Thyrotropin preparations are mitogenic for thyroid epithelial cells in follicles in suspension culture

COVID-19 associated thyroid dysfunction and other comorbidities and its management using phytochemical-based therapeutics: a natural way

The present severe acute respiratory syndrome-2 (SARS-CoV-2) mediated Coronavirus pandemic (COVID-19) and post-COVID-19 complications affect human life drastically. Patients who have been cured of COVID-19 infection are now experiencing post-COVID-19 associated comorbidities, which have increased mortality rates. The SARS-CoV-2 infection distresses the lungs, kidneys, gastrointestinal tract, and various endocrine glands, including the thyroid. The emergence of variants which includes Omicron (B.1.1.529) and its lineages threaten the world severely. Among different therapeutic approaches, phytochemical-based therapeutics are not only cost-effective but also have lesser side effects. Recently a plethora of studies have shown the therapeutic efficacy of various phytochemicals for the treatment of COVID-19. Besides this, various phytochemicals have been found efficacious in treating several inflammatory diseases, including thyroid-related anomalies. The method of the phytochemical formulation is quick and facile and the raw materials for such herbal preparations are approved worldwide for human use against certain disease conditions. Owing to the advantages of phytochemicals, this review primarily discusses the COVID-19-related thyroid dysfunction and the role of key phytochemicals to deal with thyroid anomaly and post-COVID-19 complications. Further, this review shed light on the mechanism via which COVID-19 and its related complication affect organ function of the body, along with the mechanistic insight into the way by which phytochemicals could help to cure post-COVID-19 complications in thyroid patients. Considering the advantages offered by phytochemicals as a safer and cost-effective medication they can be potentially used to combat COVID-19-associated comorbidities.

Ex vivo model for elucidating the functional and structural differentiation of the embryonic mouse thyroid

Terminal thyroid gland differentiation - the last developmental step needed to enable thyroid hormone (T4) synthesis - involves profound structural and biochemical changes in the thyroid follicular cells (TFCs). We aimed to develop an ex vivo thyroid model of embryonic mouse thyroid that would replicate the in vivo TFC differentiation program. E13.5 thyroid explants were cultured ex vivo in chemically defined medium for 7 days. Immunostaining and qPCR of thyroid explants showed thyroglobulin production onset, follicle formation, and T4 synthesis onset in 1-, 3-, and 5-day-old cultures, respectively. Differentiation was maintained and follicular growth continued throughout the 7-day culture period. Pharmacological approaches to culture inhibition were performed successfully in the ex vivo thyroids. Our robust and well described ex vivo thyroid culture model replicates the sequence of thyroid differentiation to T4 synthesis seen in vivo. This model can be used to test the effects of pharmacological inhibitors on thyroid hormone production.

Acrylamide: review of toxicity data and dose-response analyses for cancer and noncancer effects

