Primary 3D Culture of Human Thyroid Follicle-Like Structures in Platelet Lysate-Based Gel.

The results of 3D culturing of human thyroid follicle-like structures in a gel based on platelet lysate at the gel-air interface are presented. During culturing up to 4 months, no new follicle-like structures were formed and none were destroyed. During the first 2 months, most follicle-like structures increased in size; then, their grown decelerated, but they retained viability. Ki-67+ cells were observed in the majority of follicle-like structures. Most of them produced thyroglobulin. Follicle-like structures get closer, the number of contacts between them increased, and cluster appeared. Thus, the developed 3D culturing system in a gel based on platelet lysate is an adequate approach for maintaining structure and functional activity of human follicle-like structures in vitro for at least 2 months.

Iodide Transporters in the Endometrium: A Potential Diagnostic Marker for Women with Recurrent Pregnancy Failures.

OBJECTIVE: The element iodine is an essential nutrient utilized by the thyroid glands, and deficiency of this element has been linked to reproductive failures. Iodide transporters are also present in reproductive tissues and cells of embryonic origin such as the endometrium and trophoblasts, respectively. The aim of this study is to understand if levels of iodide transporters are linked to pregnancy outcomes. SUBJECTS AND METHODS: RNA derived from endometrial biopsies from controls or women with recurrent reproductive failures was analyzed utilizing RT-PCR and targeted RNASeq. RESULTS: When compared to controls, women with 2 or more reproductive failures had a significant increase (>5 fold) in mRNA levels of the iodine transporters NIS and PENDRIN, but not thyroglobulin when probed vis RT-PCR. Targeted RNASeq analysis confirmed these findings when another group of patients were analyzed. CONCLUSION: These findings suggest possible abnormal iodine metabolism and a deficiency of iodine in endometrial tissues from some of the women with reproductive failures. We hypothesize from these findings that inorganic iodide and/or iodine is required for optimal cellular function in reproductive tissues, and that iodide transporters may potentially be used as a marker for infertility or for probing potential localized iodine deficiency that may not present in a typical thyroid panel analysis.

Prognostic role of FDG PET/CT in patients with differentiated thyroid cancer treated with 131-iodine empiric therapy.

BACKGROUND: To assess the long-term prognostic value of F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in patients with differentiated thyroid carcinoma (DTC) undergoing empiric radioiodine (RAI) therapy due to raising values of thyroglobulin (Tg). METHODS: Forty-nine patients with histological diagnosis of DTC (31 with papillary and 18 with follicular carcinoma) follow-up for a mean period of 7.9 ±â€Š5 years after empiric RAI therapy were retrospectively analyzed. RESULTS: FDG-PET/CT was negative in 15 (30.6%) patients and positive in 34 (69.4%), whereas postradioiodine therapy whole body scan (t-WBS) was negative in 16 (32.7%) and positive in 33 (67.3%) patients. FDG-PET/CT and t-WBS were in agreement in 32 patients (7 both negative and 25 both positive); on the contrary, in 17 patients there was disagreement between FDG-PET/CT and t-WBS (P =ns). At short-term follow-up, Tg normalized in 19 (38.8%) patients and was unchanged or increased in 30 (61.2%). Of the 15 patients with negative FDG-PET/CT, 11 (73.3%) showed Tg normalization, whereas of the 34 patients with positive FDG-PET/CT, only 8 (23.5%) had Tg normalization (χ =8.9, P < .005). At multivariate analysis, FDG-PET/CT and Tg normalization at short-term follow-up were independent predictors of disease-free survival (χ =26.3, P < .0001), while Tg normalization was the only variable associated with overall survival χ =7.2, P < .01). CONCLUSION: FDG-PET/CT in association with Tg normalization at short-term follow-up may be useful for long-term prognostic stratification in DTC patients.

PDGFRα Regulates Follicular Cell Differentiation Driving Treatment Resistance and Disease Recurrence in Papillary Thyroid Cancer.

