Plasma Total T4 Research Articles

Iodine Bioavailability and Accumulation of Arsenic and Cadmium in Rats Fed Sugar Kelp (Saccharina latissima).

Suboptimal iodine status is a prominent public health issue in several European coun-tries. Brown algae have a high iodine content that, upon intake, may exceed the recommended dietary intake level, but iodine bioavailability has been reported to be lower than from potassium iodide (KI) and highly depends on algae species. Further, potential negative effects from other components in algae, such as cadmium (Cd) and arsenic (As), have also been addressed. In this study, we observed a lower bioavailability of iodine from farmed sugar kelp (Saccharina latissima) than from KI in female Wistar IGS rats. Urinary iodine excretion was 94-95% in rats fed KI and 73-81% in rats fed sugar kelp, followed by increased faecal iodine levels in rats fed sugar kelp. No effects on body weight, feed efficiency, or plasma markers for liver or kidney damage were detected. The highest dose of iodine reduced plasma free thyroxine (fT4) and total T4 levels, but no significant effects on circulating levels of thyroid-stimulating hormone (TSH) and free triiodo-thyronine (fT3) were detected. Faeces and urine measurements indicate that 60-80% of total As and 93% of Cd ingested were excreted in rats fed 0.5 and 5% kelp. Liver metabolomic profiling demonstrates that a high inclusion of sugar kelp in the diet for 13 weeks of feeding modulates metabolites with potential antioxidant activity and phytosterols.

Predictors of Serum TSH in a Healthy Adult Sample of the Lebanese Population

Purpose: Measuring thyroid-stimulating hormone (TSH) is essential for diagnosing and monitoring thyroid diseases. The aim of this study is to determine the factors predicting TSH variability. Materials and Methods: Plasma TSH, free T3 (FT3), total T3 (TT3), free T4 (FT4), anti-peroxidase antibodies (TPOAb) and anti-thyroglobulin antibodies (TgAb) were measured in 301 healthy Lebanese adults (198 women and 103 men) aged 18 to 65 years. Measurements were performed on the Cobas Roche automate. Age, sex, Body Mass Index (BMI), arterial blood pressure and the presence of dyslipidemia were collected from the population. Results: The mean age of the population was 38.98 ± 13.28 years and the mean BMI 25.36 ± kg/m². There was no correlation between TSH and FT4, while a positive correlation was found between TSH and TT3, FT3, TPOAb and TgAb (respectively p <0.001, p=0.002, p<0.0001and p< 0.0001). TSH was not associated with age or gender but was positively correlated with BMI (p=0.053) and systolic blood pressure (p=0.03).In a multiple linear regression analysis, the independent predictors of TSH were FT4, FT3 and TPOAb. In addition, FT4, TPOAb, and dyslipidemia were independently associated with the TSH 97.5th percentile. Conclusion: Our study showed that the main predictors of TSH are FT4, FT3 and TPOAb. This finding supports the role of TSH in enhancing T3 production as well as the main role of TPOAb in predicting the rise in TSH.

EFFECT OF USING MORINGA OLEIFERA LEAVES ON PRODUCTIVE PERFORMANCE AND SOME PHYSIOLOGICAL PARAMETERS OF JAPANESE QUAIL

A total number of eighty four unsexed 7 day old Japanese quail chicks were randomly divided into among four 4 dietary treatments with 3 replicate (7 birds), assigning experimental unit to investigate the effect of feeding Japanese quail chicks on diets containing different levels of Moringa oleifera leaves (MOL) on productive performance, blood constituents, hormones, antioxidant indices, immunity parameters and carcass characteristics. Dietary treatments were: The first group (control) fed a basal diet, while the other three groups were fed a basal diet supplemented with 3, 5 and 7 g of MOL / kg diet during the experimental period until 6 weeks age. Results showed that treated groups had significantly greater body weight, body weight gain, feed intake, improved feed conversion and increased significantly percentage of dressing and internal organs as well as higher values of nutrients digestibility than the control group. All treatments increased significantly (P<0.05) some blood constituents: RBCs, Hb and PCV, WBCs, plasma total protein, albumin, Ca, HDL, GPX,GSH, SOD, TAC, IgG, and T4 hormones, while plasma cholesterol, total lipids, LDL, AST, ALT and glucose were decreased. There was no effect on phosphorus (P) compared to control. It could be concluded that adding Moringa oleifera leaves at levels of 3, 5 and 7 g of MOL/kg diet improved productive performance, nutrients digestibility, blood constituents, hormones, antioxidant indices, immunity parameters and carcass characteristics

Validation of plasma thyroxine and triiodothyronine methods on the ADVIA Centaur® XP