Acrylamide (ACR) is used in the manufacture of polyacrylamides and has recently been shown to form when foods, typically containing certain nutrients, are cooked at normal cooking temperatures (e.g., frying, grilling or baking). The toxicity of ACR has been extensively investigated. The major findings of these studies indicate that ACR is neurotoxic in animals and humans, and it has been shown to be a reproductive toxicant in animal models and a rodent carcinogen. Several reviews of ACR toxicity have been conducted and ACR has been categorized as to its potential to be a human carcinogen in these reviews. Allowable levels based on the toxicity data concurrently available had been developed by the U.S. EPA. New data have been published since the U.S. EPA review in 1991. The purpose of this investigation was to review the toxicity data, identify any new relevant data, and select those data to be used in dose-response modeling. Proposed revised cancer and noncancer toxicity values were estimated using the newest U.S. EPA guidelines for cancer risk assessment and noncancer hazard assessment. Assessment of noncancer endpoints using benchmark models resulted in a reference dose (RfD) of 0.83 microg/kg/day based on reproductive effects, and 1.2 microg/kg/day based on neurotoxicity. Thyroid tumors in male and female rats were the only endpoint relevant to human health and were selected to estimate the point of departure (POD) using the multistage model. Because the mode of action of acrylamide in thyroid tumor formation is not known with certainty, both linear and nonlinear low-dose extrapolations were conducted under the assumption that glycidamide or ACR, respectively, were the active agent. Under the U.S. EPA guidelines (2005), when a chemical produces rodent tumors by a nonlinear or threshold mode of action, an RfD is calculated using the most relevant POD and application of uncertainty factors. The RfD was estimated to be 1.5 microg/kg/day based on the use of the area under the curve (AUC) for ACR hemoglobin adducts under the assumption that the parent, ACR, is the proximate carcinogen in rodents by a nonlinear mode of action. When the mode of action in assumed to be linear in the low-dose region, a risk-specific dose corresponding to a specified level of risk (e.g., 1 x 10-5) is estimated, and, in the case of ACR, was 9.5 x 10-2 microg ACR/kg/day based on the use of the AUC for glycidamide adduct data. However, it should be noted that although this review was intended to be comprehensive, it is not exhaustive, as new data are being published continuously.

Reactive oxygen species and Udx1 during early sea urchin development

Sea urchin fertilization is marked by a massive conversion of molecular oxygen to hydrogen peroxide by a sea urchin dual oxidase, Udx1. This enzyme is essential for completing the physical block to polyspermy. Yet, its expression is maintained during development, as indicated by the presence of both Udx1 mRNA and Udx1 protein enriched at the surface of all non-mesenchymal blastomeres. When hydrogen peroxide synthesis by Udx1 is inhibited, either pharmacologically or by specific antibody injection, cleavage is delayed. Application of exogenous hydrogen peroxide, however, partially rescues a fraction of these defective embryos. We also report an unequal distribution of reactive oxygen species between sister blastomeres during early cleavage stages, suggesting a functional role for Udx1 in intracellular signaling.

Recombinant human TSH-aided radioiodine treatment of advanced differentiated thyroid carcinoma: a single-centre study of 54 patients

We sought to evaluate the efficacy, biochemical effects, safety and outcome of recombinant human thyroid-stimulating hormone (rhTSH) as an adjunct to radioiodine treatment of advanced differentiated thyroid carcinoma (DTC). We also sought to determine whether rhTSH is useful as an adjunct to radioiodine treatment following isotretinoin re-differentiation therapy of DTC metastases that have lost function. Therefore, in 54 consecutive patients who had retained bulky metastatic and/or locoregional lesions of DTC despite the exhaustion of other therapeutic options, we gave one to four courses of two consecutive daily intramuscular injections of rhTSH, 0.9 mg, followed by a therapeutic activity of (131)I per os on day 3. Fifty patients had received prior radioiodine treatment aided by l-thyroxine (T(4)) withdrawal. We included in the study 23 patients who had received a trial of isotretinoin therapy for re-differentiation of confirmed de-differentiated metastases. In a blinded, within-patient comparison of post-therapy whole-body scans after the first rhTSH-aided and latest withdrawal-aided treatments in patients with functional metastases at baseline, 18 of 27 (67%) scan pairs were concordant, four (15%) were discordant in favour of the rhTSH-aided scan and five (19%) were discordant in favour of the withdrawal-aided scan. In total, 37 (74%) of 50 paired scans were concordant, eight (16%) favoured rhTSH and five (10%) favoured withdrawal. All differences appeared to be attributable to clinical causes, not to any difference between endogenous and exogenous TSH stimulation. Reflecting the biochemical activity of rhTSH and the release of thyroglobulin (Tg) due to tumour destruction, median serum Tg concentration rose approximately fourfold between baseline and day 6 of the rhTSH-aided treatment course. rhTSH was well tolerated, with mostly minor, transient toxicity, except for neck oedema in three patients with neck infiltrates and pathological spine fracture in one patient with a large vertebral metastasis. At 6 months, complete response occurred in one (2%), partial response in 12 (26%) and disease stabilisation in 19 (40%) of 47 evaluable patients. The rate of complete + partial response was 41% and that of disease stabilisation, 30%, in the 27 evaluable patients with functional metastases at baseline; the corresponding rates were 10% and 55% in the 20 evaluable patients with non-functional metastases at baseline. Although within-patient comparison of early outcome after both modalities is limited by a significantly greater median number of courses and a greater median cumulative activity of radioiodine given under withdrawal, response to rhTSH-aided and withdrawal-aided treatment was similar in 23 (52%) of 44 evaluable patients, superior with rhTSH in 12 (27%) and superior with withdrawal in seven (16%). In two patients, a superior response was obtained after isotretinoin pretreatment and rhTSH and attributed to re-differentiation therapy. In conclusion, our study provides preliminary evidence that rhTSH safely and effectively aids radioiodine treatment of advanced DTC, and does so to an at least equivalent degree as does T(4) withdrawal.

