Plasma Thyroid Hormone Levels Research Articles

Per- and Polyfluoroalkyl Substances in the Duluth, Minnesota Area: Exposure to and Biomarker Responses in Tree Swallows Relative to Known Fire-Fighting Foam Sources.

Tree swallow nest boxes were deployed at sites proximal to two putative aqueous film forming foam (AFFF) sources in the Duluth, MN area, as well as along the St. Louis River and a reference lake for comparative purposes in 2019, 2020 and 2021. The two AFFF sites were the current Duluth Air National Guard Base (ANG) and the Lake Superior College Emergency Response Training Center. Between 13 and 40 per- and polyfluoroalkyl substances (PFAS), depending on year, were detected and quantified in tree swallow egg, nestling carcasses, and stomach contents. Assessments were made of oxidative stress and ethoxyresorufin-O-dealkylase activity in liver tissue, thyroid hormone levels in plasma and thyroid glands, DNA damage in red blood cells, and two measures of immune response (haptoglobin-like activity and immunoglobulin) in plasma of the nestlings. Additionally, other contaminants, such as polychlorinated biphenyls, legacy organochlorine pesticides, and trace elements, were assessed at sites with no previous data. Total egg PFAS concentrations at the ANG site and north of that site were 30-40 times higher than at the reference lake, while nestling PFAS concentrations were 10-15 times higher. In contrast, the St. Louis River sites had slightly, but non-statistically significant, elevated egg and nestling PFAS concentrations relative to the reference lake (2-5 times higher). One PFAS, perfluorohexane sulfonate (PFHxS), was higher, as a proportion of total PFAS, at sites with a known AFFF source compared to the reference lake, as well as compared to sites along the St. Louis River with mainly urban and industrial sources of PFAS. The ratio of total carboxylates to total sulfonates also distinguished between PFAS sources. There were few to no differences in biomarker responses among sites, and no association with PFAS exposure.

Optimized methods for measuring competitive binding of chemical substances to thyroid hormone distributor proteins transthyretin and thyroxine binding globulin

Transthyretin (TTR) and thyroxine-binding globulin (TBG) are two major thyroid hormone (TH) distributor proteins in human plasma, playing important roles in stabilizing the TH levels in plasma, delivery of TH to target tissues, and trans-barrier transport. Binding of xenobiotics to these distributor proteins can potentially affect all these three important roles of distributor proteins. Therefore, fast and cost-effective experimental methods are required for both TTR and TBG to screen both existing and new chemicals for their potential binding. In the present study, the TTR-binding assay was therefore simplified, optimized and pre-validated, while a new TBG-binding assay was developed based on fluorescence polarization as a readout. Seven model compounds (including positive and negative controls) were tested in the pre-validation study of the optimized TTR-binding assay and in the newly developed TBG-binding assay. The dissociation constants of the natural ligand (thyroxine, T4) and potential competitors were determined and compared between two distributor proteins, showing striking differences for perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA).

Magnitude and time course of urinary iodine excretion in patients after amiodarone therapy.

Amiodarone is a source of iodine excess that may persist in the body for long time after its withdrawal. The aim of the present analysis was to evaluate the magnitude and long-term time course of 24-h urinary iodine (UI) excretion in patients on antiarrhythmic therapy with amiodarone. 24-h UI excretion and thyroid function were evaluated in 67 patients on amiodarone therapy. All patients were clinically and biochemically euthyroid before starting treatment and were followed-up by 6-month measurements of 24-h UI excretion and plasma thyroid hormones levels. Upon amiodarone withdrawal, normal range of UI was achieved after a mean time of 15.2±7.7 months. Since amiodarone initiation, 20 patients developed thyroid dysfunction. No differences were observed in terms of treatment length or median UI levels between patients remaining euthyroid and those developing thyroid dysfunction: median UI in the euthyroid group was 8094 µg/24 h (Interquartile Range [IQR]: 4082-10766) vs. 10851 µg/24 h (IQR: 8529-12804) in the thyroid dysfunction group at 6 months (P=0.176) and 8651 µg/24 h (IQR: 6924-11574) vs. 8551 µg/24 h (IQR: 4916-13580) at one year from amiodarone initiation (P=0.886). The occurrence of thyroid dysfunction was equally distributed among patients taking amiodarone for more than one year versus those under treatment for less than one year. These results confirm the long-lasting total-body iodine stores and consequent excretion in patients after amiodarone withdrawal. These long-lasting iodine stores might be taken into special account in patients necessitating therapy with radioactive iodine and for long-term monitoring of thyroid function after amiodarone discontinuation.