Standardization programs for thyroid hormones have revealed bias between immunochemical methods and the reference method ED-ID-LC/MS. Lack of standardization between methods, suboptimal reference intervals and replacement of serum with plasma may compromise the capability of the immunochemical thyroid methods to diagnose thyroid disease. To accommodate the demand for faster turn-around times for laboratory replies, we replaced serum with plasma on some serum CE marked thyroid methods. This forced us to do on-board analytical correction for the plasma total T4 (TT4) method on ADVIA Centaur® XP. We, next, validated the capability of the ADVIA Centaur® XP thyroid methods on plasma by (1) first carrying out a prospective method comparison with the ED-ID-LC/MS reference method using collected plasma samples, (2) we verified the clinical reference intervals by analyzing collected plasma samples from healthy individuals, and (3) retrospectively compared laboratory results from two different time periods using serum TT4 and serum total triiodothyronine (TT3) versus plasma free thyroxine (FT4) and plasma TT3, respectively, to diagnose thyroid disease. The plasma FT4 method displayed a negative concentration-dependent bias against the reference method. This bias was apparently counteracted by a fitted reference interval for the plasma FT4 method. Indeed, overt hyperthyroid disease was found in 1.0% and 1.1% of the cases using serum and plasma and overt hypothyroid condition were in 1.3% and 0.6% of the cases using serum and plasma, respectively. In conclusion, the ADVIA Centaur® XP FT4 method displayed a negative bias at high plasma FT4 concentrations against the reference method, but the diagnostic performance was not compromised due to a fitted reference interval.

Changes in thyroid axis responses in two ring-billed gull sub-populations differentially exposed to halogenated flame retardants

Developing bird embryos may be affected by a number of thyroid disrupting chemicals through maternal transfer. However, thyroid disruption in developing embryos of wild birds remains largely unstudied, especially with respect to exposure to ubiquitous environmental contaminant classes including halogenated flame retardants (HFRs). The objective of the present study was to investigate responses of the hypothalamic-pituitary-thyroid (HPT) axis of developing birds that are exposed to elevated concentrations of HFRs in their environment. Ring-billed gulls (Larus delawarensis) were collected at the external pipping stage (i.e., just prior to hatching) from two sub-populations that are differentially exposed to HFRs in the St. Lawrence River (QC, Canada). Plasma levels of thyroid hormones (THs) and transcription levels of thyroid-related genes in three tissues (i.e., liver, thyroid gland and brain) were related to liver concentrations of HFRs in pipping gulls from these two colonies. Liver polybrominated diphenyl ether (PBDE) concentrations were negatively correlated with plasma total T4 and total T4/T3 in pipping ring-billed gulls. Moreover, plasma TH levels and hepatic PBDE concentrations were correlated with the transcription of genes involved in metabolism (deiodinases type 1, 2 and 3) and synthesis (sodium iodide symporter and thyroglobulin) in the thyroid gland, negative feedback loop (thyrotropin and corticotropin releasing hormones) in the brain and the pituitary and targeted action (TH receptors) in the three tissues of gulls. The present study suggested that the alteration of TH homeostasis in developing wild birds through changes in the transcription of several thyroid-related genes may be related to potential PBDE-mediated effects.

EFFECT OF FASTING REGIMEN AND DIETARY ZINC SUPPLEMENTATION ON HEMATOLOGICAL PARAMETERS, HORMONAL PROFILES AND ANTIOXIDANT PROPERTIES IN MALES OF GROWING RABBITS

