The isolation of thyroxine (T4), the discovery of 3,5,3'-triiodothyronine (T3), and the identification of the deiodinases that generate T3 from T4: An historical review

The Structure and Functional Changes of Thyroid in Severe Acute Pancreatitis Rats

Severe acute pancreatitis (SAP) is associated with metabolic disorders, hypocalcemia, and multiple organ failure. The objective of this study was to investigate changes in thyroid ultrastructure and function in rats with SAP and to provide a theoretical basis for the clinical treatment of thyroid injury in patients with SAP. 64 male SPF Wistar rats were randomly divided into the SAP group and the control group. Pancreatic enzymatic indicators and thyroid hormones were detected, pathology scores were evaluated, and morphological changes were observed under light microscopy and transmission electron microscopy (TEM) in both groups. The serum levels of triiodothyronine (T3), tetraiodothyronine (T4) and Ca2+ were significantly lower in the SAP group than in the control group (P<0.05), whereas the level of calcitonin (CT) was significantly higher than that in the control group (P<0.05). The thyroid structure (pathology and electron microscopy) of the SAP rats was seriously damaged and worsened over time. SAP can cause thyroid injury through a variety of mechanisms, which can also retroact to pancreatitis to aggravate the inflammatory response. This study may have theoretical significance for basic research on SAP. Key words Severe acute pancreatitis, Thyroid, Structure and functional changes, Transmission electron microscopy.

Development of an animal model of hypothyroxinemia during pregnancy in Wistar rats

BACKGROUND

Hypothyroxinemia is a subclinical thyroid hormone deficiency in which the mother has inadequate levels of T4 during pregnancy. The fetus relies entirely on the mother's T4 hormone level for early neurodevelopment. Isolated maternal hypothyroxinemia (IMH) in the first trimester of pregnancy can lead to lower intelligence, lower motor scores, and a higher risk of mental illness in descendants. Here, we focus on the autism-like behavior of IMH offspring.

METHODS

The animals were administered 1 ppm of propylthiouracil (PTU) for 9 weeks. Then, the concentrations of T3, T4, and thyroid-stimulating hormone (TSH) were detected using enzyme-linked immunosorbent assay (ELISA) to verify the developed animal model of IMH. We performed four behavioral experiments, including the marble burying test, open-field test, three-chamber sociability test, and Morris water maze, to explore the autistic-like behavior of 40-day-old offspring rats.

RESULTS

The ELISA test showed that the serum T3 and TSH concentrations in the model group were normal compared with the negative control group, whereas the T4 concentration decreased. In the behavioral experiments, the number of hidden marbles in the offspring of IMH increased significantly, the frequency of entering the central compartment decreased, and the social ratio decreased significantly.

CONCLUSION

The animal model of IMH was developed by the administration of 1 ppm of PTU for 9 weeks, and there were autistic-like behavior changes such as anxiety, weakened social ability, and repeated stereotyping in the IMH offspring by 40 days.

Thyroid metabolism and supplementation. A review framed in sports environment

OBJECTIVES

This paper aimed to consider those features that may suggest a link between thyroid hormones pharmacology and athletes' health based on current consumption trends in a population of athletes.

METHODS

Methods used were observation, description, and synthesis, mainly. Among the documents reviewed were: books, scientific articles, and review articles peer-reviewed. The review covered sources published in the period 1961 to 2021. Only references with a traceable origin were accepted (DOI numbering, ISSN and ISBN, as well as peer-reviewed journals). The data on the consumption of thyroid hormones derivatives were extracted from the Doping Control Forms of athlete samples received at Laboratorio Antidoping FMSI of Rome from 2017 to 2021.

RESULTS

An overview of the biosynthesis, pharmacology, and metabolism of thyroid hormones, including thyronamines and thyronacetic acids, was presented. Likewise, a summary is presented on the relationship between thyroid hormones and ethnic and gender differences, their physiology in sport, and the reasons why their use could be considered attractive for athletes.