Plasma Thyroid Hormone Concentration is Associated with Hepatic Triglyceride Content in Patients with Type 2 Diabetes

This cross-sectional study investigated the association between plasma thyroid hormone levels and hepatic triglyceride content in 150 patients with type 2 diabetes. Our findings revealed a significant negative correlation between plasma triiodothyronine (T3) levels and hepatic triglyceride content, suggesting a protective metabolic role of T3. No significant correlations were observed with thyroxine (T4) or thyroid-stimulating hormone (TSH). The study underscores the potential of T3 as a modulator of hepatic lipid metabolism in diabetic patients, highlighting its relevance in managing hepatic complications associated with diabetes. Further research is necessary to confirm these findings and explore therapeutic implications. Keywords: Thyroid Hormones, Hepatic Triglyceride, Type 2 Diabetes, Triiodothyronine (T3)

Association between low-normal thyroid function and advanced liver fibrosis in metabolic dysfunction-associated fatty liver disease patients: a retrospective cohort study.

Recent studies have found that thyroid function may be associated with the occurrence and development of advanced liver fibrosis in patients with metabolic dysfunction-associated fatty liver disease (MAFLD). However, the majority of such research has consisted of cross-sectional studies. This retrospective cohort study aimed to investigate the effect of low-normal thyroid function on advanced liver fibrosis in MAFLD patients over a 5-year period. This retrospective cohort study enrolled 825 outpatients and inpatients with MAFLD who attended the Third Affiliated Hospital of Sun Yat-sen University (Guangzhou, China) between January 2011 and December 2018. Based on plasma thyroid hormone and thyroid-stimulating hormone levels, these patients were divided into two groups, namely a low-normal thyroid function group and a strict-normal thyroid function group. The fibrosis-4 score was used to assess advanced liver fibrosis. A chi-square test was conducted to compare the occurrence of advanced fibrosis between the groups. Among the 825 MAFLD patients, 117 and 708 were defined as having low-normal thyroid function and strict-normal thyroid function, respectively. Follow-up data were available for 767 patients (93.0%) during a 5-year period. Eight (7.5%) MAFLD patients with low-normal thyroid function and 26 (3.9%) with strict-normal thyroid function developed advanced liver fibrosis and the cumulative incidence was not significantly different (P = 0.163). Stratification analysis showed that the lean MAFLD patients (body mass index ≤ 23 kg/m2) with low-normal thyroid function had a higher risk of advanced liver fibrosis than the lean MAFLD patients with strict-normal thyroid function (P < 0.05). Low-normal thyroid function is associated with advanced liver fibrosis among lean MAFLD patients.

Thyroid hormone manipulation influences development of endothermy and hatching in white leghorn chickens (Gallus gallus)

Chickens experience rapid change in their physiology and metabolism during hatching. We propose that thyroid hormones play a major role in regulating the developmental changes associated with attaining endothermy. To better understand the role thyroid hormones play in hatch timing and development of thermogenic capacity and metabolic rate we manipulated plasma thyroid hormone levels in chicken embryos beginning at 80% development (day 17 of a 21-day incubation) with either a single dose of triiodo-L-thyronine (T3) or the thyroperoxidase inhibitor methimazole (MMI). Manipulation of thyroid hormones altered the timing of hatching, accelerating hatching under hyperthyroid conditions, and prolonging hatching with hypothyroid conditions. Effect sizes comparisons of morphological variables between treatment groups revealed larger heart and body masses in hyperthyroid 1-day post hatch animals. Thyroid hormone manipulation influenced the thermal neutral zone for O2 consumption and body temperature during gradual cooling from 35 to 15 °C of externally pipped embryos and 1-day post hatch chicks. Hyperthyroid EP animals had a wider thermal neutral zone during cooling when compared to control animals. At the temperatures tested, the hypothyroid animals did not exhibit a thermal neutral zone. Similar differences between treatments in the breadth of the thermal neutral zone carried through to 1-day post hatch chickens. These findings suggest that thyroid manipulations influence the timing and development of the animal’s thermogenic response to cooling.