The objective of the present study was to evaluate the effect of fasting regimen and dietary zinc (Zn) supplementation on hematological parameters, blood biochemical components, hormonal profiles and the antioxidative properties in males of growing rabbits. A total of 60 weaned male V-Line rabbits (35 days old) were randomly divided into six experimental treatments (10 each): (1) control (basal diet ad labium without any supplementation of Zn); (2) Ad+Zn (basal diet ad labium +100 mg Zn/kg diet); (3) F24 (24 hr fasting regimen per week); (4) F48 (48 hr fasting regimen per week); (5) F24+Zn (24 hr fasting regimen per week+100 mg Zn/kg diet) and (6) F48+Zn (48 hr fasting regimen per week+100 mg Zn/kg diet). All experimental treatments were provided from 35 to 84 day of age. The obtained results showed that fasting regimen (in experimental groups F24 and F48) decreased significantly red blood cells (RBCs) compared with those of control (Ad) or Ad+Zn groups in growing rabbits (P≤ 0.0001). While, group F48 recorded the lowest value of blood hemoglobin concentration (Hb) and packed cell volume (PCV). Dietary Zn supplementation relieved the effect of fasting in groups F24+Zn and F48+Zn. Regarding to white blood cells (WBCs) count, the lowest WBCs number was observed in F48 group compared with other treatments. The highest neutrophils percentages were recorded in groups supplemented with Zn (in groups Ad+Zn, F24+Zn and F48+Zn) compared with the other groups. No significant differences were observed in lymphocytes (%) monocytes (%) eosinophils (%) and basophils (%) among the experimental groups. Feeding growing rabbit's ad libitum diet supplemented with Zn (Ad+Zn) increased significantly blood plasma total protein and albumin concentration comparing with the other experimental groups. However, fasting regimen groups with or without Zn supplementation decreased significantly plasma total protein, albumin, glucose, total lipids, cholesterol and numerically triglycerides concentrations comparing with those fed ad libitum diet with or without Zn supplementation. Growing rabbits exposed to fasting (F24, F48, F24+Zn and F48+Zn groups) had a significant increase in blood plasma aspartate aminotransferase (AST), while, growing rabbits exposed to fasting with Zn (F24 and F48 groups) had a significant increase in blood plasma alanine aminotransferase (ALT) compared with those fed ad libitum diet with or without Zn supplementation (Ad and Ad+Zn groups). Total antioxidant capacity (TAC) was significantly increased in the group fed ad libitum diet supplemented with Zn (Ad+Zn) compared with the other experimental groups. However, TAC was significantly reduced in growing rabbit subjected to fasting regimen (24 or 48 h) and dietary Zn supplementation alleviated this effect and improved TAC significantly. Growing rabbits exposed to fasting (F24, F48, F24+Zn and F48+Zn groups) had a significant increase in plasma malonylaldhyed (MDA) concentration, cortisol, corticosterone and significantly decrease in blood plasma triiodothyronine (T3), thyroxin (T4) compared with those fed ad libitum diet (Ad) and ad libitum diet + Zn (Ad+Zn). It could be concluded that growing rabbits exposed to fasting and fed diet supplemented with or without Zn had a significantly decrease in RBCs, Hb concentration, PCV, plasma total protein, albumin, glucose, total lipids, cholesterol, triglycerides, T3 and T4 concentrations. Interestingly, dietary Zn supplementation improved the antioxidative properties and reduced the rate of lipid peroxidation in growing rabbits subjected to fasting regimen.

Is Dopamine an Iatrogenic Disruptor of Thyroid and Cortisol Function in the Extremely Premature Infant?

Background. Dopamine is frequently used as an inotropic and vasoactive agent in neonatal intensive care units. Recent studies have reported that treatment with dopamine is associated with hypothyroxinaemia of prematurity. Objectives. The aim of this study was to determine if dopamine treatment in extremely premature infants altered thyroid and cortisol function. Methods. We prospectively measured plasma cortisol, TSH, free T4, total T4, and free triiodothyronine concentrations in babies born below 28 weeks’ gestation within 5 days of birth, who were either treated with dopamine (D+) or who did not receive any dopamine (D−) within 12 hours of birth. Clinical Risk Index for Babies scores, lowest mean arterial pressure and highest plasma lactate concentrations in the first 12 hours, were recorded. Results. There were 78 babies included in the study (43 males). Mean gestational age was 25 weeks and 3 days (SD 1.3 weeks). Univariate analyses showed significant differences in cortisol and thyroid function between D+ and D−. Multivariable analyses showed that dopamine, gestation, and CRIB were independent factors affecting FT4 concentrations. No independent factors were shown to affect cortisol or TSH concentrations. Conclusion. Dopamine administration appeared to affect FT4 concentrations but not cortisol concentrations. The mechanisms are unclear but the effect does not appear to be related to hypotension or tissue underperfusion.

Inhibition of angiotensin II increases hypothalamic thyroid hormone and stimulates orexigenic NPY/AgRP neurons (LB437)