CONCLUSION

Today, thyroid hormones are not listed as a prohibited substance by the World Anti-Doping Agency. However, several requests to include levothyroxine on the prohibited list are documented. The observation that the number of athletes taking thyroid hormones is growing, particularly in sports such as cycling, triathlons, and skating, should prompt an update on this topic.

The Role of Thyroid Hormones in the Differential Diagnosis of Tuberculous and Parapneumonic Pleural Effusions

BACKGROUND

The differential diagnosis of tuberculous pleural effusion (TPE) and parapneumonic pleural effusion (PPE) is challenging due to similar clinical manifestations and body fluid biochemical profiles. Thyroid hormone levels change in response to lymphocyte proliferation in the peripheral blood of patients with mycobacterial infections such as tuberculosis; therefore, this study aimed to investigate the utility of assessing thyroid hormone levels to aid in the differential diagnosis of TPE and PPE.

METHODS

We measured free triiodothyronine (FT3), free thyroxine (FT4), and thyroid-stimulating hormone (TSH) levels in the pleural effusions of 59 newly admitted patients (32 and 27 with TPE and PPE, respectively). Hormone levels were assessed using an electrochemiluminescence technique, and the diagnostic parameters for tuberculosis were evaluated. Differences in hormone levels between patients with TPE and PPE were assessed by t-tests, and their diagnostic value for a differential diagnosis was evaluated by receiver operating characteristic curve analyses.

RESULTS

FT3 and FT4 levels in patients with TPE were significantly higher than those in patients with PPE (p < 0.01 and p < 0.05, respectively), whereas TSH expression did not significantly differ between the two groups (p > 0.05). FT3 and FT4 levels showed no correlation with sex or history of smoking, although FT3 levels decreased with age. The highest sensitivity was observed for the quantification of FT3 levels (84.38%).

CONCLUSIONS

Increased FT3 and FT4 levels could potentially be used for the differential diagnosis of TPE and PPE.

The Role of Thyroid Function in Alzheimer's Disease

The thyroid gland is crucial for the regulation of metabolism, growth, and development of various tissues, organs, systems, including the central nervous system. Recent studies have implicated the role of thyroid dysfunction in the etiology of Alzheimer's disease (AD), while AD leads to a significant increase in the prevalence of thyroid dysfunction. In this review, we have analyzed the role of thyroid function in the pathophysiology of AD as well as its biomarkers. The present review aims to provide encouraging targets for early screening of AD risk factors and intervention strategies.

Genomic and Non-Genomic Mechanisms of Action of Thyroid Hormones and Their Catabolite 3,5-Diiodo-L-Thyronine in Mammals

Since the realization that the cellular homologs of a gene found in the retrovirus that contributes to erythroblastosis in birds (v-erbA), i.e. the proto-oncogene c-erbA encodes the nuclear receptors for thyroid hormones (THs), most of the interest for THs focalized on their ability to control gene transcription. It was found, indeed, that, by regulating gene expression in many tissues, these hormones could mediate critical events both in development and in adult organisms. Among their effects, much attention was given to their ability to increase energy expenditure, and they were early proposed as anti-obesity drugs. However, their clinical use has been strongly challenged by the concomitant onset of toxic effects, especially on the heart. Notably, it has been clearly demonstrated that, besides their direct action on transcription (genomic effects), THs also have non-genomic effects, mediated by cell membrane and/or mitochondrial binding sites, and sometimes triggered by their endogenous catabolites. Among these latter molecules, 3,5-diiodo-L-thyronine (3,5-T2) has been attracting increasing interest because some of its metabolic effects are similar to those induced by T3, but it seems to be safer. The main target of 3,5-T2 appears to be the mitochondria, and it has been hypothesized that, by acting mainly on mitochondrial function and oxidative stress, 3,5-T2 might prevent and revert tissue damages and hepatic steatosis induced by a hyper-lipid diet, while concomitantly reducing the circulating levels of low density lipoproteins (LDL) and triglycerides. Besides a summary concerning general metabolism of THs, as well as their genomic and non-genomic effects, herein we will discuss resistance to THs and the possible mechanisms of action of 3,5-T2, also in relation to its possible clinical use as a drug.