Thyroxine Concentrations Research Articles

Гипотиреоз у долгожителей: благо или вред?

Aim. To analyze the relationship of thyroid hormones with various clinical and laboratory parameters in centenarians with coronary artery disease (CAD) based on the determination of the blood concentration of thyroid-stimulating hormone (TSH), free triiodothyronine (T3) and free thyroxine (T4). Materials and methods. This work was a cross-sectional study conducted on the basis of the Hospital for War Veterans No. 3. The study enrolled 262 patients [195 (74.4%) women and 67 (25.6%) men] aged 90 to 101 years (mean age 92.9±2.5 years) hospitalized with a diagnosis of coronary artery disease. The concentration of thyroid-stimulating hormone (normal 0.27–4.2 μIU/ml), the level of free T4 (12–22 pmol/l) and free T3 (3.1–6.8 pmol/l) in the blood were determined. Results. The mean level of TSH was 3.1±3.1 μIU/ml (0.005–108), free T3 – 3.7±0.65 pmol/l (1.9–5.3), free T4 – 14.1±5.5 pmol/l (4.1–32). In 18.9% of patients, the level of TSH was elevated, in 3.9% it was reduced, in 77.2% of patients it was normal. In patients with increased TSH lower functional activity was noted, assessed using the Barthel index (66.9±23.0 compared to 75.0±16.4 points in patients with normal TSH; p=0.02) and the IADL scale (3.46±2.3 and 4.6±2.0 points, respectively; p=0.006). Direct correlations were registered between free T4 concentration and uric acid (r=0.28; p=0.05), cholesterol (r=0.35; p=0.01), triglycerides (r=0.37; p=0.08), hemoglobin (r=0.23; p=0.07) and Morse fall scale (r=0.34; p=0.05). Significant inverse correlations were established between the blood concentration of free T4 and absolute indicators of bone mineral density in the lumbar spine (r=-0.36; p=0.03), in the proximal left (r=-0.44; p=0.006) and right (r=-0.43; p=0.009) femur. Conclusion. The study results demonstrate the relationship between the concentration of thyroid hormones and various clinical and laboratory parameters in centenarians with coronary heart disease.

Heat tolerance in Mashona beef cows in semi-arid rangelands: does conformation matter?

High temperatures and frequent heat waves raise concerns about heat stress in cattle in grass-based systems, especially in arid and semiarid areas. This study analysed the relationship between conformation traits and physiological parameters associated with heat stress in Mashona cattle. A total of 200 records from fifty cows were used to study the relationships between seven conformation traits and physiological parameters associated with heat stress. Body conformation traits were categorised into three principal components related to body capacity (body depth, flank circumference, chest girth), frame size (stature and body length), and loose skin fold (navel height and dewlap size). As the size of abdominopelvic and thoracic cavities increased, respiratory rate, heart rate, and rectal temperature decreased significantly, while blood triiodothyronine concentration increased. Cattle with deeper bodies, larger flanks, and larger chest girths had significantly lower heart rate, respiratory rate, and rectal temperature but higher blood triiodothyronine concentration than cattle with shallower bodies, smaller flanks, and smaller chest girths. Respiratory rate increased with increasing frame size. Large-framed cattle had significantly higher respiratory rate and lower blood thyroxine concentration. Small-framed cattle with larger chest girth, larger dewlap, and navel farther from the ground surface are better adapted to higher ambient temperatures.

Effects of varying doses of conjugated estrogen on body weight, hormonal and histological alterations of reproductive organs in adult swiss albino female mice

