Journal of Clinical and Diagnostic Pathology

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ISSN: 2689-5773
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  • Content of Copper, Iron, Iodine, Rubidium, Strontium and Zinc in Thyroid Malignant Nodules and Thyroid Tissue adjacent to Nodules

    Vladimir Zaichick 1  

    1Prof., Dr. Vladimir Zaichick, Medical Radiological Research Centre, Korolyev St. 4, Obninsk 249036, Russia.

    Abstract

    Thyroid malignant nodules (TMNs) are the most common endocrine cancer. The etiology and pathogenesis of TMNs must be considered as multifactorial. Diagnostic evaluation of TMNs represents a challenge, since there are numerous benign and malignant thyroid disorders that need to be exactly attributed. The present study was performed to clarify the possible role of some trace elements (TEs) as cancer biomarker. For this aim thyroid tissue levels of copper (Cu), iron (Fe), iodine (I), rubidium (Rb), strontium (Sr), and zinc (Zn) were prospectively evaluated in malignant tumor and thyroid tissue adjacent to tumor of 41 patients with TMNs. Measurements were performed using energy-dispersive X-ray fluorescent analysis. Results of the study were additionally compared with previously obtained data for the same TEs in “normal” thyroid tissue. From results obtained, it was possible to conclude that the common characteristics of TMNs in comparison with “normal” thyroid and visually “intact” thyroid tissue adjacent to tumor were drastically reduced level of I. It was supposed that the drastically reduced level of I content in cancerous tissue could possibly be explored for differential diagnosis of benign and malignant thyroid nodules.

    Author Contributions
    Received 12 Jan 2022; Accepted 09 Feb 2022; Published 12 Feb 2022;

    Academic Editor: Qiping Dong, China

    Checked for plagiarism: Yes

    Review by: Single-blind

    Copyright ©  2022 Vladimir Zaichick

    License
    Creative Commons License     This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

    Competing interests

    The authors have declared that no competing interests exist.

    Citation:

    Vladimir Zaichick (2022) Content of Copper, Iron, Iodine, Rubidium, Strontium and Zinc in Thyroid Malignant Nodules and Thyroid Tissue adjacent to Nodules. Journal of Clinical and Diagnostic Pathology - 1(4):7-17.

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    DOI 10.14302/issn.2689-5773.jcdp-22-4065

    Introduction

    Thyroid malignant nodules (TMNs) are the most common endocrine cancer and the fifth most frequently occurring type of malignancies 1, 2, 3. The incidence of TMNs has increased worldwide over the past four decades. TMNs are divided into three main histological types: differentiated (papillary and follicular thyroid cancer), undifferentiated (poorly differentiated and anaplastic thyroid cancer, and medullary thyroid cancer, arising from C cells of thyroid 3. During the 20th century, there was the dominant opinion that TMNs is the simple consequence of iodine deficiency 4. However, it was found that TMNs is a frequent disease even in those countries and regions where the population is never exposed to iodine shortage. Moreover, it was shown that iodine excess has severe consequences on human health and associated with the presence of TMNs 5, 6, 7, 8. It was also demonstrated that besides the iodine deficiency and excess many other dietary, environmental, and occupational factors are associated with the TMNs incidence 9, 10, 11. Among these factors a disturbance of evolutionary stable input of many trace elements (TEs) in human body after industrial revolution plays a significant role in etiology of TMNs 12.

    Besides iodine, many other TEs have also essential physiological functions 13. Essential or toxic (goitrogenic, mutagenic, carcinogenic) properties of TEs depend on tissue-specific need or tolerance, respectively 13.Excessive accumulation or an imbalance of the TEs may disturb the cell functions and may result in cellular proliferation, degeneration, death, benign or malignant transformation 13, 14, 15.

    In our previous studies the complex of in vivo and in vitro nuclear analytical and related methods was developed and used for the investigation of iodine and other TEs contents in the normal and pathological thyroid 16, 17, 18, 19, 20, 21, 22. Iodine level in the normal thyroid was investigated in relation to age, gender and some non-thyroidal diseases 23, 24. After that, variations of many TEs content with age in the thyroid of males and females were studied and age- and gender-dependence of some TEs was observed 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41. Furthermore, a significant difference between some TEs contents in colloid goiter, thyroiditis, and thyroid adenoma in comparison with normal thyroid was demonstrated 42, 43, 44, 45, 46.