Regulation of thyroid cell proliferation by TSH and other factors: a critical evaluation of in vitro models

TSH via cAMP, and various growth factors, in cooperation with insulin or IGF-I stimulate cell cycle progression and proliferation in various thyrocyte culture systems, including rat thyroid cell lines (FRTL-5, WRT, PC Cl3) and primary cultures of rat, dog, sheep and human thyroid. The available data on cell signaling cascades, cell cycle kinetics, and cell cycle-regulatory proteins are thoroughly and critically reviewed in these experimental systems. In most FRTL-5 cells, TSH (cAMP) merely acts as a priming/competence factor amplifying PI3K and MAPK pathway activation and DNA synthesis elicited by insulin/IGF-I. In WRT cells, TSH and insulin/IGF-I can independently activate Ras and PI3K pathways and DNA synthesis. In dog thyroid primary cultures, TSH (cAMP) does not activate Ras and PI3K, and cAMP must be continuously elevated by TSH to directly control the progression through G(1) phase. This effect is exerted, at least in part, via the cAMP-dependent activation of the required cyclin D3, itself synthesized in response to insulin/IGF-I. This and other discrepancies show that the mechanistic logics of cell cycle stimulation by cAMP profoundly diverge in these different in vitro models of the same cell. Therefore, although these different thyrocyte systems constitute interesting models of the wide diversity of possible mechanisms of cAMP-dependent proliferation in various cell types, extrapolation of in vitro mechanistic data to TSH-dependent goitrogenesis in man can only be accepted in the cases where independent validation is provided.

Influence of transforming growth factor beta1 (TGF-beta1) on the behaviour of porcine thyroid epithelial cells in primary culture through thrombospondin-1 synthesis

Transforming growth factor beta1 (TGF-beta1) is a secreted polypeptide that is thought to play a major role in the regulation of folliculogenesis and differentiation of thyroid cells. On porcine thyroid follicular cells cultured on plastic substratum, TGF-beta1, in a concentration-dependent way, promoted the disruption of follicles, cell spreading, migration and confluency by a mechanism that did not involve cell proliferation. TGF-beta1 strongly activated the production of thrombospondin-1 and (alpha)vbeta3 integrin in a concentration-dependent manner whereas the expression of thyroglobulin was unaffected. Anisomycin, an inhibitor of protein synthesis, inhibited the effect of TGF-beta1 on cell organization. Thrombospondin-1 reproduced the effect of TGF-beta1. In the presence of thrombospondin-1 cells did not organize in follicle-like structures but, in contrast, spreaded and reached confluency independently of cell proliferation. This effect is suppressed by an RGD-containing peptide. The adhesive properties of thrombospondin-1 for thyroid cells were shown to be mediated by both the amino-terminal heparin-binding domain and the RGD domain of thrombospondin-1. Adhesion was shown to involve (alpha)vbeta3 integrin. The results show that TGF-beta1 exerted an influence upon function and behaviour of follicle cells partly mediated by the synthesis of thrombospondin-1 and of its receptor (alpha)vbeta3 integrin.