Estrogens are a group of hormones that have diverse effects on both reproductive and non-reproductive organs. Conjugated estrogens are medicine that contains a mixture of estrogen hormones. The study was conducted to observe the effects of varying doses of conjugated estrogen on body weight, hormonal and histological alterations of reproductive organs in adult swiss albino female mice. In this study, 60 female swiss albino mice (Mus musculus) aged 28–30 days with an average body weight of 28.2 ± 1 g were used. At first, the mice were randomly divided into 4 groups each containing 15 mice. Group A was served as vehicle control and fed on standard mice pellet and fresh drinking water. While, groups B, C and D were administered with conjugated estrogen orally at the daily dose rate of 125 μg, 250 μg and 500 μg/kg body weight respectively with 1 mL sesame oil as a vehicle by mixing with feed. The experiment was carried out for 90 days. After humanly euthanized, blood was collected and serum was prepared and organs were collected for histopathology. The results revealed that higher doses of conjugated estrogen resulted in weight loss in premenopausal female mice compared to lower doses. Serum estrogen and thyroxine concentration was increased significantly following the doses of conjugated estrogen. Ovarian histotexture showed congested blood vessels and cystic space with degeneration of follicles and corpus luteum. Uterine lesions included massive macrophage infiltration in endometrium and hyperplasia of glandular epithelium at a lower dose; hyperplasia and hypertrophy of glandular epithelium (pleomorphism) with normal macrophage infiltration in endometrium at a higher dose. Therefore, it can be concluded that oral conjugated estrogen therapy at high dose has more detrimental impacts on body weight and reproductive function compared to lower dose in female adult mice.

Fast Track Treatment of Hypothyroidism with Levothyroxine: Reaching Homeostasis within Four Weeks

With the current clinical method for the treatment of hypothyroidism the target for the optimum individual values for free thyroxine concentrations [FT4] and thyrotropine concentrations [TSH] of the specific patient are unknown. This situation leads to unnecessary long experimental medication administration that can take a period of sometimes one year. In this article a method will be described where hypothyroid patients are characterized with weekly measured FT4 and TSH concentrations during the first three weeks of synthetic thyroxine or levothyroxine (L-T4) treatment to predict their optimum [FT4] and belonging [TSH] endpoint for a euthyroid homeostatic state. The treatment with levothyroxine will start for all patients with a reference dose of 100µg, which can be adjusted by the treating physician to a more safe and appropriate dose for the individual which is monitored with weekly thyroid function tests to observe the progress. After three weeks all characteristics of the patient can be inferred from the measured data. Thefinal titration target together with the individual thyroxine half life can be calculated. With the known characteristics and the L-T4 titration target the clinician or treating physician has an instrument to reduce the experimental treatment burden for the patient from one year to a maximum of four weeks.

Helicobacter pylori infection increase the risk of subclinical hyperthyroidism in middle-aged and elderly women independent of dietary factors: Results from the Tianjin chronic low-grade systemic inflammation and health cohort study in China.

Prospective studies on the association between Helicobacter pylori (H. pylori) infection and subclinical hyperthyroidism are limited. We, therefore, designed a large-scale cohort study to explore the association between H. pylori infection and the risk of subclinical hyperthyroidism in women. This prospective cohort study investigated 2,713 participants. H. pylori infection was diagnosed with the carbon 13 breath test. Subclinical hyperthyroidism was defined as serum thyroid-stimulating hormone levels are low or undetectable but free thyroxine and tri-iodothyronine concentrations are normal. Propensity score matching (PSM) analyses and Cox proportional hazards regression models were used to estimate the association between H. pylori infection and subclinical hyperthyroidism. A total of 1,025 PS-matched pairs of H. pylori infection women were generated after PSM. During 6 years of follow-up, the incidence rate of subclinical hyperthyroidism was 7.35/1,000 person-years. After adjusting potential confounding factors (including iodine intake in food and three main dietary patterns score), the multivariable hazard ratio (HR; 95% confidence intervals) of subclinical hyperthyroidism by H. pylori infection was 2.49 (1.36, 4.56). Stratified analyses suggested a potential effect modification by age, the multivariable HR (95% confidence intervals) was 2.85 (1.45, 5.61) in participants aged ≥ 40 years and 0.70 (0.08, 6.00) in participants aged < 40 years (P for interaction = 0.048). Our prospective study first indicates that H. pylori infection is significantly associated with the risk of subclinical hyperthyroidism independent of dietary factors among Chinese women, especially in middle-aged and older individuals.Clinical Trial Registration:https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000031137, identifier UMIN000027174.