We have demonstrated that mice lacking renin (Ren1c ‐/‐) are lean and resistant to diet‐induced obesity, which is associated with increased energy expenditure and uncoupling proteins (UCPs) expression. Surprisingly, plasma catecholamine levels of Ren1c‐/‐ mice were similar to wild type (WT) mice, and their plasma total T3 and T4 were lower than those of WT, although they showed no obvious signs of hypothyroidism. We here investigate whether mice lacking renin display true hypothyroidism, and if so, the specific mechanism by which they develop it. The Ren1c‐/‐ mice have approximately 50% levels of free T3, freeT4 and TSH in the plasma, as well as reduced TRH expression in the hypothalamus compared to WT. Administration of TRH or angiotensin II (Ang II) both restored plasma TSH and thyroid hormones in the Ren1c‐/‐ mice, while these hormones were not affected by human renin, which stimulates mouse MAP kinases but does not cleave mouse angiotensinogen to Ang I. Moreover, the Ang II receptor blocker losartan decreased TRH, TSH, and thyroid hormones of WT mice to the levels similar to those in mice lacking renin. Furthermore, mice lacking renin and WT mice treated with losartan have significantly increased hypothalamic expression of type 2 deiodinase (Dio2), which converts T4 to the more potent T3, and have increased thyroid hormones in the hypothalamus, which likely inhibits TRH through feedback. Both mice lacking renin and WT mice treated with losartan have 3‐fold higher uncoupling protein‐2 (UCP2), orexigenic neuropeptide Y (NPY) and agouti‐related protein (AgRP), as well as 5‐fold lower anorexigenic proopiomelanocortin (POMC) gene expression in the hypothalamus relative to untreated WT mice. In contrast, Ren1c‐/‐ mice treated with human renin had similar expression levels of these genes. These results suggest that the inhibition of Ang II not of Ang‐independent effects of renin causes hypothyroidism and enhances food intake, which likely decrease energy expenditure. We hypothesize that changes in gene expression of the hypothalamus do not contribute to increased energy expenditure of the Ren1c‐/‐ mice, and that hypothalamic hyperthyroidism feedback inhibits TRH, leading to systemic hypothyroidism. Caution should be paid to hypothyroidism when using high dose of inhibitors of the renin angiotensin system.Grant Funding Source: National Science Council: 102‐2320‐B‐009 ‐002 ‐MY3

Thyroid hormone changes associated with prolonged food deprivation in adult male northern elephant seals (1101.6)

During food deprivation in mammals, thyroid hormone (TH) concentrations and deiodinase (DI) content is typically reduced to suppress metabolism. However, in metabolically active elephant seal pups the hypothalamic‐pituitary‐thyroid axis is up‐regulated during prolonged fasting. To better understand the mechanisms regulating the cellular function of TH in a fasting, yet metabolically active mammal, we measured plasma TH concentrations and mRNA expressions of DI type II (DI2) and TH receptor beta‐1 (THrβ‐1) in adult male northern elephant seals (n=8) over 8 weeks of fasting (early vs. late). We hypothesized that natural fasting in male seals decreases TH levels and DI expression. Fasting did not alter the concentrations of plasma reverse T3 and total T4. However, free T4 (0.25 ± 0.03 to 0.78 ± 0.08 ng/dL) and free T3 (0.61 ± 0.06 to 0.83 ± 0.08 pg/mL) increased between early to late fasting suggesting that there is an increased potential for TH‐mediated cellular effects. Conversely, total T3 decreased (63 ± 5 to 50 ± 4 ng/mL) suggesting that DI2 or DI3 may be contributing to the changes in TH metabolism. mRNA expressions of DI2 and THrβ‐1 decreased 87% ± 7 and 93% ± 2, respectively, between early to late fasting suggesting that there is a down‐regulation in cellular TH potential during fasting duration consistent with the effects of fasting in other mammals. When compared to the opposite effects observed in fasting pups, we conclude that elephant seals have evolved age‐dependent changes in fasting‐induced TH dynamics that may reflect differences in TH‐associated metabolic mechanisms.Grant Funding Source: Supported by NIH/NHLBI 442606‐RO‐29013

Maternal hyperthyroidism increases the prevalence of foregut atresias in fetal rats exposed to adriamycin

Gastrointestinal malformations such as esophageal atresia with tracheoesophageal fistula (EA/TEF) and duodenal atresia (DA) have been reported in infants born to hyperthyroid mothers or with congenital hypothyroidism. The present study aimed to test whether maternal thyroid status during embryonic foregut division has any influence on the prevalence of EA/TEF and DA in an accepted rat model of these malformations. Pregnant rats received either vehicle or 1.75 mg/kg i.p. adriamycin on gestational days 7, 8 and 9. Transient maternal hyper or hypothyroidism was induced by oral administration of levothyroxine (LT4, 50 μg/kg/day) or propylthiouracil (PTU, 2 mg/kg/day), respectively, on days 7 to 12 of gestation. Plasma cholesterol, total T3, free T4 and TSH were measured at gestational days 7, 12, and 21. At the end of gestation, the mothers were sacrificed and embryo-fetal mortality was recorded. Fetuses were dissected to determine the prevalence of esophageal and intestinal atresias. At gestational day 12, mothers treated with LT4 or PTU had hyper or hypothyroid status, respectively; plasma cholesterol levels were similar. In the adriamycin-exposed fetuses from hyperthyroid mothers, the embryonal resorption rate and the prevalence of both EA/TEF and DA were significantly higher than in the other groups; maternal hypothyroidism during the same period did not have significant effect on the prevalence of atresias. Maternal hyperthyroidism during the embryonic window corresponding to foregut cleavage increased the prevalence of both EA/TEF and duodenal atresia in fetal rats exposed to adriamycin. This suggests that maternal thyroid hormone status might be involved in the pathogenesis of foregut atresias and invites further research on this likely clinically relevant issue in humans.