Role of tight junctions in establishing and maintaining cell polarity

The tight junction (TJ) is not randomly located on the cell membrane, but occupies a precise position at the outermost edge of the intercellular space and, therefore, is itself considered a polarized structure. This article reviews the most common experimental approaches for studying this relationship. We then discuss three main topics. (a) The mechanisms of polarization that operate regardless of the presence of TJs: We explore a variety of polarization mechanisms that operate at stages of the cell cycle in which TJs may be already established. (b) TJs and polarity as partners in highly dynamic processes: Polarity and TJs are steady state situations that may be drastically changed by a variety of signaling events. (c) Polarized distribution of membrane molecules that depend on TJs: This refers to molecules (mainly lipids) whose polarized distribution, although not the direct result of TJs, depends on these structures to maintain such distribution.

Effect of thyroid-stimulating hormone on cultured thyrocytes obtained from patients with Graves' disease and inhibitive effect by sodium iodide: a functional study

Thyrocytes obtained from patients with Graves' disease were cultured for 3 days. This was followed by culture with 10 mU/mL thyroid stimulating hormone (TSH) (TSH group), TSH and sodium iodide (Nal group), or without (control group) for 3 additional days. On the 8th culture day, the amounts of intra- and extra-cellular cyclic adenosine monophosphate (cAMP), extracellular cAMP and thyroglobulin (TG), peroxidase (PO) activity, and cell numbers were measured. The amounts of intra- and extra-cellular cAMP correlated well. TSH increased the values of cAMP, TG and PO to levels higher than those of the control group. As the amount of Nal added to the medium increased, these values decreased. Addition of 10(-5) mol/L Nal lowered the value of cAMP only. When 10(-4) mol/L Nal was added, these three levels were lower than those of the TSH group and the value of cAMP was almost equal to that of the control group. On cell number, no difference was found between the cells cultured with TSH, TSH and Nal, and without TSH or Nal. When the thyrocytes were cultured with 1 mmol/L dibutyryl cAMP sodium salt or 8-bromoadenosine 3',5'-cyclic monophosphate instead of TSH, 10(-4) mol/L Nal did not lower the values of thyroglobulin and peroxidase activity. These results suggest that the Nal blocks the intracellular signal transduction provoked by TSH, only at the cAMP production level.

Growth requirements and oncogene expression in the human thyroid cell line SGHTL-34

The SV40 T-antigen-transfected human thyroid cell line SGHTL-34 was used to investigate the effect of thyrotropin (TSH), insulin-like growth factor-1 (IGF-1) and epidermal growth factor (EGF) on c-fos and c-erbB/EGF receptor (EGF-R) mRNA expression and their role in human thyroid cell proliferation. EGF caused a transient 8- and 4-fold increase in c-fos mRNA level after 30 min in serum/hormone-deprived and in logarithmically growing cells, respectively. EGF was only mitogenic in the presence of serum, as measured by 3H-thymidine incorporation and cell counting. TSH had no detectable effect on c-fos mRNA expression and no mitogenic effect on the SGHTL-34 cells. IGF-1 showed no effect alone or in combination with EGF or TSH on either proliferation or c-fos mRNA expression. Our data suggest that increased c-fos mRNA levels are part of the mitogenic pathway, but are insufficient to engender a mitogenic response. SGHTL-34 cells produced high levels of transforming growth factor-alpha (TGF-alpha) and c-erbB/EGF-R mRNA, also seen in thyroid papillary carcinomas. The TGF-alpha protein was detected in conditioned medium from the SGHTL-34 cells, indicating that TGF-alpha may function as an autocrine growth factor. Our data show that the c-erbB/EGF-R mRNA level is regulated by growth factors and hormones in the SGHTL-34 cell line. The SGHTL-34 cells may therefore represent a useful model system for studying the role of TGF-alpha and EGF-R in thyroid carcinogenesis.