Divergent Thyroid Hormone Levels in Plasma and Left Ventricle of the Heart in Compensated and Decompensated Cardiac Hypertrophy Induced by Chronic Adrenergic Stimulation in Mice.

Chronic hemodynamic overload of the heart induces ventricular hypertrophy that may be either compensatory or progress to decompensation and heart failure. The gradual impairment of ventricular function is, at least in part, the result of a reduction of cardiac thyroid-hormone (TH) action. Here, we examined the proposed roles of increased cardiac expression of the TH-inactivating enzyme deiodinase type 3 (D3) and reduced plasma TH levels in diminishing cardiac TH levels. Using minipumps, mice were infused for one and two weeks with isoproterenol (ISO) alone or in combination with phenylephrine (PE). Remodeling of the heart induced by these adrenergic agonists was assessed by echocardiography. Left ventricular (LV) tissue and plasma TH levels (T4 and T3) were determined using liquid chromatography-tandem mass spectrometry. LV D3 activity was determined by conversion of radiolabeled substrate and quantification following HPLC. The results show that ISO induced compensated LV hypertrophy with maintained cardiac output. Plasma levels of T4 and T3 remained normal, but LV hormone levels were reduced by approximately 30% after two weeks, while LV D3 activity was not significantly increased. ISO + PE induced decompensated LV hypertrophy with diminished cardiac output. Plasma levels of T4 and T3 were substantially reduced after one and two weeks, together with a more than 50% reduction of hormone levels in the LV. D3 activity was increased after one week and returned to control levels after two weeks. These data show for the first time that relative to controls, decompensated LV hypertrophy with diminished cardiac output is associated with a greater reduction of cardiac TH levels than compensated hypertrophy with maintained cardiac output. LV D3 activity is unlikely to account for these reductions after two weeks in either condition. Whereas the mechanism of the mild reduction in compensated hypertrophy is unclear, changes in systemic TH homeostasis appear to determine the marked drop in LV TH levels and associated impairment of ventricular function in decompensated hypertrophy.

Plasma T3 and T4 Hormone Levels as Reference Values in Rehabilitated Common Buzzard (Buteo buteo), Long-Legged Buzzard (Buteo rufinus) and Golden Eagle (Aquila chrysaetos)

Applying appropriate criteria for raptors at rehabilitation stages including release and post release determines how healthy the animal can survive in its natural habitat for any length of time. In determining release criteria, clinical examinations of animals as well as clinical data should be evaluated. In this study, plasma T3 and T4 levels of 16 Common Buzzard (Buteo buteo), 7 Long-legged Buzzard (Buteo rufinus) and 7 Golden Eagles (Aquila chrysaetos) were determined at Kafkas University/ Kafkas Wildlife Conservation, Rescue, Rehabilitation Practice and Research Center between 2016-2018. All raptors were kept at the rehabilitation center for 1-3 months in bird care rooms and flight tunnels specially arranged for each species. Rehabilitated birds blood were collected before released to wild. Plasma T3 and T4 hormone levels were analysed and determined in raptors that considered suitable for release. Although small differences were detected between T3 and T4 values as a result of the analysis, no statistical difference was found. These small differences in values may be due to the metabolic responses and environmental conditions of each raptor. As a result, these plasma thyroid hormone levels in rehabilitated raptors can be accepted as reference values.