Dedifferentiation of follicular cells is a central event in resistance to radioactive iodine and patient mortality in papillary thyroid carcinoma (PTC). We reveal that platelet derived growth factor receptor alpha (PDGFRα) specifically drives dedifferentiation in PTC by disrupting the transcriptional activity of thyroid transcription factor-1 (TTF1). PDGFRα activation dephosphorylates TTF1 consequently shifting the localization of this transcription factor from the nucleus to the cytoplasm. TTF1 is required for follicular cell development and disrupting its function abrogates thyroglobulin production and sodium iodide transport. PDGFRα also promotes a more invasive and migratory cell phenotype with a dramatic increase in xenograft tumor formation. In patient tumors we confirm that nuclear TTF1 expression is inversely proportional to PDGFRα levels. Patients exhibiting PDGFRα at time of diagnosis are three times more likely to exhibit nodal metastases and are 18 times more likely to recur within 5years than those patients lacking PDGFRα expression. Moreover, high levels of PDGFRα and low levels of nuclear TTF1 predict resistance to radioactive iodine therapy. We demonstrate in SCID xenografts that focused PDGFRα blockade restores iodide transport and decreases tumor burden by >50%. Focused PDGFRα inhibitors, combined with radioactive iodine, represent an additional avenue for treating patients with aggressive variants of PTC.

Immunohistochemical Detection of Pax8 and Napsin A in Canine Thyroid Tumours: Comparison with Thyroglobulin, Calcitonin and Thyroid Transcription Factor 1.

Expression of thyroid transcription factor (TTF)-1 corroborates a thyroid origin of neoplasms. Thyroglobulin and calcitonin immunohistochemistry (IHC) can distinguish between a follicular and C-cell origin of thyroid tumours, respectively. Pax8 (expressed by normal canine thyroid follicular cells) and napsin A (expressed mainly by C-cells) labelling was compared with labelling for TTF-1, thyroglobulin and calcitonin in 114 canine proliferative thyroid lesions. All 81 follicular tumours expressed thyroglobulin and were negative for calcitonin; 79/81 (98%) of these tumours expressed TTF-1 and Pax8 and 60/81 (74%) expressed napsin A. All 25 C-cell lesions expressed calcitonin and were negative for expression of thyroglobulin; 22 (88%) were positive for TTF-1, 13 (57%) for Pax8 and 24/24 for napsin A. Six mixed follicular-medullary carcinomas expressed all five markers. Both carcinosarcomas expressed TTF-1 and napsin A, and one each of these tumours expressed thyroglobulin, calcitonin or Pax8. Pax8 expression was also detected in epididymal cells, endometrial cells and vas deferens epithelium, in Sertoli-like ovarian cells, and in some cases of ovarian adenoma, pancreatic carcinoma, renal cell carcinoma and Sertoli cell tumour. Napsin A was also detected in adrenocortical cells, ovarian granulosa cells, epididymal and endometrial cells, as well as in some renal cell carcinomas, pulmonary adenocarcinomas and Sertoli cell tumours. In summary, Pax8 was as sensitive as TTF-1 and slightly less sensitive than thyroglobulin for identification of follicular tumours, but had low sensitivity for C-cell tumours. Napsin A was as sensitive as calcitonin for C-cell neoplasms, but was less sensitive than thyroglobulin for follicular neoplasms. Thus, these markers are sensitive and, except for renal cell carcinoma (for Pax8, napsin A) and pulmonary adenocarcinoma (for napsin A), are specific thyroid tumour markers.

The Effects of Disturbance on Hypothalamus-Pituitary-Thyroid (HPT) Axis in Zebrafish Larvae after Exposure to DEHP.