Mutational activation of RAS and GSP oncogenes in differentiated thyroid cancer and their biological implications

Activating mutations of ras-genes (Kirsten-ras, Harvey-ras, N-ras) and genes encoding for the alpha subunit of G-proteins (Gs, Gi2, Gi3, Go, Gz) were assessed in 32 differentiated thyroid cancer (DTC) tissues from German (n = 22) and American (n = 10) patients. Gs-protein (GSP) and/or ras mutations were found in 69% of all tissues with a heterogeneous distribution pattern. An increased prevalence could be demonstrated in metastatic (8 of 9 mutation positive) when compared to localized disease (13 of 23 mutation positive) (p less than 0.001) and in patients greater than 50 years of age (16 of 18 mutation positive), when compared to younger patients (6 of 14 mutation positive) (p less than 0.001). No activating mutations were found on H-ras and K-ras genes nor on genes encoding for the alpha subunits of Gi2, Gi3, Go, and Gz. Differentiated thyroid cancer tissue from German patients revealed a higher prevalence for GSP mutations (73%) than did DTC from American patients (20%) (p less than 0.001). We demonstrated a high frequency of ras and GSP mutations in DTC and suggest that these mutations may contribute to our basic understanding of this disease and might initiate a new search for more rational and individualized therapeutic approaches in patients with DTC.

Growth regulation of normal thyroids and thyroid tumors in man

Our studies using thyrocyte membranes from different human thyroid tissues, monolayer cultures of human thyrocytes, and the permanant cell line FTC-133 demonstrate the stimulatory effect of TSH on metabolism, DNA synthesis, and cell growth in human thyrocytes. Up- and down-regulation of cAMP cell content fails to show direct effects on DNA synthesis and cell growth in primary thyrocyte cultures in man. Increased AC responsiveness to TSH in adenomatous human thyroid tissues, when compared to normal thyroids of the same patient (p less than 0.005), is thus of only questionable importance for thyroid tumor growth. The permanant cell line FTC-133 was established from differentiated follicular human thyroid cancer cells. FTC-133 cells proved to be of particular usefulness in assessing growth regulation of human thyroid tissue. These cells could be propagated in serum free medium, showed thyroglobulin immunoreactivity and EGF receptors, lacked any fibroblast contamination, and responded to TSH and local active growth factors such as EGF and IGF with a stimulated [3H]thymidine incorporation. The latter could be shown in primary cell cultures of normal and pathological human thyrocytes as well. Additional to the stimulatory effect of TSH and IGF on [3H]thymidine incorporation, these substances show an additive effect when incubated simultaneously. Locally active growth factors and endocrine growth stimulation by TSH therefore act synergistically on thyrocyte growth in human thyrocyte cultures. Whether the TSH effect on cell growth is related to its stimulation of AC remains as yet questionable.

Treatment of endemic goitre due to iodine deficiency with iodine, levothyroxine or both: results of a multicentre trial

Preliminary clinical studies and recent in vitro investigations suggest that iodine administration may be an effective alternative in the treatment of the diffuse euthyroid goitre of iodine deficiency. Therefore a 12-month multicentre study was initiated in which 166 patients were randomly assigned to take either 150 micrograms levothyroxine day-1 (group A, n = 61), 400 micrograms iodine day-1 (group B, n = 50), or a combination of 75 micrograms levothyroxine and 200 micrograms iodine day-1 (group C, n = 55) for 8 months with follow-up examinations at 4 and 8 months as well as 4 months after cessation of treatment. Initially, thyroid volume, as determined by ultrasound, was not significantly different in the three groups. In all three groups, during treatment a significant and comparable mean decrease in goitre size was documented (-32.1% in group A, -37.3% in group B, -38.7% in group C). After cessation of treatment in group A mean thyroid volume again increased to near the baseline value (-12.0% compared to the initial investigation), while the therapeutic effect was sustained in group B (-32.5%). In group C, only a slight rebound effect was observed (-26.3% vs baseline volume). Total thyroxine (T4) increased sharply and significantly in group A from 7.8 +/- 1.9 to 10.9 +/- 2.8 micrograms dl-1 after 8 months (P less than 0.001), but only slightly, although significantly in group B (from 7.8 +/- 1.5 micrograms dl-1 to 8.9 +/- 1.6 micrograms dl-1; P less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Iodine vs thyroxine. A changing concept of therapy in endemic goiter?