    To date, the etiology and pathogenesis of TMNs must be considered as multifactorial. The present study was performed to find out differences in TEs contents between the group of cancerous tissues, thyroid tissue adjacent to tumor, and “normal” thyroid (TEs as thyroid cancer biomarkers), as well as to clarify the role of some TEs in the etiology of TMNs. Having this in mind, the aim of this exploratory study was to examine differences in the content of copper (Cu), iron (Fe), iodine (I), rubidium (Rb), strontium (Sr), and zinc (Zn) in tumors and adjacent to tumor tissues of thyroids with TMNs, using a combination of non-destructive 109Cd and 241Am radionuclide-induced energy-dispersive X-ray fluorescent analysis, and to compare the levels of these TEs in two groups (tumor and adjacent to tumor tissues) of the cohort of TMNs samples. Moreover, for understanding a possible role of TEs in etiology and pathogenesis of TMNs, as well as thyroid cancer biomarkers, results of the study were compared with previously obtained data for the same TEs in “normal” thyroid tissue 42, 43, 44, 45, 46.

    Material and Methods

    All patients with TMNs (n=41, mean age M±SD was 46±15 years, range 16-75) were hospitalized in the Head and Neck Department of the Medical Radiological Research Centre (MRRC), Obninsk.. Thick-needle puncture biopsy of suspicious nodules of the thyroid was performed for every patient, to permit morphological study of thyroid tissue at these sites and to estimate their trace element contents. In all cases the diagnosis has been confirmed by clinical and morphological results obtained during studies of biopsy and resected materials. Histological conclusions for malignant tumors were: 25 papillary adenocarcinomas, 8 follicular adenocarcinomas, 7 solid carcinomas, and 1 reticulosarcoma. Tissue samples of tumor and visually intact tissue adjacent to tumor were taken from resected materials.

    “Normal” thyroids for the control group samples were removed at necropsy from 105 deceased (mean age 44±21 years, range 2-87), who had died suddenly. The majority of deaths were due to trauma. A histological examination in the control group was used to control the age norm conformity, as well as to confirm the absence of micro-nodules and latent cancer.

    All studies were approved by the Ethical Committees of MRRC. All the procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments, or with comparable ethical standards. Informed consent was obtained from all individual participants included in the study

    All tissue samples obtained from tumors and visually intact tissue adjacent to tumors were divided into two portions using a titanium scalpel to prevent contamination by TEs of stainless steel 47. One was used for morphological study while the other was intended for TEs analysis. After the samples intended for TEs analysis were weighed, they were freeze-dried and homogenized 48.

    To determine the contents of the TEs by comparison with known data for standard, aliquots of commercial, chemically pure compounds and synthetic reference materials were used 49. Ten subsamples of the Certified Reference Material (CRM) IAEA H-4 (animal muscle) were analyzed to estimate the precision and accuracy of results. The CRM IAEA H-4 subsamples were prepared in the same way as the samples of dry homogenized thyroid tissue.

    Details of the relevant facility for EDXRF determination of Cu, Fe, Rb, Sr, and Zn contents with 109Cd radionuclide source, methods of analysis and the quality control of results were presented in our earlier publications concerning the 109Cd-EDXRF analysis of human thyroid and prostate tissue 25, 26, 50, 51.

    Details of the relevant facility for EDXRF determination of I contents with 241Am radionuclide source, methods of analysis and the quality control of results were presented in our earlier publication concerning the 241Am-EDXRF analysis of human thyroid in norm and pathology 21.

    All thyroid samples for TEs analysis were prepared in duplicate, and mean values of TEs contents were used in final calculation. Using Microsoft Office Excel software, a summary of the statistics, including, arithmetic mean, standard deviation of mean, standard error of mean, minimum and maximum values, median, percentiles with 0.025 and 0.975 levels was calculated for TEs contents in nodular and adjacent tissue of thyroids with TMNs. Data for “normal” thyroid were taken from our previous publications 42, 43, 44, 45, 46. The difference in the results between three groups of samples (“normal”, “tumor”, and “adjacent”) was evaluated by the parametric Student’s t-test and non-parametric Wilcoxon-Mann-Whitney U-test.

    Results

    Table 1 presents certain statistical parameters (arithmetic mean, standard deviation, standard error of mean, minimal and maximal values, median, percentiles with 0.025 and 0.975 levels) of the Cu, Fe, I, Rb, Sr, and Zn mass fraction in “normal”, “tumor”, and “adjacent” groups of thyroid tissue samples.

    The ratios of means and the comparison of mean values of Cu, Fe, I, Rb, Sr, and Zn mass fractions in pairs of sample groups such as “normal” and “tumor”, “normal” and “adjacent”, and also “adjacent” and “tumor” are presented in Table 2, Table 3, and Table 4, respectively.