Di-(2-ethylhexyl) phthalate (DEHP) has the potential to disrupt the thyroid endocrine system, but the underlying mechanism is unknown. In this study, zebrafish (Danio rerio) embryos were exposed to different concentrations of DEHP (0, 40, 100, 200, 400 µg/L) from 2 to 168 hours post fertilization (hpf). Thyroid hormones (THs) levels and transcriptional profiling of key genes related to hypothalamus-pituitary-thyroid (HPT) axis were examined. The result of whole-body thyroxine (T4) and triiodothyronine (T3) indicated that the thyroid hormone homeostasis was disrupted by DEHP in the zebrafish larvae. After exposure to DEHP, the mRNA expressions of thyroid stimulating hormone (tshß) and corticotrophin releasing hormone (crh) genes were increased in a concentration dependent manner, respectively. The expression level of genes involved in thyroid development (nkx2.1 and pax8) and thyroid synthesis (sodium/iodide symporter, nis, thyroglobulin, tg) were also measured. The transcripts of nkx2.1 and tg were significantly increased after DEHP exposure, while those of nis and pax8 had no significant change. Down-regulation of uridinediphosphate-glucuronosyl-transferase (ugt1ab) and up-regulation of thyronine deiodinase (dio2) might change the THs levels. In addition, the transcript of transthyretin (ttr) was up-regulated, while the mRNA levels of thyroid hormone receptors (trα and trß) remained unchanged. All the results demonstrated that exposure to DEHP altered the whole-body thyroid hormones in the zebrafish larvae and changed the expression profiling of key genes related to HPT axis, proving that DEHP induced the thyroid endocrine toxicity and potentially affected the synthesis, regulation and action of thyroid hormones.

A mouse model suggests two mechanisms for thyroid alterations in infantile cystinosis: decreased thyroglobulin synthesis due to endoplasmic reticulum stress/unfolded protein response and impaired lysosomal processing.

Thyroid hormones are released from thyroglobulin (Tg) in lysosomes, which are impaired in infantile/nephropathic cystinosis. Cystinosis is a lysosomal cystine storage disease due to defective cystine exporter, cystinosin. Cystinotic children develop subclinical and then overt hypothyroidism. Why hypothyroidism is the most frequent and earliest endocrine complication of cystinosis is unknown. We here defined early alterations in Ctns(-/-) mice thyroid and identified subcellular and molecular mechanisms. At 9 months, T4 and T3 plasma levels were normal and TSH was moderately increased (∼4-fold). By histology, hyperplasia and hypertrophy of most follicles preceded colloid exhaustion. Increased immunolabeling for thyrocyte proliferation and apoptotic shedding indicated accelerated cell turnover. Electron microscopy revealed endoplasmic reticulum (ER) dilation, apical lamellipodia indicating macropinocytic colloid uptake, and lysosomal cystine crystals. Tg accumulation in dilated ER contrasted with mRNA down-regulation. Increased expression of ER chaperones, glucose-regulated protein of 78 kDa and protein disulfide isomerase, associated with alternative X-box binding protein-1 splicing, revealed unfolded protein response (UPR) activation by ER stress. Decreased Tg mRNA and ER stress suggested reduced Tg synthesis. Coordinated increase of UPR markers, activating transcription factor-4 and C/EBP homologous protein, linked ER stress to apoptosis. Hormonogenic cathepsins were not altered, but lysosome-associated membrane protein-1 immunolabeling disclosed enlarged vesicles containing iodo-Tg and impaired lysosomal fusion. Isopycnic fractionation showed iodo-Tg accumulation in denser lysosomes, suggesting defective lysosomal processing and hormone release. In conclusion, Ctns(-/-) mice showed the following alterations: 1) compensated primary hypothyroidism and accelerated thyrocyte turnover; 2) impaired Tg production linked to ER stress/UPR response; and 3) altered endolysosomal trafficking and iodo-Tg processing. The Ctns(-/-) thyroid is useful to study disease progression and evaluate novel therapies.

Molecular insights into the possible role of Kir4.1 and Kir5.1 in thyroid hormone biosynthesis.