The hypothesis that goitrogenesis in iodine deficiency can be attributed to the stimulatory effect of thyrotropin (TSH) on the thyroid gland and has long been held to be valid. The task of this review is to describe the reasons why this concept is being challenged. In addition, we report on the autoregulation of the thyroid gland and on in vitro investigations dealing with TSH as a growth factor, which have yielded conflicting results. Finally, we summarize preliminary studies comparing the therapeutic effect of thyroxine and iodine on goiter size. In comparison to thyroxine, iodine application in doses of 300-500 micrograms/day may represent an equally effective way of treatment in areas of endemic goiter, especially in younger patients. In this age group, the risk of side-effects, e.g., iodine-induced thyrotoxicosis, should be low.

Factors influencing the growth of normal and neoplastic thyroid tissue

TSH activates the adenylate cyclase and the phosphoinositide turnover-protein kinase C-calcium systems in thyroid cells and appears to have an important but variable role in controlling the growth of both normal and neoplastic thyroid tissues. Species differences, experimental conditions, and tissue or tumor cell heterogeneity may account for this variability. Although TSH seems to be an important physiologic growth factor, it is neither the exclusive growth factor for the thyroid gland nor absolutely necessary for the effect of other thyroid growth factors. TSH may work in concert with other growth factors such as EGF. Some growth factors influence thyroid growth through TSH, whereas others do not.

Induction of DNA synthesis in dog thyrocytes in primary culture: synergistic effects of thyrotropin and cyclic AMP with epidermal growth factor and insulin

We have investigated the growth effects of thyrotropin (TSH) (mimicked by forskolin and acting through cyclic AMP), epidermal growth factor (EGF), serum (10%) and insulin on quiescent dog thyroid epithelial cells in primary culture in a serum-free defined medium. These cells were previously shown to retain the capacity to express major thyroid differentiation markers. In the presence of insulin and after a similar prereplicative phase of 18 +/- 2h, TSH, EGF, and serum promoted DNA synthesis in such quiescent cells only a minority of which had proliferated in vitro before stimulation. The combination of these factors induced more than 90% of the cells to enter S phase within 48 h and near exponetial proliferation. Analysis of the cell cycle parameters of the stimulated cells revealed that the G1 period duration was similar to the length of the prereplicative phase of quiescent thyroid cells; this might indicate that they were in fact in an early G1 stage rather than in G0 prior to stimulation. TSH and EGF action depended on or was potentiated by insulin. Strikingly, nanomolar concentrations of insulin were sufficient to support stimulation of DNA synthesis by TSH, while micromolar concentrations of insulin were required for the action of EGF. This suggests that insulin supported the action of TSH by acting on its own high affinity receptors, whereas its effect on EGF action would be related to its somatomedinlike effects at high supraphysiological concentrations. Insulin stimulated the progression in the prereplicative phase initiated by TSH or forskolin. In addition, in some primary cultures TSH must act together with insulin to stimulate early events of the prereplicative phase. In the presence of insulin, EGF, and forskolin, an adenylate cyclase activator, markedly synergized to induce DNA synthesis. Addition of forskolin 24 h after EGF or EGF 24 h after forskolin also resulted in amplification of the growth response but with a lag equal to the prereplicative period observed with the single compound. This indicates that events induced by the second factor can no longer be integrated during the prereplicative phase set by the first factor. These findings demonstrate the importance of synergistic cooperation between hormones and growth factors for the induction of DNA synthesis in epithelial thyroid cells and support the proposal that essentially different mitogenic pathways--cyclic AMP-dependent or independent--may coexist in one cell.