    Discussion

    As was shown before 21, 25, 26, 50, 51 good agreement of the Cu, Fe, I, Rb, Sr, and Zn contents in CRM IAEA H-4 samples analyzed by EDXRF with the certified data of this CRM indicates acceptable accuracy of the results obtained in the study of “normal”, “tumor”, and “adjacent” groups of thyroid tissue samples presented in Table 1, Table 2, Table 3, and Table 4

    From Table 2, it is observed that in cancerous tissue the mass fraction of I and Zn are 23 times and 25%, respectively, lower whereas mass fractions of Cu and Rb are 3.4 and 1.4 times, respectively, higher than in normal tissues of the thyroid. Thus, if we accept the TEs contents in thyroid glands in the “normal” group as a norm, we have to conclude that with a malignant transformation the Cu, I, Rb, and Zn in thyroid tissue significantly changed. In a general sense Cu, Fe, and Zn contents found in the “normal” and “adjacent” groups of thyroid tissue samples were very similar (Table 3,). However, in the “adjacent” group mean mass fractions of I and Rb were 1.75 and 2.06 times, respectively, higher, whereas mean value of Sr content 4 times lower than in the “normal” group. Significant changes of tumor TEs contents in comparison with thyroid tissue adjacent to tumor were found only for I (decrease) and Sr (increase). In malignant tumor Sr contents were approximately 5.4 times higher, while I content 40 times lower than in “adjacent” group of tissue samples (Table 4). Thus, from obtained results it was possible to conclude that the common characteristics of TMNs in comparison with “normal” thyroid and visually “intact” thyroid tissue adjacent to malignant tumors were drastically reduced level of I (Table 2, Table 4).

    Table 1. Some statistical parameters of Cu, Fe, I, Rb, Sr, and Zn mass fraction (mg/kg, dry mass basis) in normal thyroid and thyroid cancer (tumor and “intact” thyroid tissue adjacent to tumor)
    Tissue Element Mean SD SEM Min Max Median P 0.025 P 0.975
    Normal Cu 4.23 1.52 0.18 0.50 7.50 4.15 1.57 7.27
    thyroid Fe 222 102 11 47.1 512 204 65.7 458
      I 1618 1041 108 110 5150 1505 220 3939
      Rb 9.03 6.17 0.66 1.80 42.9 7.81 2.48 25.5
      Sr 4.55 3.22 0.37 0.10 13.7 3.70 0.48 12.3
      Zn 112 44.0 4.7 6.10 221 106 35.5 188
    Cancer Cu 14.5 9.4 2.6 4.00 32.6 10.9 4.21 31.4
    (tumor) Fe 238 184 30 54 893 176 55.0 680
      I 71.6 72.5 11.6 2.00 341 64.0 2.19 237
      Rb 12.4 5.00 0.79 4.80 27.4 11.5 4.90 20.0
      Sr 6.25 7.83 1.63 0.93 30.8 3.00 0.985 25.0
      Zn 84.3 57.4 9.2 36.7 277 65.3 39.0 273
    Cancer Cu 8.08 3.15 1.58 4.90 12.1 7.65 5.01 11.9
    (adjacent Fe 239 137 26 95.2 753 201 104 584
    tissue) I 2839 1335 240 587 6571 2652 827 5675
      Rb 18.6 16.7 3.2 5.00 67.0 12.0 5.72 65.6
      Sr 1.16 0.29 0.14 0.83 1.40 1.20 0.84 1.40
      Zn 109 55 11 20.4 272 109 29.1 213

    M – arithmetic mean, SD – standard deviation, SEM – standard error of mean, Min – minimum value, Max – maximum value, P 0.025 – percentile with 0.025 level, P 0.975 – percentile with 0.975 level.

     

    Table 2. Differences between mean values (M±SEM) of Cu, Fe, I, Rb, Sr, and Zn mass fraction (mg/kg, dry mass basis) in normal thyroid and thyroid cancer ((tumor)
    Element Thyroid tissue   Ratio
    Normalthyroid Cancer(tumor) Student’s t-testp£ U-testp Tumor/Normal
    Cu 4.23±0.18 14.5±2.6 0.0019 ≤0.01 3.43
    Fe 222±11 238±30 0.610 >0.05 1.07
    I 1618±108 71.6±11.6 0.00000000001 ≤0.01 0.044
    Rb 9.03±0.66 12.4±0.79 0.0013 ≤0.01 1.37
    Sr 4.55±0.37 6.25±1.63 0.319 >0.05 1.37
    Zn 112±5 84.3±9.2 0.0086 ≤0.01 0.75

    M – arithmetic mean, SEM – standard error of mean, Statistically significant values are in bold.