INTRODUCTION: Thyroid morphogenesis is a complex process. Inwardly rectifying potassium (Kir) genes play a role in hormone release, cell excitability, pH and K(+) homeostasis in many tissues. OBJECTIVES: To investigate the thyroid developmental expression of three members, Kir4.1, Kir4.2 and Kir5.1, in mice. To postulate the K(+) channel role in thyroid hormone secretion. MATERIAL AND METHODS: Quantitative RT-PCR analysis of Kir4.1, Kir4.2 and Kir5.1 in mice of different stages (E13.5-E18.5). RESULTS: mRNA for Kir4.1, Kir4.2 and Kir5.1 were identified and increased with age in mice. Both Kir4.1 and Kir4.2 genes are better expressed after E16.5. Kir4.2 greatly increases from E13.5 to E16.5 (p ≤ 0.05). CONCLUSION: Quantitative PCR shows that the mouse thyroid presents increased expression for Kir channels during development. The role of Kir in thyroid morphogenesis and differentiation might be understood in future studies. We speculate that thyroglobulin trafficking might be modulated by Kir4.1/5.1.

Mixed medullary-papillary carcinoma of the thyroid: report of two cases and review of the literature.

Papillary thyroid carcinoma (PTC) and medullary thyroid carcinoma (MTC) are two distinct types of thyroid carcinoma with considerable difference in terms of cellular origin, histopathological appearance, clinical course and prevalence. The histogenetic origin and possible molecular mechanisms responsible for the development of mixed medullary-papillary carcinoma of the thyroid are still unclear. The most widely accepted hypotheses considering co-occurrence of MTC and PTC are stem cell theory, collision effect theory and hostage theory. Herein we describe two rare cases of mixed medullary-papillary thyroid carcinoma with co-occurrence of MTC and PTC which developed with concomitant MEN 2A and different sites of lymph node metastasis in the first patient, while with atypical clinical presentation in the second patient. In conclusion, co-expression of thyroglobulin, synaptophysin and chromogranin by the papillary component of mixed tumor seems to support stem cell theory in our first case, whereas positive staining for calcitonin but not for thyroglobulin in the medullary component of the tumor along with separation of these two tumors from each other by a normal thyroid tissue seem to indicates the likelihood of collision effect theory in our second case.

Autoimmune predisposition in Down syndrome may result from a partial central tolerance failure due to insufficient intrathymic expression of AIRE and peripheral antigens.

Down syndrome (DS), or trisomy of chromosome 21, is the most common genetic disorder associated with autoimmune diseases. Autoimmune regulator protein (AIRE), a transcription factor located on chromosome 21, plays a crucial role in autoimmunity by regulating promiscuous gene expression (pGE). To investigate if autoimmunity in DS is promoted by the reduction of pGE owing to dysregulation of AIRE, we assessed the expression of AIRE and of several peripheral tissue-restricted Ag genes by quantitative PCR in thymus samples from 19 DS subjects and 21 euploid controls. Strikingly, despite the 21 trisomy, AIRE expression was significantly reduced by 2-fold in DS thymuses compared with controls, which was also confirmed by fluorescent microscopy. Allele-specific quantification of intrathymic AIRE showed that despite its lower expression, the three copies are expressed. More importantly, decreased expression of AIRE was accompanied by a reduction of pGE because expression of tissue-restricted Ags, CHRNA1, GAD1, PLP1, KLK3, SAG, TG, and TSHR, was reduced. Of interest, thyroid dysfunction (10 cases of hypothyroidism and 1 of Graves disease) developed in 11 of 19 (57.9%) of the DS individuals and in none of the 21 controls. The thymuses of these DS individuals contained significantly lower levels of AIRE and thyroglobulin, to which tolerance is typically lost in autoimmune thyroiditis leading to hypothyroidism. Our findings provide strong evidence for the fundamental role of AIRE and pGE, namely, central tolerance, in the predisposition to autoimmunity of DS individuals.