Negative effect of iodide on the survival of newly divided epithelial cells in chronically stimulated rat thyroid

The aim of this work was to investigate some aspects of the thyroid epithelial cell kinetics during the iodide-induced involution of a hyperplastic goitre in the rat. Rats were made iodine-deficient for 6 months, and propylthiouracil (PTU) (0.15%) was added to the diet during the last 2 months. Thereafter, rats were refed with iodide and PTU was removed (day 0). Forty-eight hours previously, all the rats were injected with tritiated thymidine ([3H]TdR) (1 microCi/g). Some animals were killed 1 hr or 24 hr after [3H]TdR injection (i.e. on day -2 and -1, day 0 corresponding to the restoration of a normal iodine diet); the other animals were killed after different delay periods and following [3H]TdR injection. Autoradiography of thyroid sections, iodine determination of plasma iodide and protein-bound iodine (PBI), and RIA of plasma thyroid stimulatory hormone (TSH) were performed. Plasma TSH concentration was very high on day 0 of iodide refeeding (3000 +/- 330 ng/ml) and remained at this level until day 8. Plasma PBI was very low on day 0, remained so until day 4 and greatly increased on day 8. Plasma iodide was also very low on day 0, but markedly increased on day 1, then did not vary significantly until day 43 of iodine refeeding. Thyroid weight, elevated on day 0, decreased relatively quickly until day 30, then more slowly until day 73. The [3H]TdR labelling index (LI) of the thyroid epithelial cells (TEC) was high on day 0 (56 +/- 3 labelled cells/10,000 cells), and 24 hr thereafter increased to 104 +/- 3, by division of the labelled cells. On day 1 of iodine refeeding, the LI had abruptly decreased to about half this value and then remained stable for 3 more days. Between day 4 and day 16, a progressive decline in the LI, (by about 3-4 per day), was observed. The LI showed no further modification, up to day 73, the longest period investigated. The decrease in LI occurred without any significant changes in the labelling intensity (grain count) of the remaining labelled cells between day 1 and 16, this indicates that no cell division took place during this period. The data are therefore interpreted as showing a biphasic elimination after iodide refeeding, of cells that were actively proliferating during the goitrous state.(ABSTRACT TRUNCATED AT 400 WORDS)

Morphological demonstration and quantification of TSH binding sites in neoplastic and non-neoplastic thyroid tissues. An autoradiographic study using 125I-labelled thyrotropin

We have developed a morphological method to portray TSH binding sites in intact tissue specimens. Frozen sections were incubated with 125I-labelled TSH so as to localise binding sites by autoradiography. The proof of specificity was substantiated by: the competitive inhibition of 125I-TSH-labelling with cold TSH, the lack of binding in non-target tissues and a lack of binding in TSH target tissues after incubation with 125I-hCG or free 125I. In applying this method to a total of 22 surgical specimens of thyroid, striking differences came to light in respect of the degree to which 125I-TSH binding occurred in the various thyroid disorders. When compared with histologically normal tissue, labelling was generally decreased in toxic adenomas, non-functioning adenomas (cold nodules), and thyroids affected by Graves' disease, whereas non-toxic colloid goitre cases clearly exhibited denser binding. Medullary and anaplastic carcinomas exhibited no specific labelling whilst binding varied in the differentiated carcinomas between no effective binding or a level resembling that found in normal thyroid tissue.

Functional properties of normal and inverted rat thyroid follicles in suspension culture

Rat thyroid follicles in both the normal and the inverted configuration have been cultured in suspension. It has been found that normal follicles (i.e., those having a structural organization similar to the follicles in vivo) express most functional properties of the thyroid gland. They trap iodide, synthesize, secrete, and iodinate thyroglobulin, and secrete thyroid hormone into the culture medium. On the contrary, in inverted follicles (i.e., those having a cell polarity reversed with respect to normal) we were unable to detect expression of some of these functions. We conclude that both the follicular organization and the proper cell polarity are needed for the full expression of thyroid functional properties.