TOXIC EFFECTS OF AROCLOR 1254 ON RAT HEART AND THYROID AND MODIFYING ROLE OF SELENIUM STATUS

Objective: Polychlorinated biphenyls (PCBs) were very widely used in industrial products in past. These chemicals were banned in the 1970s due to their toxic effects. PCBs can still affect human health, as they are persistent in the environment. Aroclor 1254 (A1254) is a commercial PCB congener which was used in electrical transformers, fluorescent lighting fixtures and old appliances such as televisions or refrigerators. In this study, we aimed to evaluate the toxic effects of A1254 on heart and thyroid in male Sprague-Dawley rats. In addition, the modifying role of selenium status was also evaluated.&#x0D; Material and Method: 8-week-old male Sprague-Dawley (SD) rats were used in the experiment. The animals were separated randomly into 6 groups (n=6) as control; selenium supplemented (SeS); selenium deficient (SeD); A1254 exposed (A); selenium supplemented A1254 exposed (ASeS) and selenium deficient A1254 exposed (ASeD). A1254 was applied by gavage during the last 15 days of feeding period. Heart and thyroid weights and relative weights, plasma thyroid hormone levels, as well as thyroid and heart tissue oxidative/antioxidative parameters were evaluated.&#x0D; Result and Discussion: Results showed that A1254 exposure and selenium deficiency caused oxidative stress on both heart and thyroid. Plasma fT3 and fT4 levels markedly changed in ASeD group. In conclusion, it can be stated that A1254 exposure can cause lead to oxidative/antioxidative imbalance in both thyroid and heart and can disrupt functioning of thyroid hormones. Selenium seems to have a modifying role in A1254 toxicity in both organs, the importance of which should be evaluated with further mechanistic experiments.

Manipulating plasma thyroid hormone levels alters development of endothermy and ventilation in nestling red-winged blackbirds.

Thyroid hormones are key regulators of development and metabolism in vertebrates. During the nestling period, young of altricial species transition from an ectothermic phenotype to an endothermic phenotype. Red-winged blackbirds are an altricial species that exhibit an increase in plasma 3,3', 5-triiodo-L-thyronine (T3) levels during the first 5days post-hatch (dph), begin to develop endothermic metabolic responses by 7 dph, and fledge within 10 days of hatching. We propose that thyroid hormones play an important role in regulating development of endothermy during the nestling period in altricial birds. To better understand the effects of thyroid hormones on endothermic metabolic development in an altricial species, we treated nestling red-winged blackbirds on 2, 3, and 5 dph with either methimazole (MMI) to induce hypothyroidism or supplemental T3 to induce hyperthyroidism. We then measured on 5, 7, and 9 dph morphology and whole animal O2 consumption ( ) and ventilation in the thermal neutral zone and during gradual cooling. Treatment of nestlings with MMI resulted in lower plasma T3 levels on 5 dph that recovered by 7 dph, while supplementing with T3 did not affect plasma T3 levels on 5, 7 and 9 dph. Treatment with MMI resulted in smaller nestlings with smaller hearts and structural characters such as wing chord and femur length, but larger lungs and kidneys. Treatment with T3 produced smaller nestlings with smaller body masses and shorter femur and tarsus lengths. The development of and ventilation endothermic responses to gradual cooling in MMI treated nestlings were delayed when compared with control nestlings. In 9 dph nestlings, hypothyroidism resulted in alterations in the responses of ventilation frequency and tidal volume to cooling when compared with the control nestlings. Supplemental T3 had no effect on the development of and ventilation in the thermal neutral zone or in response to cooling. Our data suggest plasma thyroid hormone levels play an active role in the systemic development of endothermic capacity and the development of ventilatory control. In the nestling avian, multiple systems develop in concert to produce an endothermic phenotype, but reduced thyroid hormone delays maturation of endothermic capacity.

Development and metamorphosis in frogs deficient in the thyroid hormone transporter MCT8

Precisely regulated thyroid hormone (TH) signaling within tissues during frog metamorphosis gives rise to the organism-wide coordination of developmental events among organs required for survival. This TH signaling is controlled by multiple cellular mechanisms, including TH transport across the plasma membrane. A highly specific TH transporter has been identified, namely monocarboxylate transporter 8 (MCT8), which facilitates uptake and efflux of TH and is differentially and dynamically expressed among tissues during metamorphosis. We hypothesized that loss of MCT8 would alter tissue sensitivity to TH and affect the timing of tissue transformation. To address this, we used CRISPR/Cas9 to introduce frameshift mutations inslc16a2, the gene encoding MCT8, inXenopus laevis. We produced homozygous mutant tadpoles with a 29-bp mutation in the l-chromosome and a 20-bp mutation in the S-chromosome. We found that MCT8 mutants survive metamorphosis with normal growth and development of external morphology throughout the larval period. Consistent with this result, the expression of the pituitary hormone regulating TH plasma levels (tshb) was similar among genotypes as was TH response gene expression in brain at metamorphic climax. Further, delayed initiation of limb outgrowth during natural metamorphosis and reduced hindlimb and tail TH sensitivity were not observed in MCT8 mutants. In sum, we did not observe an effect on TH-dependent development in MCT8 mutants, suggesting compensatory TH transport occurs in tadpole tissues, as seen in most tissues in all model organisms examined.