Transient covalent interactions of newly synthesized thyroglobulin with oxidoreductases of the endoplasmic reticulum.

Newly synthesized thyroglobulin (Tg), the thyroid prohormone, forms detectable high molecular weight mixed disulfide adducts: until now, only Tg "adduct B" was identified as primarily engaging the endoplasmic reticulum oxidoreductases ERp57 and protein disulfide isomerase. Here, we demonstrate that the faster migrating Tg adduct C primarily engages the CaBP1/P5 oxidoreductase, whereas the slower migrating Tg adduct A primarily engages ERp72. Upon siRNA-mediated knockdown of CaBP1/P5 or ERp72, adducts C or A, respectively, are decreased. Within the three Tg adduct bands that do not exhibit a precursor-product relationship, Tg exhibits distinct oxidation patterns. We present evidence suggesting that disulfide maturation occurs within Tg monomers engaged in each of the adduct bands. Moreover, the same Tg substrate molecules can form simultaneous mixed disulfides with both CaBP1/P5 and protein disulfide isomerase, although these are generally viewed as components of distinct oxidoreductase-chaperone protein complexes. Such substrate-oxidoreductase combinations offer Tg the potential for simultaneous oxidative maturation along different parallel tracks leading to the native state.

Lymph node metastases in papillary thyroid cancer detected by quantitative real-time polymerase chain reaction for thyroglobulin and cytokeratine-19.

Papillary thyroid cancer (PTC) metastases in the lymph nodes (LNs) were detected by real-time polymerase chain reaction (PCR) for TG and cytokeratin 19 (CK19), and the obtained results were compared with histopathology. 107 LNs from 34 PTC patients were divided into four blocks by a special cutting device - 2 for histopathology, while the other 2 were tested by quantitative real-time PCR. Metastases were detected in 20 nodes from 10 (29.4%) patients. TG and CK19 expression levels differed vastly between nodes with and without metastatic cells. ddCt of TG in the genetic material extracted from N0 nodes was 9.97 ±4.20, while in nodes with metastases ddCt was 0.91±4.20 (p < 0.0001). Cytokeratin 19 showed similar results with expression level (ddCt) in N0 nodes of 10.96 ±2.58 vs. 7.73 ±3.63 in nodes with metastases (p < 0.0001). Evaluation of the utility of both parameters showed efficient differentiation of node involvement in the case of TG, with area under the ROC curve (AUC) equal to 0.91 (95% CI: 0.85-0.96). Cytokeratin 19 also allowed for a degree of differentiation but its diagnostic efficacy was lower (AUC 0.76, 95% CI: 0.64-0.88). The combined TG and CK19 quantitative real-time PCR could be used to select a previously missed group of patients with nodal involvement undetectable by standard histopathology.

Morphological and functional deterioration of the rat thyroid following chronic exposure to low-dose PCB118.

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that can severely disrupt the synthesis and secretion of endocrine hormones. To investigate the effects of 2,3',4,4',5-pentachlorobiphenyl (PCB118) on thyroid structure and function, 40 male Wistar rats were divided into 4 equal treatment groups and administered vehicle or one of three doses of PCB118. The experimental groups received intraperitoneal (i.p.) injection of 10, 100, or 1000µg/kg/day PCB118, 5 days per week for 13 weeks, whereas the control group was injected with corn oil (vehicle). Serum concentrations of free thyroxine (FT4), free triiodothyronine (FT3) and thyroid stimulating hormone (TSH) were measured by radioimmunoassays. Histopathological and ultrastructural changes in the thyroid were observed under light microscopy and transmission electron microscopy (TEM). The mRNA expression levels of the sodium-iodide symporter (NIS) and thyroglobulin (TG) were quantified by real-time PCR. Increasing doses of PCB118 resulted in progressively lower FT3, FT4 and TSH concentrations in serum. Injection of PCB118 at all doses led to histopathological deterioration of the thyroid characterized by follicular hyperplasia and expansion, shedding of epithelial cells and fibrinoid necrosis. Follicle cells exhibited swollen or vacuolated endoplasmic reticula, as revealed by TEM. Exposure to PCB118 also caused significant decreases in NIS and TG mRNA expression levels. Chronic exposure to low-dose PCB118 and other PCB congeners may be a significant risk factor for thyroid diseases.