Growth and Plasma Triiodothyronine Concentrations Are Modified by Selenium Deficiency and Repletion in Second-Generation Selenium-Deficient Rats

Classical glutathione peroxidase (GPX) is a useful Se-dependent parameter for determining Se status, but loss of GPX activity alone cannot explain the full effects of Se deficiency. The recent identification of type I thyroxine 5′-deiodinase as a Se-dependent enzyme provides a new potentially critical role for Se. To develop a model of impaired growth due to Se deficiency, second generation deficient weanling rats were fed a Se-deficient amino acid diet with adequate vitamin E and methionine. Initial growth rates of deficient males and females were 53 and 63%, respectively, of rats fed 0.1 µg Se/g diet. In short-term experiments with deficient males, liver Se and GPX activity were reduced 99%, liver glutathione-s-transferase activity was increased 114%, plasma thyroxine concentrations were increased 67%, plasma triiodothyronine was decreased 23% and the plasma triiodothyronine:thyroxine ratio was decreased 55%, compared with rats fed 0.2 µg Se/g diet. When deficient rats were injected on d 14 with 0, 1, 5 or 10 µg Se/100 g, rats grew 4.45, 7.62, 7.17 and 9.05 g/d, respectively, over the next 7 d. Injection with 10 µg Se/100 g restored plasma thyroxine and triiodothyronine concentrations 7 d later. Rats injected with 1 µg Se/100 g rat had significantly altered plasma thyroxine and triiodothyronine concentrations 1 but not 7 d after injection. Infusion of Se-deficient rats with 438 ng triiodothyronine/d for 7 d restored plasma triiodothyronine concentrations but did not increase growth rate compared with rats infused with saline. This model produced a significant growth depression that was significantly reversed by as little as 1 µg Se/100 g rat, but not by triiodothyronine infusion, suggesting that other Se-dependent roles in addition to 5′-deiodinase and GPX are necessary for adequate growth.

Selenium Deficiency Alters Thyroid Hormone Metabolism in Guinea Pigs

In guinea pigs, activity of glutathione peroxidase in most organs is markedly lower than in organs of other rodents despite comparable dietary intakes and tissue levels of selenium. To determine if metabolism of selenium with respect to other selenoproteins also differs in guinea pigs, we measured the effects of selenium intake on thyroid hormone metabolism. Weanling male Hartley Albino guinea pigs were fed a selenium-deficient Torula yeast-based diet, or the same diet supplemented with 0.5 mg selenium/kg diet as sodium selenate for 72 d. Growth was impaired in guinea pigs fed the unsupplemented diet. Activity of glutathione peroxidase was higher in tissues and plasma of supplemented guinea pigs than in selenium-deficient animals. However, it was still far lower than reported values for other rodent species. In selenium deficiency, activity of type 1 5′-iodothyronine deiodinase was 60% less in liver and 45% less in kidney. Concentration of thyroxine was 68% lower in kidney of selenium-deficient animals, and levels of 3,3′,5-triiodothyronine in kidney and plasma were 44 and 31% lower, respectively. Thus, with the exception of thyroxine concentrations, thyroid hormone metabolism responds to selenium deficiency in guinea pigs as it does in rats, although the magnitude of that response is not as great.

Machine learning to improve false-positive results in the Dutch newborn screening for congenital hypothyroidism

