymerase chain reaction of genomic DNA, whereas hTERT expression was measured by quantitative polymerase chain reaction of total RNA. RESULTS: The mean±standard deviation TL (in kilobases per diploid genome) was 140.45±40.07 in ectopic and 97.50±30.48 in orthotopic thyroids (p=0.12). Expression of hTERT was quiescent in both ectopic and orthotopic thyroids. CONCLUSIONS: Compared with orthotopic thyroids, TL shortening is not observed in ectopic thyroid tissues and, consequently, no compensatory hTERT expression was measured. This makes premature differentiation an unlikely cause of arrested migration and it suggests, indirectly, that ectopic thyroids are not at higher risk of cancer than orthotopic thyroids.

El diagnóstico clínico-molecular en la hipoplasia de cartílago-pelo: dos nuevos casos / Clinical and molecular diagnostics of a cartilage-hair hypoplasia: two new cases

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Functional characterization of the novel sequence variant p.S304R in the hinge region of TSHR in a congenital hypothyroidism patients and analogy with other formerly known mutations of this gene portion.

CONTEXT: Thyroid dysgenesis may be associated with loss-of-function mutations in the thyrotropin receptor (TSHR) gene. OBJECTIVES: The aim of this study was to characterize a novel TSHR gene variant found in one patient harboring congenital hypothyroidism (CH) from a cohort of patients with various types of thyroid defects. MATERIALS AND METHODS: This cross-sectional cohort study involved 118 patients with CH and their family members, including 45 with familial and 73 with sporadic diseases. The thyroid gland was normal in 23 patients, 25 patients had hypoplasia, 25 hemithyroid agenesis, 21 had athyreosis, and 21 had ectopy. Genomic DNA was extracted, and 10 exons of the TSHR gene were amplified and sequenced. Mutations in other candidate genes were investigated. Ortholog alignment was performed, and TSHR functional assays were evaluated. RESULTS: We identified one previously unknown missense variation in the hinge region (HinR) of the TSHR gene (p.S304R) in one patient with thyroid hypoplasia. This variant is conserved in our ortholog alignment. However, the p.S304R TSHR variant presented a normal glycosylation pattern and signal transduction activity in functional analysis. CONCLUSION: We report the ocurrence of a novel nonsynonymous substitution in the HinR of the large N-terminal extracellular domain of the TSHR gene in a patient with thyroid hypoplasia. In contrast with four others in whom TSHR mutations of the hinge portion were previously identified, the p.S304R TSHR variation neither affected TSH binding nor cAMP pathway activation. This TSHR gene variant was documented in a CH patient, but the current data do not support its role in the clinical phenotype.

DYRK1A BAC transgenic mouse: a new model of thyroid dysgenesis in Down syndrome.

The most common thyroid abnormality among Down syndrome (DS) children corresponds to a mildly elevated TSH, with T4 decreased or in the normal range and thyroid hypoplasia, from the neonatal period onward, which aggravate their mental impairment. Transgenic Dyrk1A mice, obtained by bacterial artificial chromosome engineering (mBACTgDyrk1A), have 3 copies of the Dyrk1A gene. The objective is to determine whether this transgenic Dyrk1A (Dyrk1A(+/++)) mouse is an adequate murine model for the study of thyroid dysgenesis in DS. Embryonic thyroid development from embryonic day 13.5 (E13.5) to E17.5 was analyzed in wild-type (WT) and Dyrk1A(+/++) mice by immunofluorescence with anti-Nkx2-1, anti-thyroglobulin, and anti-T4 antibodies, markers of early thyroid development, hormonogenesis, and final differentiation, respectively. The expression of transcription factors Nkx2-1, Pax8, and Foxe1 involved in thyroidogenesis were studied by quantitative RT-PCR at the same embryonic stages. We then compared the adult phenotype at 8 to 12 weeks in Dyrk1A(+/++) and WT mice for T4 and TSH levels, thyroidal weight, and histological analysis. Regarding thyroidal development, at E15.5, Dyrk1A(+/++) thyroid lobes are double the size of WT thyroids (P = .01), but the thyroglobulin stained surface in Dyrk1A(+/++) thyroids is less than a third as large at E17.5 (P = .04) and their differentiated follicular surface half the size (P = .004). We also observed a significant increase in Nkx2-1, Foxe1, and Pax8 RNA levels in E13.5 and E17.5 Dyrk1A(+/++) embryonic thyroids. Dyrk1A(+/++) young adult mice have significantly lower plasma T4 (2.4 ng/mL versus WT, 3.7 ng/mL; P = 0.019) and nonsignificantly higher plasma TSH (114 mUI/L versus WT, 73mUI/L; P = .09). In addition, their thyroids are significantly heavier (P = .04) and exhibit large disorganized regions. Dyrk1A overexpression directly leads to thyroidal embryogenetic, functional and morphological impairment. The young adult thyroid phenotype is probably a result of embryogenetic impairment. The Dyrk1A(+/++) mouse can be considered a suitable study model for thyroid dysgenesis in DS.

TSH compensates thyroid-specific IGF-I receptor knockout and causes papillary thyroid hyperplasia.