Transplantable human thyroid organoids generated from embryonic stem cells to rescue hypothyroidism

The thyroid gland captures iodide in order to synthesize hormones that act on almost all tissues and are essential for normal growth and metabolism. Low plasma levels of thyroid hormones lead to hypothyroidism, which is one of the most common disorder in humans and is not always satisfactorily treated by lifelong hormone replacement. Therefore, in addition to the lack of in vitro tractable models to study human thyroid development, differentiation and maturation, functional human thyroid organoids could pave the way to explore new therapeutic approaches. Here we report the generation of transplantable thyroid organoids derived from human embryonic stem cells capable of restoring plasma thyroid hormone in athyreotic mice as a proof of concept for future therapeutic development.

Relationship between the development of hyperlipidemia in hypothyroidism patients.

As shown in the previous studies, hypothyroidism (HT) is identified to be closely associated with the elevated plasma levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), and with the decreased plasma levels of high density lipoprotein cholesterol (HDL-C). On the other hand, the thyroid hormone (TH), which has been considered as a vital hormone produced and released by the thyroid gland, are well-established to regulate the metabolism of plasma TC; whereas other evidence proposed that the thyroid-stimulating hormone (TSH) also regulated the plasma cholesterol metabolism independently of the TH, which further promotes the progression of hyperlipidemia. Nevertheless, the potential mechanism is still not illustrated. It is worth noting that several studies has found that the progression of HT-induced hyperlipidemia might be associated with the down-regulated plasma levels of TH and the up-regulated plasma levels of TSH, revealing that HT could promote hyperlipidemia and its related cardio-metabolic disorders. Otherwise, multiple novel identified plasma proteins, such as proprotein convertase subtilisin/kexin type 9 (PCSK9), angiopoietin-like protein (ANGPTLs), and fibroblast growth factors (FGFs), have also been demonstrated to embrace a vital function in modulating the progression of hyperlipidemia induced by HT. In the present comprehensive review, the recent findings which elucidated the association of HT and the progression of hyperlipidemia were summarized. Furthermore, other results which illustrated the underlying mechanisms by which HT facilitates the progression of hyperlipidemia and its cardio-metabolic disorders are also listed in the current review.

Menorrhagia as main presentation sign of severe hypothyroidism in a pediatric patient: a case report

BackgroundThe relative high frequency of menstrual irregularities in the first two–three years after menarche may lead to the risk of underestimation of associated pathological conditions, which are always to be accurately researched with careful examination and anamnesis. The association between menstrual irregularities and hypothyroidism is described in literature but the available data are scarce and mainly based on adult case series. It is described that low plasma levels of thyroid hormone can shift the hemostatic system towards a hypocoagulable and hyperfibrinolytic state and seem to lead to an increased bleeding risk.Case presentationThis case report describes the case of a thirteen years old girl who presented to our Emergency Department complaining of menorrhagia for the last fifteen days, leading to severe anemia. The objective examination revealed clinical signs of hypothyroidism and a severe short stature, lower than mid-parental height, with stunting of growth and a significant bone age delay. Blood exams and thyroid ultrasound were consistent with the diagnosis of severe hypothyroidism in autoimmune thyroiditis with acquired von Willebrand syndrome, growth hormone deficiency. Magnetic resonance showed pituitary functional hyperplasia.The substitutive therapy with levothyroxine led to the resolution of heavy bleeding after five days and following normalization of coagulative parameters and pituitary hyperplasia.ConclusionsHypothyroidism usually presents with unspecific symptoms, with consequent risk of diagnostic delay. It can influence the coagulation system and it seems to be associated to increased risk of menstrual irregularities.We underline the importance of a regular follow up of the pubertal development, including height measurements, thyroid palpation and menstrual anamnesis to intercept red flags findings for hypothyroidism.