ObjectiveThe Dutch Congenital hypothyroidism (CH) Newborn Screening (NBS) algorithm for thyroidal and central congenital hypothyroidism (CH-T and CH-C, respectively) is primarily based on determination of thyroxine (T4) concentrations in dried blood spots, followed by thyroid-stimulating hormone (TSH) and thyroxine-binding globulin (TBG) measurements enabling detection of both CH-T and CH-C, with a positive predictive value (PPV) of 21%. A calculated T4/TBG ratio serves as an indirect measure for free T4. The aim of this study is to investigate whether machine learning techniques can help to improve the PPV of the algorithm without missing the positive cases that should have been detected with the current algorithm. Design & methodsNBS data and parameters of CH patients and false-positive referrals in the period 2007–2017 and of a healthy reference population were included in the study. A random forest model was trained and tested using a stratified split and improved using synthetic minority oversampling technique (SMOTE). NBS data of 4668 newborns were included, containing 458 CH-T and 82 CH-C patients, 2332 false-positive referrals and 1670 healthy newborns. ResultsVariables determining identification of CH were (in order of importance) TSH, T4/TBG ratio, gestational age, TBG, T4 and age at NBS sampling. In a Receiver-Operating Characteristic (ROC) analysis on the test set, current sensitivity could be maintained, while increasing the PPV to 26%. ConclusionsMachine learning techniques have the potential to improve the PPV of the Dutch CH NBS. However, improved detection of currently missed cases is only possible with new, better predictors of especially CH-C and a better registration and inclusion of these cases in future models.

Hypothyroidism impairs development of the gastrointestinal tract in the ovine fetus.

Growth and maturation of the fetal gastrointestinal tract near term prepares the offspring for the onset of enteral nutrition at birth. Structural and functional changes are regulated by the prepartum rise in cortisol in the fetal circulation, although the role of the coincident rise in plasma tri-iodothyronine (T3) is unknown. This study examined the effect of hypothyroidism on the structural development of the gastrointestinal tract and the activity of brush-border digestive enzymes in the ovine fetus near term. In intact fetuses studied between 100 and 144days of gestation (dGA; term ∼145days), plasma concentrations of T3, cortisol and gastrin; the mucosal thickness in the abomasum, duodenum, jejunum and ileum; and intestinal villus height and crypt depth increased with gestational age. Removal of the fetal thyroid gland at 105-110 dGA suppressed plasma thyroxine (T4) and T3 concentrations to the limit of assay detection in fetuses studied at 130 and 144 dGA, and decreased plasma cortisol and gastrin near term, compared to age-matched intact fetuses. Hypothyroidism was associated with reductions in the relative weights of the stomach compartments and small intestines, the outer perimeter of the intestines, the thickness of the gastric and intestinal mucosa, villus height and width, and crypt depth. The thickness of the mucosal epithelial cell layer and muscularis propria in the small intestines were not affected by gestational age or treatment. Activities of the brush border enzymes varied with gestational age in a manner that depended on the enzyme and region of the small intestines studied. In the ileum, maltase and dipeptidyl peptidase IV (DPPIV) activities were lower, and aminopeptidase N (ApN) were higher, in the hypothyroid compared to intact fetuses near term. These findings highlight the importance of thyroid hormones in the structural and functional development of the gastrointestinal tract near term, and indicate how hypothyroidism in utero may impair the transition to enteral nutrition and increase the risk of gastrointestinal disorders in the neonate.

Short-term physiological responses to moderate heat stress in grazing dairy cows in temperate climate.

Even in temperate climate regions, an increase in ambient temperature and exposure to solar radiation can cause heat stress in lactating dairy cows. We hypothesised that grazing dairy cows exhibit short-term physiological changes due to increasing heat load under moderate climate conditions. Over two consecutive summers, 38 lactating Holstein dairy cows were studied in a full-time grazing system. Data were collected in 10 experimental periods of up to three consecutive days with a moderate comprehensive climate index (CCI). The individual animals' vaginal temperature (VT), heart rate, and locomotor activity data were automatically monitored with sensors. Blood samples and proportional whole milk samples were collected at afternoon milking. The concentrations of beta-hydroxybutyrate, glucose, non-esterified fatty acids, urea nitrogen, plasma thyroxine and triiodothyronine were analysed in blood plasma, and fat, protein, lactose, urea nitrogen, cortisol, Na+, K+, and Cl- concentrations were analysed in milk. The daily distribution of VT recordings greater than 39°C showed a circadian rhythm with a proportion of recordings of 2% and lower during the night and a percentage of 10% or higher in the afternoon. The cows' maximal daily vaginal temperature (VTMAX) between 0830 and 1430h was positively related to the mean daily CCI in the same time period (CCIMEAN; mean and SD 23.6±5.4°C). Cows with greater VTMAX had an increased mean heart rate, plasma glucose and milk cortisol concentrations and decreased concentrations of plasma thyroxine and triiodothyronine. The concentration of Na+ in milk was lower, and the concentration of K+ in milk tended to be higher in cows with increased VTMAX. For beta-hydroxybutyrate, non-esterified fatty acids and urea nitrogen concentrations in plasma and fat and lactose concentrations in milk no relationships were found in terms of increasing VT. For milk urea nitrogen and protein concentrations, the proportion of total variance explained by inter-individual or -period variance was high. In conclusion, changes observed in milk and blood likely reflected short-term physiological responses to moderate heat stress. In particular, milk cortisol and Na+ may be useful traits for timely monitoring of heat stress in individual cows because their inter-individual variances were relatively small and samples can be collected non-invasively.