The α′ subunit of β-conglycinin and the A1–5 subunits of glycinin are not essential for many hypolipidemic actions of dietary soy proteins in rats

This study examined the effects of dietary soy protein (SP) lacking different storage protein subunits and isoflavones (ISF) on the abdominal fat, blood lipids, thyroid hormones, and enzymatic activities in rats. Weanling Sprague-Dawley rats (8 males and 8 females/group) were fed diets containing either 20 % casein without or with supplemental isoflavones or alcohol-washed SP isolate or SP concentrates (SPC) prepared from 6 different soy bean lines for 8 weeks. Feeding of diets containing SPC regardless of their subunit compositions significantly lowered relative liver weights, blood total, free, and LDL cholesterol in both genders (P < 0.05) and also reduced serum free fatty acids (FFA) and abdominal fat in females (P < 0.05) compared to the casein or casein + ISF diets. Dietary SPC significantly elevated the plasma free triiodothyronine (T3) in both genders and total T3 in females compared to the casein diet (P < 0.05). The SPC lacking β-conglycinin α' and either the glycinin A1-3 or A1-5 subunits increased total T3 in males and reduced plasma enzymatic activities of creatine kinase and lactate dehydrogenase compared to casein or casein + ISF diet (P < 0.05). Soy isoflavones were mainly responsible for the hypocholesterolemic effects and increased plasma free T3, whereas reduction in FFA, abdominal fat, liver weight and increased plasma total T3 were the effects of the soy proteins. Neither the α' subunit of β-conglycinin nor the A1-5 subunits of glycinin are essential for the hypolipidemic properties of soy proteins.

Exposure to monocrotophos pesticide causes disruption of the hypothalamic–pituitary–thyroid axis in adult male goldfish (Carassius auratus)

The thyroid hormones (THs) 3,3′,5-triiodo-l-thyronine (T3) and l-thyroxine (T4) exert a wide range of biological effects on physiological processes of fish. To elucidate the thyroid disruption effects of monocrotophos (MCP), an organophosphate pesticide, on male goldfish (Carassius auratus), thyroid follicle histology, plasma total T3 (TT3), total T4 (TT4), free T3 (FT3) and free T4 levels, and the mRNA expression of indices involved in the hypothalamic–pituitary–thyroid axis (HPT axis) were examined following 21-day exposure to 0.01, 0.10 and 1.00mg/L of a 40% MCP-based pesticide. The results showed that MCP exposure induced the hyperplasia and hypertrophy of thyroid follicular epithelium and led to decreased plasma TT3 levels and TT3-to-TT4 ratios, without effect on plasma TT4 levels. Profiles of the changes in the relative abundance of deiodinase (D1, D2 and D3) transcripts were observed in the liver, brain and kidneys, during MCP exposure. An increase in the metabolism of T3, expressed as highly elevated hepatic d1 and d3 mRNA levels, might be associated with the reduction in plasma TT3 levels in both the 0.01 and 0.10mg/L groups, while in the 1.00mg/L MCP group, inhibited hepatic d2 transcripts might have also resulted in decreased TT3 levels by preventing the activation of T4 to T3. As a compensatory response to decreased T3 levels, pituitary thyroid-stimulating hormone β subunit mRNA transcription was up-regulated by the MCP pesticide. Decreases in plasma FT3 levels were also correlated with the modulation of hepatic transthyretin mRNA expression. Overall, the MCP pesticide exhibited thyroid-disrupting effects via interference with the HPT axis at multiple potential sites, resulting in disturbance of TH homeostasis.

Low-Dose Thyroxine Attenuates Autism-Associated Adverse Effects of Fetal Alcohol in Male Offspring's Social Behavior and Hippocampal Gene Expression