The effectiveness of human chorionic gonadotropin in stimulation of second spermiation in pikeperch Sander lucioperca during the spawning season

The aim of the present study was to evaluate the effectiveness of human chorionic gonadotropin (hCG) in stimulation of second spermiation in already reproduced pikeperch males during the same spawning season. Fish (mean weight 919.9 ± 236.9 g) were divided into the control saline-injected group, and two groups injected with 200 and 400 IU hCG/kg body weight. Forty-eight hours following injection (at a temperature of 16.7 °C) the percentage of fish producing useable amounts of semen increased from 30% in the control group up to 80% in the treated fish and the highest volume of semen was recorded in fish treated with 400 IU/kg BW hCG. Spermatocrit (50.7 ± 9.1%) and sperm concentration (17.5 ± 5.0 × 109 spermatozoa/mL) were significantly higher in control fish than those recorded in hCG-treated fish (24.8 ± 7.7% and 8.1 ± 2.4 × 109 spermatozoa/mL in 200 IU/kg; 32.3 ± 17.6% and 10.9 ± 7.5 × 109 spermatozoa/mL in 400 IU/kg). No significant differences were observed between the groups with respect to sperm motility (as a spermatozoa activity time and percentage); however, a change in plasma alkaline phosphatase activity was found in the group injected with 400 IU/kg of hCG. The lack of significant differences in plasma metabolites and cortisol between control and hCG-treated fish indicated that the hCG had no effect on the stress response. Testosterone levels were significantly increased in the hCG-treated fish, whereas no significant differences in 17β-estradiol were recorded. No differences between the groups in plasma levels of thyroid hormones suggested lack of hCG-induced effect on hypothalamus-pituitary-thyroid axis. The results of this study demonstrated that the spermiation of already reproduced pikeperch males could be induced by hCG during the same spawning season. Based on the results on semen volume and concentration, injection with hCG could improve the efficiency of pikeperch reproduction to reduce the number of brooders and costs of juvenile pikeperch production.

Simulation of the plasma level of thyroid hormones for a total thyroidectomized virtual-patient treated by BMI and BSA-based LT4 monotherapy dose regimen

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Thyrotropic effects of balneotherapy in Truskavets’ spa and their endocrine, vegetative and metabolic accompaniments

Background. Previous studies of the Truskavetsian Scientific School of Balneology have studied the effects of course use of bioactive water Naftussya - the main therapeutic factor of the spa - on plasma levels of thyroid hormones in males and females healthy rats and women with thyroid hyperplasia. In men with chronic cholecystitis, the immediate thyrotropic effects of a single use of Naftussya water have been studied. The aim of this study is thyrotropic effects of balneotherapy in Truskavets’ spa and their endocrine, vegetative and metabolic accompaniments in men and women with chronic cholecystitis and pyelonephritis. Materials and Methods. The object of clinical-physiological observation were 34 men (23-70 years) and 10 women (39-76 years), who underwent rehabilitation treatment of chronic cholecystitis and pyelonephritis in remission in the Truskavets’ spa. The examination was performed twice, before and after a 7-10-day course of balneotherapy. The main object of study was the plasma level of Triiodothyronine. We determined also content in plasma Cortisol, Aldosterone, Testosterone and Calcitonin as well as the parameters of the HRV and metabolism. Results. We find in 16 patients (12 men and 4 women) inhibitory thyrotropic effect, in 22 (16 men and 6 women) neutral, and in 6 men only – enhancing effect of balneotherapy. Each variant of the thyrotropic effect is accompanied by characteristic changes in testosteronemia, calcitoninemia, parathyroid activity, Heart Rate, Baevskiy’s Activity Regulatory Systems Index, HRV-markers of vagal tone, Calciemia as well as VLD and LD lipoproteins Cholesterol plasma. Conclusion. Our data confirmed and supplemented the provisions on the multivariate effects of balneotherapy in the spa of Truskavets’ on the endocrine and autonomic nervous systems and metabolism of patients.