Relationship between Dehydroepiandrosterone-Sulfate, Testosterone, Thyroid Hormones, Insulin and Cortisol in Indigenous Men and Women among Representatives of the Indigenous and Newcomer Population of the Yamalo-Nenets Autonomous Okrug

Using Spearman’s rank correlation we studied the correlations between the serum dehydroepiandrosterone-sulfate (DHEA-S) concenttration and the concentration of testosterone, thyroid-stimulating hormone, thyroxine, triiodothyronine, insulin and cortisol in the indigenous and alien populationof the Yamal-Nenets Autonomous Okrug. A positive correlation was found between the DHEA-S concenttration and testosterone in indigenous women and newcomers. A stronger correlation was found in the group of newcomer women. In indigenous men, DHEA-S was positively correlated with cortisol. The newcomer men showed a positive correlation between DHEA-S and thyroid-stimulating hormone. No correlations were found between the concenttration of DHEA-S with insulin, thyroxine and triiodothyronine in any of the examined groups.

Lower thyroid stimulating hormone concentrations linked to suicidal ideations among individuals with anxiety and mood disorders

IntroductionSuicidal behavior is quite common in individuals with anxiety and mood disorders (AMD). One of the coexistence factors in suicidal behavior is thyroid dysfunction, however the results are still controversial (Shen et al. J Affect Disord 2019;(1)180-185; Zhou et al., Transl Psychiatry. 2021;11(1):97). The role of thyroid function in suicidal ideation among individuals with comorbid AMD have not been thoroughly investigated.ObjectivesThe aim of this cross-sectional study was to identify potential associations between thyroid function and suicidal ideation in a sample of individuals with anxiety and mood disorders.MethodsThis exploratory study comprised 77 consecutive individuals with AMD (age range 18-73 years, 76% were females) attending the Psychiatry Day care unit. All individuals have been evaluated for current psychiatric diagnoses, suicidal ideation using the Mini International Neuropsychiatric Interview [M.I.N.I. 7.0.2]) as well as for socio-demographic factors and for current psychotropic medication use. Severity of depression and anxiety symptoms have been evaluated using the Patient Health Questionnaire-9 (PHQ-9) and the General Anxiety Disorder-7 (GAD-7). The biochemical blood tests were performed for the concentrations of thyroxine (FT4), triiodothyronine (FT3) and thyroid stimulating hormone (TSH). The univariate and multivariable logistic regression analyses were used to assess the association between biochemical parameters and suicidal ideation.ResultsOf all study individuals with AMD – 56% have been identified as having current SI. There were not significant differences according to age, gender, education, BMI, smoking, depression and anxiety symptoms and current psychotropics use between SI and non-SI individuals. Serum FT4, FT3 and TSH concentrations were within normal range. However individuals with SI had significantly lower TSH concentrations in comparison to the non-SI (1.54 (0.77) vs. 2.04 (1.22) IU/L, respectively; p = 0.049), without significantly differences in FT4 and FT3 concentrations. A multiple logistic regression, adjusting for sociodemographic factors and severity of mental symptoms revealed, that non-SI individuals with AMD were likely to have higher TSH levels than SI (odds ratio = 2.15 (95% CI 1.10–4.22; p = 0.027).ConclusionsAmong individuals with AMD, lower levels of TSH concentrations have been associated with presence of suicidal ideation, independently of sociodemographic factors and severity of depression and anxiety.Disclosure of InterestV. Liaugaudaitė Grant / Research support from: European Union (project No P-PD-22-150) under the agreement with the Research Council of Lithuania (LMTLT)., A. Podlipskytė: None Declared, J. Burkauskas Consultant of: Cronos, N. Mickuvienė: None Declared, V. Adomaitienė: None Declared, E. Zauka: None Declared, V. Steiblienė: None Declared