Factors associated with serum thyroglobulin levels in a population living in Belarus.

OBJECTIVE: Serum thyroglobulin (Tg) has been associated with a number of thyroid disorders and has been proposed as an indicator of iodine deficiency in a population. However, few studies have addressed the epidemiology of Tg in a population-based setting or in the context of exposure to radioactive iodine-131 (I-131). Our objective was to evaluate baseline levels of Tg in relation to sociodemographic characteristics, iodine status and thyroid function for individuals exposed to I-131. DESIGN: A population-based cohort assembled in Belarus following the Chornobyl accident provided demographic factors, clinical data and physiological measurements. PARTICIPANTS: Our analytical sample included 10,344 subjects of whom 7890 had no thyroid disease and 2454 had evidence of structural or functional thyroid abnormality. MEASUREMENTS: Standardized assays were used to measure serum Tg, urinary iodine, TSH and antibodies to Tg and thyroid peroxidase. Ultrasound was used to assess the presence of nodules and estimate thyroid volume. RESULTS: In the fully adjusted model, percent change in Tg was significantly increased among females, smokers and subjects of older age and Tg increased with decreasing urinary iodine concentration, increasing serum TSH and increasing thyroid volume (P-values for trend <0·0001), and presence of thyroid nodules (P < 0·05). We found a complex interaction between region of residence, rural/urban living, presence/absence of thyroid abnormalities and serum Tg (P < 0·0001). CONCLUSIONS: In residents of Belarus, serum Tg is significantly related to presence of thyroid abnormalities as well as indicators of thyroid function and iodine deficiency and, therefore, could be used to characterize the iodine status and thyroid function of individuals in the context of epidemiological study.

Radioiodine therapy of thyroid carcinoma following Pax-8 gene transfer.

The thyroid transcription factor Pax-8 could bind with the promoter/enhancer of thyroid-specific genes such as thyroglobulin (Tg), thyroperoxidase (TPO) and sodium iodide symporter (NIS), and regulate the expression of these proteins in thyrocyte. Promoting iodide accumulation in tumor cells by re-expression of Pax-8 provides a possible strategy for radioiodine therapy of tumor. Therefore, we investigated the effect of Pax-8 gene transfer on radioiodine therapy of thyroid carcinoma. The human Pax-8 gene was transfected into the human thyroid carcinoma (K1 and F133) cells by the recombinant adenovirus vector. Although the NIS mRNA was not detected, the expression of mRNA and proteins of Tg and TPO in AdPax-8-infected F133 cells were activated by Pax-8. Iodide uptake in thyroid carcinoma cells was reactivated by Pax-8 (increasing 3.3-fold in K1 cells and 5.7-fold in F133 cells). Moreover, Pax-8 promoted iodide organification and the retention time of iodine in Pax-8-expressing cells apparently prolonged in vitro and in vivo (P<0.05). Pax-8-expressing thyroid carcinoma cells were selectively killed by radioiodine. The AdPax-8-infected tumors in vivo clearly visualized in scanning images at 12 h after administration of radioiodine. These results indicate that Pax-8 can promote iodide uptake, and specifically prolong the retention time of iodide in thyroid cancer in vitro and in vivo by promoting the expression of TPO and Tg proteins. Pax-8 gene transfection may lead to effective radioiodine therapy of tumor.

Thyroid hyperactivity with high thyroglobulin in serum despite sufficient iodine intake in chronic cold adaptation in an Arctic Inuit hunter population.