Although TSH stimulates all aspects of thyroid physiology IGF-I signaling through a tyrosine kinase-containing transmembrane receptor exhibits a permissive impact on TSH action. To better understand the importance of the IGF-I receptor in the thyroid in vivo, we inactivated the Igf1r with a Tg promoter-driven Cre-lox system in mice. We studied male and female mice with thyroidal wild-type, Igf1r(+/-), and Igf1r(-/-) genotypes. Targeted Igf1r inactivation did transiently reduce thyroid hormone levels and significantly increased TSH levels in both heterozygous and homozygous mice without affecting thyroid weight. Histological analysis of thyroid tissue with Igf1r inactivation revealed hyperplasia and heterogeneous follicle structure. From 4 months of age, we detected papillary thyroid architecture in heterozygous and homozygous mice. We also noted increased body weight of male mice with a homozygous thyroidal null mutation in the Igf1r locus, compared with wild-type mice, respectively. A decrease of mRNA and protein for thyroid peroxidase and increased mRNA and protein for IGF-II receptor but no significant mRNA changes for the insulin receptor, the TSH receptor, and the sodium-iodide-symporter in both Igf1r(+/-) and Igf1r(-/-) mice were detected. Our results suggest that the strong increase of TSH benefits papillary thyroid hyperplasia and completely compensates the loss of IGF-I receptor signaling at the level of thyroid hormones without significant increase in thyroid weight. This could indicate that the IGF-I receptor signaling is less essential for thyroid hormone synthesis but maintains homeostasis and normal thyroid morphogenesis.

Increased serum thyroglobulin levels and negative imaging in thyroid cancer patients: are there sources of benign secretion? A speculative short review.

After thyroidectomy and 131I ablation for differentiated thyroid cancer (DTC), serum thyroglobulin (Tg) became a sensitive marker of residual disease. It is not uncommon to find patients at follow-up with persistent serum Tg levels and no other clinical or imaging evidence for the disease. The vast majority of these patients, most probably, have occult foci of disease, often in minute cervical lymph nodes. A review of the literature including papers published on PubMed/Medline until June 2010 was made. In this study we speculated that a minority of patients who had undergone surgery for differentiated thyroid cancer might have benign sources of Tg secretion at follow-up. These sources may be foci of radio-resistant ectopic thyroid tissue or a thyroid stimulating hormone-stimulated thymus.

Characterization of mutations in the FOXE1 gene in a cohort of unrelated Malaysian patients with congenital hypothyroidism and thyroid dysgenesis.

The FOXE1 gene was screened for mutations in a cohort of 34 unrelated patients with congenital hypothyroidism, 14 of whom had thyroid dysgenesis and 18 were normal (the thyroid status for 2 patients was unknown). The entire coding region of the FOXE1 gene was PCR-amplified, then analyzed using single-stranded conformational polymorphism, followed by confirmation by direct DNA sequencing. DNA sequencing analysis revealed a heterozygous A>G transition at nucleotide position 394 in one of the patients. The nucleotide transition changed asparagine to aspartate at codon 132 in the highly conserved region of the forkhead DNA binding domain of the FOXE1 gene. This mutation was not detected in a total of 104 normal healthy individuals screened. The binding ability of the mutant FOXE1 protein to the human thyroperoxidase (TPO) promoter was slightly reduced compared with the wild-type FOXE1. The mutation also caused a 5% loss of TPO transcriptional activity.

In the Italian population sexual dimorphism affects pre-natal thyroid migration but not biochemical severity of gland ectopia and pre-natal bone maturation.

UNLABELLED: The aim of the present study was to retrospectively re-evaluate a population of selected infants with congenital hypothyroidism (CH), in order to investigate whether sexual dimorphism affects: a) CH etiology; b) its biochemical severity at the time of screening and recall; c) patients' biochemical response to replacement treatment during the 1st yr of life; d) their bone maturation (BM) at birth; e) their psychomotor status at 1 yr. This retrospective study covers 192 infants (116 females) with persistent CH who were selected from a larger population of CH patients identified during a 10-yr period (1990-1999) by the screening programs of 5 northern, central, and southern regions of Italy. Thirty boys (39.5%) and 66 girls (56.9%) were found to have ectopia, whereas the remaining 46 boys and 50 girls exhibited the other causes of CH. When compared with the prevalence of the remaining causes that of ectopia was significantly higher in girls than in boys (66/116 vs 30/76; chi2=5.57, p<0.025), and sex ratio in ectopia was significantly different also compared with the orthotopic gland group only (66/84 vs 30/51; chi2=6.02, p<0.025). No differences between males and females were detected in the groups with either athyreosis or orthotopic gland. In no groups were there differences between sexes for gestational age, birth auxological data, percentage of newborns with bone retardation or developmental quotient at 1 yr. Thyroid tests at birth, age at TSH normalization and average thyroid tests under L-T4 treatment during the 1st yr did not differ between sexes in any of the groups. CONCLUSIONS: a) in the Italian population sexual dimorphism affects pre-natal thyroid migration but neither biochemical severity of ectopia, nor pre-natal bone maturation and psychomotor development; b) girls with CH do not require higher doses of initial therapy in order to achieve TSH normalization; c) future developmental and molecular studies on ectopia etiology in CH need to take into account the effect of sexual dimorphism.