Thyroidectomy in dogs with thyroid tumors: Survival analysis in 144 cases (1994-2018).

Few studies have assessed predictors of outcome in dogs with thyroid tumors undergoing thyroidectomy. To estimate the survival and identify prognostic factors in dogs with thyroid tumors treated by thyroidectomy. A total of 144 client-owned dogs with thyroid neoplasia that underwent thyroidectomy. Retrospective study. Data for analysis included hospital attended and year of surgery, signalment, thyroxine concentration, thyroid tumor features (lobe involvement, size, invasiveness, histopathological type), thrombosis, metastasis, additional surgery and therapy, administration of adjuvant chemotherapy. The association of predictors with survival (time from surgery to death) were assessed by calculating cause-specific hazard ratios (HRcs ) and 95% confidence intervals (CI). Causes of death were classified as thyroid-related or because of other cause. Overall median survival time was 802 days (CI95%=723-1015 days); 89 dogs (77.4%) survived >500 days. Metastases were identified at admission in 12 (8.3%) dogs and were associated with higher thyroid cancer-related fatality (HR=5.83, CI95%=1.56-21.78; P= .009). Thrombosis occurred in 40 dogs and was associated with increased risk of death because of other cause (HR=2.73, CI95%=1.18-6.35; P= .019). Nonfollicular carcinoma (HR=4.17, CI95%=1.27-13.69; P= .018) and administration of chemotherapy (HR=3.45, CI95%=1.35-8.82; P= .01) were associated with higher risk of thyroid cancer-relateddeath. Dogs with thyroid tumors undergoing thyroidectomy have a long life expectancy. Despite the rare presence of nonfollicular carcinoma and metastases, thyroidectomy should still be considered in some of these dogs.

Rat Serum Osteocalcin Concentration Is Decreased by Restriction of Energy Intake

We studied the effects of energy restriction on serum osteocalcin concentration and bone formation rate in rats. The experiment was designed to achieve energy restriction by reducing the carbohydrate intake while providing identical quantities of protein, fat, vitamins and minerals. Energy intakes of three groups of post-weaning male rats were restricted by 20, 40 and 60% for 4 wk. Serum calclum, phosphorus, transthyretin, triiodothyronine (T3), thyroxine (T4), 1,25-dihydroxycholecalciferol, 25-hydroxycholecalciferol and immunoreactive parathyroid hormone (iPTH) concentrations were determined. Energy restriction (20, 40 and 60%) produced a significant and gradual drop of serum osteocalcin concentrations, although the serum concentrations of its key regulators, i.e., 1,25-dihydroxycholecalciferol and iPTH, were not significantly affected. On the contrary, serum concentrations of calcium, phosphorus, transthyretin, T3 and T4 were significantly lower in the energy-restricted groups. However, our results do not support their implication in the regulation of serum osteocalcin synthesis by energy intake. Serum osteocalcin concentration was positively correlated with bone mineral apposition (r = 0.50, P < 0.05) and bone mineralization (r = 0.50, P < 0.05) rates suggesting that its decrease resulted from a reduction of bone formation, and not from abnormal mineralization, because osteoid seam thickness was not modified. Energy intake seems to be an important determinant of serum osteocalcin concentration and bone formation; however, the exact mechanism underlying this regulation remains to be determined.