Fetal alcohol spectrum disorder (FASD) is characterized by neurodevelopmental anomalies manifesting in cognitive and behavioral deficits in the offspring with diverse severities. Social behavior is affected in FASD, and these deficits overlap with those of autism spectrum disorder (ASD). Identifying some of the molecular characteristics related to ASD in an animal model of FASD could ultimately provide details on the underlying molecular mechanisms of both disorders that could lead to novel treatments. Pregnant Sprague-Dawley rats received the following diets: control (C; ad libitum standard laboratory chow), nutritional control pair-fed (PF), ethanol (EtOH), or an EtOH diet supplemented with 0.3, 1.5, or 7.5mg thyroxine (T4)/l in the diet. Social behavior and memory were tested in the adult offspring. Plasma total T4, free T3 (fT3), and thyroid-stimulating hormone (TSH) levels were measured. Hippocampal expression of Gabrb3, Ube3a, Nr2b, Rasgrf1, and Dio3 were measured by RT-qPCR and protein levels of Mecp2 and Slc25a12 by Western blotting. Adult male offspring of EtOH dams showed elevated fT3 and low TSH levels. Adult male, but not female, offspring of EtOH dams exhibited social behavior and memory deficits. Expression of autism candidates, Gabrb3, Ube3a, Mecp2, and Slc25a12, was significantly increased in the hippocampus of male offspring of EtOH dams. Hippocampal Nr2b and Dio3 were also increased, while Rasgrf1 was decreased in the same population. Peripheral thyroid function, social behavioral deficits, and altered expression of the above genes were normalized by simultaneous administration of 0.3mg/l T4 in the EtOH diet. Our data suggest that social interaction deficits of FASD share molecular mechanism with ASD by showing altered hippocampal expression of several ASD candidate genes. Social interaction deficits as well as the gene expression changes in the offspring of EtOH-consuming dams can be reversed by low dose of thyroid hormone supplementation to the mothers.

Altred Fructosamine and Lipid Fractions in Subclinical Hypothyroidism

Thyroid function disorders lead to changes in the lipoprotein metabolism. To study the lipid and the glycaemic abnormalities in the subclinical hypothyroidism cases and to compare the same with the euthyroid, overt hypothyroid and the hyperthyroid subjects. Four groups, euthyroid (Group-I), hypothyroid (Group-II), subclinical hypothyroid (Group-III) and hyperthyroid (Group-IV), which consisted of 30 subjects each, of either sex, who were aged 25-55 years, underwent Fasting Plasma Glucose (FPG), fructosamine, lipid profile and total T3, T4 and TSH estimations. The subjects who were on lipid lowering or thyroid disorder drugs and known diabetics were excluded from the study. In Group-III, all the lipid fractions were comparable to those of Group-II and they were significantly deranged, as compared to those of Group-I. The fructosamine levels were significantly higher in Group-II and Group-III (p<0.05), but the subclinical hypothyroid pool had statistically lower levels than the hypothyroid pool (376.63±54.73, 587.80±65.10). In the Group-IV patients, the LDL-C levels were significantly higher as compared to those in the euthyroid pool. The fructosamine levels were significantly lower in comparison with both the euthyroid and the hypothyroid pools (both in Groups-II and III). The FPG levels were higher in all the classes of the thyroid abnormalities (subclinical hypothyroidnot significant) but within the reference range of 70-100mg/dl. Since the lipid derangement in subclinical hypothyroidism is on par with that in overt hypothyrodism, the subclinical hypothyroid cases also need to be treated similarly. The fructosamine values which are largely in excess of the FPG values, indicate a higher propensity to glycation and a decreased turnover of the proteins in the hypothyroid and the subclinical hypothyroid pools. Vice versa is true of the hyperthyroid pool. Fructosamine can be included in the thyroid work up of the patients to assess the metabolic function and the subsequent response after the initiation of the therapy.

Relationship between plasma thyroid hormones and some biochemical parameters in Iranian Sarabi calves

The thyroid gland has some important endocrine hormones that regulate basal metabolism in various tissues of domestic animals. Thyroid hormones have a central role in animals’ development and their tissue functions. In this study, the relationship between the plasma thyroxine (T4), triiodothyronine (T3), free thyroxine (fT4), free triiodothyronine (fT3), triglyceride, cholesterol, glucose, total protein, and albumin concentrations as well as albumin/globulin ratio in different ages of Iranian Sarabi calves was investigated. Blood samples were collected from the jugular vein of 47 clinically healthy calves free from internal and external parasites (grouped according to their age—1–14 days, 1–2, and 3–6 months) in early of winter. The level of thyroid hormones was determined by chemiluminescence, and other parameters were measured by spectrophotometry using commercial kits. Our data from this study indicates that there was no significant difference and correlation in all the studied parameters between age groups and sexes. But we found a significant correlation between plasma T4 and total protein (P < 0.05, r = 0.600), T4 and albumin (P < 0.05, r = 0.575), T3 and fT3 (P < 0.05, r = 0.610), T3 and total protein (P < 0.01, r = 0.725), T3 and glucose (P < 0.01, r = 0.685), and fT4 and fT3 (P < 0.05, r = 0.609) concentrations as well as between total protein and albumin/globulin ratio (P < 0.01, r = −0.783).