OBJECTIVE: Adult man hosts brown adipose tissue with the capacity to consume energy and dissipate heat. This is essential for non-shivering thermogenesis and its activation depends on sympathetic activity and thyroid hormones. This led us to evaluate the impact of chronic cold exposure on thyroid activity and thyroid hormones in serum in Arctic residents. DESIGN: Comparative, population-based study (n = 535) performed in Greenland. METHODS: Hunters were compared with other men, and Inuit in remote settlements in East Greenland with no modern housing facilities were compared with the residents of the capital city in West Greenland and residents of a major town in East Greenland in a cross-sectional study. We used interview-based questionnaires, measured TSH, free thyroxine, free triiodothyronine (fT(3)), thyroglobulin (TG) antibody and TG (a measure of thyroid activity) in serum, and iodine and creatinine in spot urine samples. RESULTS: Serum TG was the highest among hunters (P = 0.009) and settlement dwellers (P = 0.001), who were most markedly exposed to cold, even though they had the highest urinary iodine excretion (hunters, P < 0.001; settlement dwellers, P < 0.001). Hunters and settlement dwellers also had the lowest fT(3) (hunters, P < 0.001; settlement dwellers, P < 0.001) after adjusting for gender, age, smoking habits, alcohol intake and iodine excretion in multivariate linear regression models. TSH was not influenced by measures of cold exposure (hunter, P = 0.36; residence, P = 0.91). CONCLUSIONS: Cold exposure influenced thyroid hormones and TG in serum in Arctic populations consistent with consumption of thyroid hormone and higher thyroid hormone turnover. Findings emphasise that changes in thyroid activity are essential in cold adaptation in Arctic residents.

Expression of thyroid-specific transcription factors in thyroid carcinoma, contralateral thyroid lobe and healthy thyroid gland in dogs.

Thyrotropin receptor (TSH-R), thyroglobulin (Tg), thyroperoxidase (TPO), thyroid specific transcription factor-1 (TTF-1), paired box 8 transcription factor (PAX-8), insulin like growth factor-1 (IGF-1) and estrogen receptor alpha (ERα) transcripts were determined by real-time PCR in follicular carcinoma and contralateral (CL) lobes, and healthy thyroid canine glands. Concentrations of TSH-R, PAX-8, and ERα mRNA were not different among groups; the carcinoma group had lower Tg and TPO mRNA than healthy and CL groups, while no differences were found between the two latter groups, suggesting that the carcinoma tissue presents an altered capacity to synthesize thyroid hormones. The transcription factor that promotes thyrocytes proliferation, TTF-1 as well as IGF-1, presented a greater mRNA expression in the CL group, suggesting that the CL lobe may function in a compensatory state.

Ghrelin potentiates TSH-induced expression of the thyroid tissue-specific genes thyroglobulin, thyroperoxidase and sodium-iodine symporter, in rat PC-Cl3 Cells.

Ghrelin is a 28-amino-acid peptide that stimulates pituitary growth-hormone secretion and modulates food-intake and energy metabolism in mammals. It is mainly secreted by the stomach, but it is also expressed in many other tissues such as cartilage or the thyroid gland. In the present study we have analyzed by RT-PCR and using immunohistochemistry and immunofluorescence the expression and tissue distribution of ghrelin and its functional receptor (GHS-R type 1α) in thyroid cell-lines and in normal and pathological rat thyroid tissue. Additionally, by measuring the incorporation of BrdU, we have investigated if, as previously noted for FRTL-5 cells, ghrelin enhances the proliferation rate in the PC-Cl3 rat-thyrocyte cell-line. Finally, we have determined the stimulatory effect of ghrelin on TSH-induced expression of the tissue-specific key genes involved in the synthesis of thyroid hormone: thyroglobulin, thyroperoxidase and sodium-iodine symporter. Our data provide direct evidence that C-cell secreted ghrelin may be involved in the paracrine regulation of the thyroid follicular cell function.