Soy Protein Concentrate and Isolated Soy Protein Similarly Lower Blood Serum Cholesterol but Differently Affect Thyroid Hormones in Hamsters

There is a wide variation in the hypocholesterolemic response to ingestion of soy protein in humans. One possible explanation is that the different soy protein preparations used contain different spectra of biologically active components. This could affect a number of indices including thyroid hormone status. An increased level of thyroxine has been proposed as an underlying mechanism of the hypocholesterolemic effect of soy protein. The objective of this study was to determine if serum cholesterol and thyroid hormone concentrations differed because of feeding soy protein from different sources. Twenty-nine male weanling golden Syrian hamsters were fed rations containing 25 g/100 g protein from either isolated soy protein (ISP), soy protein concentrate (SPC) or casein for 35 d. Serum total cholesterol concentrations were lower in hamsters fed ISP and SPC compared with those fed casein (P < 0.05). No differences in cholesterol concentrations were observed in lipoprotein fractions. Serum thyroxine and free thyroxine were greater only in hamsters fed ISP than in those fed casein (P < 0.05), whereas triiodothyronine concentrations were higher in casein-fed than in SPC-fed hamsters (P < 0.05). Results indicate that protein from ISP and SPC are both effective in lowering blood cholesterol concentrations, whereas only ISP increases thyroxine concentrations. Therefore, it appears unlikely that modulation of thyroid hormone status is responsible for the cholesterol-lowering effect of soy protein.

Increased fT4 concentrations in patients using levothyroxine without complete suppression of TSH.

In our hospital, physicians noticed high free thyroxine (fT4) concentrations without complete suppression of thyroid-stimulating hormone (TSH) in blood samples of patients at the outpatient clinic, which appeared to occur more often following the introduction of a new fT4 immunoassay. This discordance may be explained by incorrect reference intervals, analytical issues, or patient-related factors. We aimed to establish the contribution of the possible factors involved. Reference intervals of both fT4 immunoassays were re-evaluated using blood samples of healthy volunteers and the new immunoassay's performance was assessed using internal quality controls and external quality rounds. The frequency of discordant fT4 and TSH pairings obtained from laboratory requests were retrospectively analysed using a Delfia (n = 3174) and Cobas cohort (n = 3408). Last, a literature search assessed whether the time of blood draw and the time of levothyroxine (L-T4) ingestion may contribute to higher fT4 concentrations in L-T4 users. The original reference intervals of both fT4 immunoassays were confirmed and no evidence for analytical problems was found. The Delfia (n = 176, 5.5%) and Cobas cohorts (n = 295, 8.7%) showed comparable frequencies of discordance. Interestingly, 72-81% of the discordant results belonged to L-T4 users. Literature indicated the time of blood withdrawal of L-T4 users and, therefore, the time of L-T4 intake as possible explanations. High fT4 without suppressed TSH concentrations can mainly be explained by L-T4 intake. Physicians and laboratory specialists should be aware of this phenomenon to avoid questioning the assay's performance or unnecessarily adapting the L-T4 dose in patients.

Subclinical Hypothyroidism is Associated with Cognitive Impairment in Patients with Cerebral Small Vessel Disease.

To investigate the association between subclinical hypothyroidism (SCH) and cognitive function in patients with cerebral small vessel disease (CSVD). We evaluated 528 patients with CSVD in this retrospective study. SCH was defined as elevated levels of thyroid stimulating hormone with normal concentrations of free thyroxine. Magnetic resonance imaging was performed to assess the total CSVD burden score and the Montreal Cognitive Assessment was used to measure the cognitive function. Participants were grouped based on cognitive function or total CSVD burden score. Multivariate logistic regression and mediation analysis models were used to estimate the association of SCH with cognitive function and CSVD burden. SCH was an independent risk factor for cognitive impairment in patients with CSVD after adjustment for potential confounding factors (OR: 1.939; 95% CI: 1.170 to 3.213; P=0.010). Additionally, SCH was independently associated with severe CSVD burden after adjustment for potential confounding factors (OR: 1.668; 95% CI: 1.085 to 2.564; P=0.020). Mediation analysis found a significant moderating effect (P=0.021) of the severe CSVD burden on the relation between SCH and cognitive impairment after adjustment for potential confounding factors. A 30.1% of the total effect between this relation was attributable to the presence of severe CSVD burden. SCH was associated with an increased risk of cognitive impairment in patients with CSVD. The mediating role of severe CSVD burden suggests that SCH may lead to cognitive impairment through the presence of severe CSVD burden. These findings may suggest strategies for screening for SCH in the context of cognitive impairment in patients with severe CSVD.