Efeito da administração de tiroxina sobre o peso corporal e sobre algumas características físico-químicas e histológicas do músculo Longissimus dorsi de marrãs com 70 dias de gestação

ABSTRACT The effect of the thyroxine administration on body weight and on some physicochemical and histological characteristics of the Longissimus dorsi muscle was evaluated in gilts at 70 days of gestation. Twenty middle-sisters gilts, daughters of F1 females with a ¾ Landrace X ¼ Large White, male were used. At 150 days of age, i.e., before first heat, the animals were randomly distributed into two groups: treated (n = 10) and control (n = 10). The treated group received a daily dose of 400 μ g of L-thyroxine (T4) in the diet until three days before slaughter and the control group received only diet. Before artificial insemination, blood was collected for determination of plasma total T4. The gilts were inseminated in the second estrus and slaughtered at 70 days of gestation. The initial and final body weight, daily weight gain and pH, water retention, and percentage of muscle fibers and stroma in the Longissimus dorsi muscle were studied. The means of all variables were compared by the Student t-test. Before insemination, the gilts showed clinical signs of hyperthyroidism, characterized by significant increase in plasma levels of T4, mild exophthalmos, and behavioral change characterized by aggression and agitation. There was not significant difference among groups according to the studied parameters. It was concluded that the daily administration of 400µg of thyroxine does not change the daily weight gain during the gestation, as well the pH, the water retention, and the percentage of muscle fibers and stroma of the

Effects of dietary phytoestrogens on plasma testosterone and triiodothyronine (T3) levels in male goat kids

BackgroundExposure to xenoestrogens in humans and animals has gained increasing attention due to the effects of these compounds on reproduction. The present study was undertaken to investigate the influence of low-dose dietary phytoestrogen exposure, i.e. a mixture of genistein, daidzein, biochanin A and formononetin, on the establishment of testosterone production during puberty in male goat kids.MethodsGoat kids at the age of 3 months received either a standard diet or a diet supplemented with phytoestrogens (3 - 4 mg/kg/day) for ~3 months. Plasma testosterone and total and free triiodothyronine (T3) concentrations were determined weekly. Testicular levels of testosterone and cAMP were measured at the end of the experiment. Repeated measurement analysis of variance using the MIXED procedure on the generated averages, according to the Statistical Analysis System program package (Release 6.12, 1996, SAS Institute Inc., Cary, NC, USA) was carried out.ResultsNo significant difference in plasma testosterone concentration between the groups was detected during the first 7 weeks. However, at the age of 5 months (i.e. October 1, week 8) phytoestrogen-treated animals showed significantly higher testosterone concentrations than control animals (37.5 nmol/l vs 19.1 nmol/l). This elevation was preceded by a rise in plasma total T3 that occurred on September 17 (week 6). A slightly higher concentration of free T3 was detected in the phytoestrogen group at the same time point, but it was not until October 8 and 15 (week 9 and 10) that a significant difference was found between the groups. At the termination of the experiment, testicular cAMP levels were significantly lower in goats fed a phytoestrogen-supplemented diet. Phytoestrogen-fed animals also had lower plasma and testicular testosterone concentrations, but these differences were not statistically significant.ConclusionOur findings suggest that phytoestrogens can stimulate testosterone synthesis during puberty in male goats by increasing the secretion of T3; a hormone known to stimulate Leydig cell steroidogenesis. It is possible that feedback signalling underlies the tendency towards decreased steroid production at the end of the experiment.

Biochemical severity of thyroid ectopia in congenital hypothyroidism demonstrates sexual dimorphism

A recent study suggested that sexual dimorphism affects initial thyroid function in congenital hypothyroidism (CH) but differs according to aetiology of CH. To determine if sexual dimorphism was associated with biochemical severity of CH and its aetiology in our large British population. We examined retrospectively the initial thyroid function tests of 140 infants diagnosed with CH from screening. All infants underwent Tc-pertechnetate radionuclide scans at diagnosis to establish the aetiology of CH prior to commencement of treatment. Patients were classified into athyreosis, ectopia and presumed dyshormonogenesis on the basis of thyroid scans. A comparison of males and females were made within the three aetiological groups for gestational age, birth weight, initial dose of levothyroxine (LT4), screening TSH, confirmatory plasma thyroxine (T4), confirmatory plasma TSH and age of TSH suppression. There was no significant difference between sexes for gestation, birth weight and initial treatment dose in all aetiological subgroups. In thyroid ectopia, screening TSH and confirmatory plasma TSH were significantly higher in females compared with males (P < 0.01), while confirmatory plasma T4 were significantly lower in females (P < 0.05). No difference was detected between males and females in athyreosis and dyshormonogenesis subgroups for screening TSH, confirmatory plasma TSH and total T4. Sexual dimorphism influenced the biochemical severity of thyroid ectopia in congenital hypothyroidism in our British population. However, this effect was not apparent in patients with athyreosis or dyshormonogenesis. Further advances in the molecular genetics of CH are essential to evaluate this phenomenon further.