     

    Table 3. Differences between mean values (M±SEM) of Cu, Fe, I, Rb, Sr, and Zn mass fraction (mg/kg, dry mass basis) in normal thyroid and “intact” thyroid tissue adjacent to tumor
    Element Thyroid tissue   Ratio
    Normalthyroid Cancer(adjacent) Student’s t-testp£ U-testp Adjacent/Normal
    Cu 4.23±0.18 8.08±1.58 0.092 ≤0.05 1.91
    Fe 222±11 239±26 0.542 >0.05 1.08
    I 1618±108 2839±240 0.000033 ≤0.01 1.75
    Rb 9.03±0.66 18.6±3.2 0.0068 ≤0.01 2.06
    Sr 4.55±0.37 1.16±0.14 0.00000000001 ≤0.01 0.25
    Zn 112±5 109±11 0.778 >0.05 0.97

    M – arithmetic mean, SEM – standard error of mean, Statistically significant values are in bold.

     

    Table 4. Differences between mean values (M±SEM) of, Cu, Fe, I, Rb, Sr, and Zn mass fraction (mg/kg, dry mass basis) in thyroid cancer and “intact” thyroid tissue adjacent to tumor
    Element Thyroid tissue   Ratio
    Cancer (adjacent) Cancer (tumor) Student’s t-test p£ U-test p Adjacent/Tumor
    Cu 8.08±1.58 14.5±2.6 0.051 ≤0.05 1.79
    Fe 239±26 238±30 0.978 >0.05 1.00
    I 2839±240 71.6±11.6 0.00000000001 ≤0.01 0.025
    Rb 18.6±3.2 12.4±0.79 0.072 >0.05 0.67
    Sr 1.16±0.14 6.25±1.63 0.0051 ≤0.01 5.39
    Zn 109±11 84.3±9.2 0.083 >0.05 0.77

    M – arithmetic mean, SEM – standard error of mean, Statistically significant values are in bold.

     

    Characteristically, elevated or reduced levels of TEs observed in thyroid nodules are discussed in terms of their potential role in the initiation and promotion of these thyroid lesions. In other words, using the low or high levels of the TEs in affected thyroid tissues researchers try to determine the role of the deficiency or excess of each TE in the etiology and pathogenesis of thyroid diseases. In our opinion, abnormal levels of many TEs in TMNs could be and cause, and also effect of thyroid tissue transformation. From the results of such kind studies, it is not always possible to decide whether the measured decrease or increase in TEs level in pathologically altered tissue is the reason for alterations or vice versa. According to our opinion, investigation of TEs contents in thyroid tissue adjacent to malignant nodules and comparison obtained results with TEs levels typical of “normal” thyroid gland may give additional useful information on the topic because these data show conditions of tissue in which TMNs were originated and developed.

     

    Copper

    Cu is a ubiquitous element in the human body which plays many roles at different levels. Various Cu-enzymes (such as amine oxidase, ceruloplasmin, cytochrome-c oxidase, dopamine-monooxygenase, extracellular superoxide dismutase, lysyl oxidase, peptidylglycineamidating monoxygenase, Cu/Zn superoxide dismutase, and tyrosinase) mediate the effects of Cu deficiency or excess. Cu excess can have severe negative impacts. Cu generates oxygen radicals and many investigators have hypothesized that excess copper might cause cellular injury via an oxidative pathway, giving rise to enhanced lipid peroxidation, thiol oxidation, and, ultimately, DNA damage 52, 53, 54. Thus, Cu accumulation in thyroid parenchyma with age may be involved in oxidative stress, dwindling gland function, and increasing risk of goiter or cancer 25, 26, 31, 32, 33, 34. The significantly elevated level of Cu in thyroid malignant tumors and tissue adjacent to tumors, observed in the present study, supports this speculation. However, an overall comprehension of Cu homeostasis and physiology, which is not yet acquired, is mandatory to establish Cu exact role in the thyroid malignant tumors etiology and metabolism. Anyway, the accumulation of Cu in neoplastic thyroids could possibly be explored for diagnosis of TMNs.

    Iodine

    Nowadays it was well established that iodine deficiency or excess has severe consequences on human health and associated with the presence of TMNs 4, 5, 6, 7, 8, 55, 56, 57. In present study elevated level of I in thyroid tissue adjacent to malignant tumor and drastically reduced I mass fraction in cancerous tissue was found in comparison with “normal” thyroid.