Thyroid hormone dynamics of Tharparkar and Sahiwal cattle during induced heat stress

Thyroid hormones and Cortisol level are the essential biomarkers in the assessment of stress condition. This study was done to estimate the metabolic hormonal profile of Tharparkar and Sahiwal during heat stress condition. The experiment was conducted on two groups consisting of Tharparkar and Sahiwal animals (5 in each group) and the experimental period comprised a 7-day acclimatization period, a heat exposure period of 21days at control (25°C), moderate (35°C) and severe (42°C) heat stress within a 9-10-day recovery period between each exposure. The hormonal concentrations of T3, T4 and cortisol were determined in serum. The serum concentration of Thyroxine (T4) and tri-iodothyronine (T3) decreases whereas cortisol level increases in both the breeds when subjected to heat stress. However, the serum level of T4 was significantly (p < 0.05) more declined in Sahiwal as compared to Tharparkar but there was no significant difference found between the two breeds in serum T3 levels. The cortisol levels were elevated in both breeds during heat stress but significantly (p < 0.05) more elevated in the Sahiwal. Hence, observations of these hormonal profiles suggest a better thermo-adaptability in Tharparkar as compared to Sahiwal.

Effect of body condition score on biochemical parameters and hormonal profiles during the mating period in Ouled Djellal ewes in arid zone

ABSTRACTThis study aims to evaluate the effect of body condition score (BCS) on hormonal profiles and to reveal their influence on the blood metabolites in Ouled Djellal ewes during the mating period. The experiment was conducted on thirty, clinically healthy and non-pregnant, Ouled Djellal ewes which have been kept into two groups according to their body condition score (Group I: BCS &lt; 2.50 units; n = 13, Group II: BCS &gt; 2.50 units; n = 17). In both groups, oestrus was synchronized using hormonal patterns then the ewes were left to be naturally inseminated. Blood samples were collected at the time of the sponge removal. Plasma concentrations of glucose, triglycerides, cholesterol, total protein, albumin, creatinine, urea, triiodothyronine, thyroxine and Progesterone were recorded. The plasma level of triglycerides and thyroid hormones (T3 and T4) increase significantly (P &lt; 0.01) in group II. Progesterone concentrations were similar (P ≥ 0.05) in both groups at mating period, although we recorded higher rate in group I. Therefore, we conclude that body condition score has a significant impact on some hormone profiles and blood parameters during the mating period.

Effect of Thyroxine on the Structural and Dynamic Features of Cardiac Mitochondria and Mitophagy in Rats.

This work investigated the effect of thyroxine on the biogenesis and quality control system in rat heart mitochondria. In hyperthyroid rats, the concentrations of free triiodothyronine and thyroxine increased severalfold, indicating the development of hyperthyroidism in these animals. The electron microscopy showed 58% of cardiac mitochondria to be in a swollen state. Some organelles were damaged and had a reduced number of cristae. Multilamellar bodies formed from cristae/membranes were found in the vacuolated part of the mitochondria. The hyperthyroidism caused no changes to mitochondrial biogenesis in the investigated animals. At the same time, the levels of mitochondrial dynamics proteins OPA1 and Drp1 increased in the hyperthyroid rats. The administration of thyroxine to the animals led to a decrease in the amount of PINK1 and Parkin in heart tissue. The data suggest that excess thyroid hormones lead to changes in mitochondrial dynamics and impair Parkin-dependent mitophagy in hyperthyroid rat heart.