Differentiated thyroid cancer in children

Differentiated thyroid cancer in children remains a controversial disease entity. Its incidence has markedly declined over the last decade since the use of radiotherapy in the treatment of benign conditions of the head, neck, and thorax was abandoned. Other etiologic factors have become relatively more important. The clinical presentation of childhood thyroid cancer is similar to that found in adults, except for a higher frequency of local and distant metastases at the time of initial diagnosis. The specificity and sensitivity of diagnostic tests are limited; however, like in adults, fine-needle aspiration compares favorably with other available diagnostic methods. The therapeutic approach to a child with thyroid cancer represents the most controversial issue associated with the disease. This review provides a discussion of the rationale for the different therapeutic options and emphasizes the excellent prognosis and survival rates, especially when patients are subjected to aggressive treatment with total thyroidectomy followed by the administration of radioactive iodine.

Detection of thyroid growth immunoglobulins (TGI) by [3H]-thymidine incorporation in cultured rat thyroid follicles

A new bioassay is described for detecting the growth stimulating immunoglobulins (TGI) that contribute to goitre formation in human thyroid autoimmune diseases. It measures the incorporation of tritiated thymidine into intact rat thyroid follicles grown in tissue culture. This radiometric assay demands much less technical skill than the cytochemical bioassays (CBA) previously employed. It has good reproducibility and the techniques and apparatus are available in many clinical laboratories. Immunoglobulins (Igs) from 68% of patients with goitrous Graves' disease were positive, in proportion with goitre size, and this showed no correlation with T3 levels, or three accepted methods for conventional thyroid stimulating antibodies. Non-toxic nodular goitre cases gave positive results in 3/9 who had recurrences after one or more thyroidectomies and in 1/10 cases of familial simple goitre. All normal subjects and all endemic goitre cases were negative as well as 21 cases of sporadic non-toxic nodular goitre. Although it is less sensitive than the 'growth CBA' it clearly emphasizes the essential difference between the intensity of growth stimulus which leads to the regular hyperplasia of thyroid epithelium seen in Graves' thyrotoxicosis and the disorganized and metabolically uncoordinated hyperplasia typical of non-toxic nodular goitre.

Stimulation by thyrotropin and cyclic AMP of the proliferation of quiescent canine thyroid cells cultured in a defined medium containing insulin

We have developed serum-free primary cultures of differentiated follicular dog thyroid cells which allow the study of the hormonal control of cell proliferation. The cooperation of insulin and increasing cellular cyclic AMP by thyrotropin triggers the DNA synthesis and the proliferation. Dog thyroid cells are an example of a system in which cyclic AMP is a sufficient signal to stimulate the proliferation in quiescent cells.

Ultrastructure of intermediate stages in polarity reversal of thyroid epithelium in follicles in suspension culture

Separated thyroid follicles can be maintained in suspension culture in Coon's modified F-12 medium in 0.5% calf serum. If the serum concentration is raised to 5%, the follicles undergo inversion in 3-5 d. During the process of inversion, epithelial cells can be observed in intermediate stages of polarity reversal. The earliest ultrastructural changes recognized are surface changes in which tight junctions and microvilli appear at the lateral margins of the cell near the medium. Later, changes in the distribution of intracellular organelles occur. The Golgi apparatus shifts towards the end of the cell facing the medium, and lysosomes shift toward the luminal end of the cell. The right junctions and microvilli at the luminal end of the cell disappear sometime after the cytoplasmic organelles rearrange. The luminal colloid disappears only after the surface changes (loss of tight junctions and microvilli) occur at the luminal end of the cell. There appears to be some regulation of the order in which changes occur during polarity reversal of the thyroid epithelial cell.