MINERAL DENSITY AND PROCESSES OF BONE TISSUE REMODELING IN CHILD POPULATION LIVING IN IODINE-DEFICIENT BIOGEOCHEMICAL TERRITORY

The territory of the Republic of Bashkortostan belongs to the regions with natural iodine deficiency in soil and water. The population of the republic is at risk of developing iodine deficiency conditions. The aim of the study was to evaluate the frequency of a decrease in bone mineral density and the level of markers of osteoresorption and bone formation in young schoolchildren and adolescents living in a region with natural iodine deficiency. Materials and methods. The survey covered 288 students of general education schools aged 11–12 and 309 students aged 14–15. Theauthors studiedconcentration of iodine in urine, plasma levels of thyroid hormones (thyroid stimulating hormone, free thyroxine), levels of calcium, magnesium, phosphorus, C-terminal telopeptides of type I collagen, activity of the bone isoenzyme of alkaline phosphatase. The volume of the thyroid gland, the mineral density of the bone tissue of the middle diaphysis of the tibia, the lower third of the radius were determined by ultrasonometry. Results and discussion. It was found that children have a high prevalence of iodine deficiency from 44% to 57.6% and a decrease in the concentration of iodine in the urine, an increase in the content of thyrotropin, calcium and magnesium in the blood plasma. Insufficient iodine supply leads to a slowdown in the intensity and imbalance of remodeling with a decrease in bone formation processes.

Seasonal Changes in Plasma Hormones, Sex-Related Genes Transcription in Brain, Liver and Ovary during Gonadal Development in Female Rainbow Trout (Oncorhynchus mykiss)

The purpose of this study was to investigate the periodic seasonal changes in endocrine activity and gonadal development of female rainbow trout (Oncorhynchus mykiss) in a high-altitude cold-water environment. The fish were sampled monthly from January to November and the levels of plasma hormones (estradiol (E2), cortisol and thyroid hormones (THS)) and vitellogenin (VTG) were measured by ELISA. Moreover, the transcriptions of sex-related genes in the ovary, brain, and liver were detected by qRT-PCR. The results showed a seasonal fluctuation of plasma hormones and VTG together with the development of the ovary, which reached a peak from August to October. Similarly, the transcription of hypothalamic gonadotropin-releasing hormone-2 (cgnrh-2), hypothalamic gonadotropin-releasing hormone receptors (gnrhr) and follicle-stimulating hormone (fsh) in the brain varied from January to September, but the highest level was detected in September to November. In addition, the transcription of sex-related genes located in the ovary and liver increased significantly during August to October, accompanied by a continuous increase in the gonadosomatic index (GSI) and a decrease in the hepatosomatic index (HSI). Therefore, plasma hormones and sex-related genes regulate the development and maturation of O. mykiss oocytes with the change in seasons and peaked in November. The results of this study provide a reference for improving the efficiency of the artificial reproduction of O. mykiss.

Chrysin restores memory deficit in hypothyroidism mice: Behavioral, neurochemical and computational approaches involving the neurotrophinergic system

Hypothyroidism is a condition that affects multiple systems, including the central nervous system, causing, for example, cognitive deficits closely related to Alzheimer's disease. The flavonoid chrysin is a natural compound associated with neuronal improvement in several experimental models. Here, we evaluated the effect of chrysin on cognitive impairment in hypothyroid female mice by exploring neuroplasticity. Hypothyroidism was induced by continuous exposure to 0.1% methimazole (MTZ) in drinking water for 31 days. On the 32nd day, the animals showed low plasma levels of thyroid hormones (hypothyroid mice) than the control group (euthyroid mice). Subsequently, mice were intragastrically administered with vehicle or chrysin (20 mg/kg) once a day for 28 consecutive days. At the end of the treatments, behavioral tests were performed: open-field test (OFT) and morris water maze (MWM). Then, the levels of neurotrophins (BDNF and NGF) in the hippocampus and prefrontal cortex were measured and tested the affinity of chrysin with neurotrophinergic receptors through molecular docking. Hypothyroid mice showed memory deficit in the MWM and reduced neurotrophins levels in the hippocampus and prefrontal cortex, meanwhile, the chrysin treatment was able to reversed the deficit of spatial memory function and increased the levels of BDNF in hipocamppus and NGF in both structures. Additionally, molecular docking analysis showed that chrysin potentially binds to the active site of the TrkA, TrkB, and p75NTR receptors. Together, these findings suggest that chrysin reversed behavioral and neurochemical alterations associated with memory deficit induced by hypothyroidism, possibly by modulating synaptic plasticity in the neurotrophinergic system.