Plasma total T3 and T4 concentrations in goats at different physiological stages, as affected by the energy intake

The effects of different concentrate levels in the diet on plasma 3-3′-5-triiodothyronine (T3) and thyroxine (T4) concentrations in does of different physiological conditions were investigated. Blood samples were taken starting in autumn from 20 goats fed hay ad libitum, during the dry period (30 days and 3 days prior to the synchronized oestrus; D1 and D2, respectively), pregnancy (week 13, week 17 and week 21 of pregnancy; P1, P2 and P3, respectively) and lactation (5 weeks and 13 weeks following parturition; L1 and L2, respectively). The control group (C, n = 10) was fed either 0.2 (in periods D1, D2 and P1) or 0.4 kg maize grain(head per day) (in P2, P3, L1 and L2). The high energy diet group (H, n = 10) was fed either 0.4 (in D1, D2 and P1) or 0.7 kg maize grain(head day) (in P2, P3, L1 and L2). Plasma total T3 concentrations were affected only by the sampling period, being significantly higher in the P1 period (0.96 ± 0.05 ng/ml) than in the dry period (0.72 ± 0.04 ng/ml) and in P3 (0.70 ± 0.02 ng/ml). In the C goats the plasma T4 concentration recorded in the P1 (65.6 ± 2.6 ng/ml) and L1 (62.8 ± 5.2 ng/ml) periods was significantly higher than that in P3 (40.2 ± 3 ng/ml). The variation in plasma T4 concentration in the H does was not significantly different throughout the different physiological stages. The decrease in plasma T3 and T4 concentrations in the second half of pregnancy in the H goats was delayed by 1 month. In addition, during the last 2 months of pregnancy, the higher concentrate diet induced higher plasma T3 (0.92 ± 0.06 ng/ml) and T4 (67.2 ± 6.6 ng/ml) concentrations when compared to the C (0.76 ± 0.04 and 45.1 ± 3.2 ng/ml for T3 and T4, respectively) group. The effect of energy intake on plasma thyroid hormone secretion during late pregnancy could be explained by a negative energy balance that usually occurs during this period. During lactation the higher energy diet had no significant effect on milk yield nor on the plasma thyroid hormone concentrations. The concentrate level of the C diet seemed to be sufficient to meet the energy requirements for milk production in these goats, as indicated also by the lack of body weight and body condition score (BCS) changes during lactation. The results of the present study highlight the relationships between thyroid activity and energy balance in the goat species. Circulating thyroid hormones represent a relevant metabolic index of the animals’ nutritional state.

Plasma total T3 and T4 concentrations in bucks as affected by photoperiod

In order to determine whether total thyroxine (T4) and 3-3′-5-triiodothyronine (T3) plasma concentrations are affected by photoperiodic changes in bucks, these hormones were assayed using RIA in samples collected weekly for a year period in Alpine and Saanen male goats exposed to natural photoperiod (46°N latitude, control group), or to artificial photoperiod alternating every 2 months (4M group) or 1 month (2M) with long days (16L:8D) and short days (8L:16D). In the control group, the thyroid hormones showed marked seasonal variation. Maximal monthly peaks were recorded at the beginning of spring (April) for plasma T4 (35.7 ± 1.8 ng/ml) and in late winter to early spring (March) for plasma T3 (0.91 ± 0.11 ng/ml)—with the lowest concentrations being recorded in October (autumn) for plasma T4 (22.8 ± 1.0 ng/ml) and in September (late summer to early autumn) for plasma T3 (0.42 ± 0.01 ng/ml). In the 4M group, T4 plasma concentrations varied with daylength ( p < 0.05), recording an overall mean concentration significantly ( p < 0.01) higher during the short days (37.3 ± 7.5 ng/ml), than during long days (32.2 ± 7.3 ng/ml) with a significant effect of sampling time within each photoperiod ( p < 0.0001). In both light-treated groups, T3 varied with photoperiod ( p < 0.0001) and time ( p < 0.0001), increasing during long days and decreasing during short days. T3 plasma concentrations (derived from peripheral monodeiodination) followed the photoperiodic changes, while it was hypothesized that the stimulatory effect of daylength on T4 (thyroid gland secretory activity) was characterized by a longer latency period and could be seen in the 4M group during the following photoperiodic treatment. It is concluded that photoperiod affects thyroid hormone plasma concentrations in male goats, since different lighting regimes resulted in different profiles of both plasma T3 and T4. Bearing in mind the pivotal role of thyroid hormones in stimulating the metabolic activity of the whole body, it is possible that the light-induced increase in circulating hormones could sustain and improve animal production. The suitability of supplementary light treatments needs to be considered.