    Compared to other soft tissues, the human thyroid gland has higher levels of I, because this element plays an important role in its normal functions, through the production of thyroid hormones (thyroxin and triiodothyronine) which are essential for cellular oxidation, growth, reproduction, and the activity of the central and autonomic nervous system. As was shown in present study, malignant transformation is accompanied by a significant loss of tissue-specific functional features, which leads to a drastically reduction in I content associated with functional characteristics of the human thyroid tissue. Because the malignant part of gland stopped to produce thyroid hormones, the rest “intact” part of thyroid tries to compensate thyroid hormones deficiency and work more intensive than usual. The intensive work may explain elevated level of I in thyroid tissue adjacent to malignant tumor.

    Drastically reduced level of I content in cancerous tissue could possibly be explored for differential diagnosis of benign and malignant thyroid nodules, because, as was found in our ealier studies, thyroid benign trasformation (goiter, thyroiditis, and adenoma) is accompanied by a little loss of I accumulation 42, 43, 44, 45, 46.

    Rubidium

    There is very little information about Rb effects on thyroid function. Rb as a monovalent cation Rb+ is transfered through membrane by the Na+K+-ATPase pump like K+ and concentrated in the intracellular space of cells. Thus, Rb seems to be more intensivly concentrated in the intracellular space of cells. The sourse of Rb elevated level in tumor and adjacent to tumor tissue may be Rb environment overload. The excessive Rb intake may result a replacement of medium potassium by Rb, which effects on iodide transport and iodoaminoacid synthesis by thyroid 58. The sourse of Rb increase in TMNs tissue may be not only the excessive intake of this TE in organism from the environment, but also changed Na+K+ -ATPase or H+K+ - ATPase pump membrane transport systems for monovalent cations, which can be stimulated by endocrin system, including thyroid hormones 59. It was found also that Rb has some function in immune responce 60 and that elevated concentration of Rb could modulate proliferative responses of the cell, as was shown for bone marrow leukocytes 61. These data partially clarify the possible role of Rb in etiology and pathogenesis of TMNs.

    Limitations

    This study has several limitations. Firstly, analytical techniques employed in this study measure only six TEs (Cu, Fe, I, Rb, Sr, and Zn) mass fractions. Future studies should be directed toward using other analytical methods which will extend the list of TEs investigated in “normal” thyroid and in pathologically altered tissue. Secondly, the sample size of TMNs group was relatively small and prevented investigations of TEs contents in this group using differentials like gender, histological types of TMNs, tumor functional activity, stage of disease, and dietary habits of patients with TMNs. Lastly, generalization of our results may be limited to Russian population. Despite these limitations, this study provides evidence on many TEs level alteration in malignant tumor and adjacent to tumor tissue and shows the necessity to continue TEs research of TMNs.

    Conclusion

    In this work, TEs analysis was carried out in the tissue samples of TMNs using EDXRF. It was shown that EDXRF with using 109Cd and 241Am radionuclide sources is an adequate analytical tool for the non-destructive determination of Cu, Fe, I, Rb, Sr, and Zn content in the tissue samples of human thyroid in norm and pathology, including needle-biopsy specimens. It was observed that in cancerous tissue the mass fraction of I and Zn were 23 times and 25%, respectively, lower whereas mass fractions of Cu and Rb were 3.4 and 1.4 times, respectively, higher than in normal tissues of the thyroid. In a general sense Cu, Fe, and Zn contents found in the “normal” and “adjacent” groups of thyroid tissue samples were very similar. However, in the “adjacent” group mean mass fractions of I and Rb were 1.75 and 2.06 times, respectively, higher, while mean value of Sr content was 4 times lower than in the “normal” group. In malignant tumor Sr contents were approximately 5.4 times higher, while I content 40 times lower than in “adjacent” group of tissue samples. Thus, from results obtained, it was possible to conclude that the common characteristics of TMNs in comparison with “normal” thyroid and visually “intact” thyroid tissue adjacent to nodules were drastically reduced level of I. It was supposed that the drastically reduced level of I content in cancerous tissue could possibly be explored for differential diagnosis of benign and malignant thyroid nodules.

    Funding

    There were no any sources of funding that have supported this work.

    Acknowledgements

    The author is extremely grateful to Profs. B.M. Vtyurin and V.S. Medvedev, Medical Radiological Research Center, Obninsk, as well as to Dr. Yu. Choporov, former Head of the Forensic Medicine Department of City Hospital, Obninsk, for supplying thyroid samples.

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