Differences In T4 Levels Research Articles

Thyroid Hormone Changes Correlate to Combined Breast Cancer with Primary Thyroid Cancer.

Breast cancer and thyroid cancer are two prevalent malignancies in women, and a potential association between the two diseases has been suggested. This retrospective case-control study was conducted involving 97 patients with breast cancer and thyroid cancer (BC-TC group) and 97 age-matched patients with breast cancer alone (BC group). Thyroid hormone levels, including triiodothyronine (T3), thyroxine (T4), free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH), were analyzed in healthy controls, BC patients, and BC-TC patients. BC-TC patients exhibited a higher rate of estrogen receptor (ER) and progesterone receptor (PR) positivity compared to BC patients. Serum T3 levels were significantly decreased in BC and BC-TC patients compared to healthy controls. However, there was no significant difference in T3 levels between BC and BC-TC patients. Serum TSH levels were significantly higher in BC-TC patients compared to BC patients. ER positivity, PR positivity, and serum TSH levels greater than 4.45 mU/L were independent risk factors for primary thyroid cancer in breast cancer patients.

Association of Melasma with Thyroid Disorders

Melasma, a common hyperpigmentation disorder, has been a subject of increasing interest due to its potential association with thyroid disorders. This systematic review and meta-analysis aimed to assess the relationship between melasma and thyroid function indicators, including thyroid-stimulating hormone (TSH), thyroxine (T4), triiodothyronine (T3), and thyroid antibodies, particularly anti-thyroid peroxidase (anti-TPO) and antithyroglobulin antibody. A comprehensive search across multiple databases identified 39 relevant studies for analysis. The systematic review and meta-analysis were ultimately conducted based on the data extracted from these 39 selected studies. The meta-analysis revealed significant differences in thyroid function indicators between individuals with melasma and control groups. Melasma patients exhibited higher TSH levels (SMD = 0.33, 95% CI: 0.18, 0.47) and lower T4 levels (SMD = -1.50, 95% CI: -2.96, -0.04). However, no significant difference in T3 levels was observed (SMD = -0.01, 95% CI: -0.20, 0.19). Notably, the presence of anti-TPO antibodies was significantly associated with melasma (Fisher = 26.80, P = 0.020). Gender-specific analyses revealed more pronounced thyroid function differences among women with melasma, suggesting potential hormonal influences. Melasma predominantly affects women and often exhibits exacerbations during pregnancy, indicating a complex interplay between sex hormones and thyroid function in pigmentation regulation. These findings have clinical implications for dermatologists and endocrinologists. Dermatologists should consider thyroid evaluation in melasma patients, especially in cases with treatment resistance. For endocrinologists, melasma could serve as a cutaneous marker for underlying thyroid dysfunction, particularly in women. Further research is needed to elucidate the mechanisms underlying this association and its temporal aspects. Longitudinal studies could provide insights into whether thyroid ........

Impact of thermal stress on physiological, behavioural and biochemical parameters in native and crossbred goats

The present study was undertaken to investigate the association of the temperature-humidity index with physiological, biochemical and behavioural responses in Malabari, crossbred and Attappady black goats of Kerala, India. A positive correlation was noticed between in-house temperature (IT) and temperature-humidity index (THI) with respiration rates, rectal temperatures, heart rate and skin temperature levels of breeds at 2.00 PM and 5.00 PM. Biochemical and endocrines parameters, blood gases and electrolytes were analysed during the 2nd, 32nd and 60th day of the study. Alterations in physiological parameters were more significant in Malabari goats. However, a negative correlation was observed between in-house relative humidity and all physiological parameters during all the different times. Behavioural patterns were influenced by increased IT and THI and the breeds spent more time in standing position during heat stress. A significant difference was observed within the study period in the pO2, Na+, HCO3- and blood pH. A significant difference was observed between the breeds for K+, Cl- and HCO3- levels. A significantly higher glucose level on the 32nd day and a lower total cholesterol level in the latter half of the experimental period were noticed in Malabari and crossbred. Mean total protein levels of all the breeds were significantly increased on the 32nd day. Increased GGT levels were observed in the first half of the experimental period in all breeds. Higher cortisol levels in Malabari and crossbred could be estimated in the first half of the experiment. Although Malabari showed higher T3 levels on the 32nd day compared to other breeds, within the breeds no significant difference in T3 levels could be noticed. However, significantly higher T4 values were recorded on the 32nd day and 60th day only in Crossbred breeds when the IT and THI were high. Thus it has been shown that heat stress was affecting the physiology, metabolism and behaviour of breeds. The increase in respiratory rate and rectal temperature were the first signs of heat stress in these breeds. The physiological manifestations of stress were the greatest for Malabari goats and the least for Attappady black.

Correlation between abnormal thyroid function test and thyroid autoimmunity: a systematic review and meta-analysis.

This study was to analyze the correlation between abnormal thyroid function detection and thyroid autoimmune disease, so as to provide theoretical guidance for clinical diagnosis of thyroid autoimmune disease. The Chinese databases were searched with a combination of words "thyroid", "thyroid autoimmune disease", "thyroid function testing", "meta-analysis". The entire database was searched in English language databases with the search terms "thyroid", "thyroid autoimmune disease", "thyroid function test ", "meta-analysis". Review manager software was applied for meta-analysis. A total of 8 articles were finally included. 4 articles reported the T3 level, showing P=0.95, I2=0%, odds ratio (OR) =2.39, 95% confidence interval (CI): 0.79-7.25; 3 articles reported the T4 levels, showing P=0.81, I2=0%, OR =2.16, 95% CI: 0.43-10.71; and 4 articles reported the thyroid stimulating hormone (TSH) level, showing P=0.48, I2=0%, OR =3.20, 95% CI: 1.45-7.07. After a systematic review of the literature, a significant difference was found in T3 and TSH levels between patients with autoimmune thyroid disease and those with a healthy thyroid, but the difference in T4 level was not significant.

Thyroid function and immune status in perch (Perca fluviatilis) from lakes contaminated with PFASs or PCBs

The environment contains a multitude of man-made chemicals, some of which can act as endocrine disruptors (EDCs), while others can be immunotoxic. We evaluated thyroid disruption and immunotoxic effects in wild female perch (Perca fluviatilis) collected from two contaminated areas in Sweden; one site contaminated with per- and polyfluoroalkyl substances (PFASs) and two sites contaminated with polychlorinated biphenyls (PCBs), with one reference site included for each area. The hepatic mRNA expression of thyroid receptors α and β, and the thyroid hormone metabolising iodothyronine deiodinases (dio1, dio2 and dio3) were measured using real-time PCR, while the levels of thyroid hormone T3 in plasma was analysed using a radioimmunoassay. In addition, lymphocytes, granulocytes, and thrombocytes were counted microscopically. Our results showed lower levels of T3 as well as lower amounts of lymphocytes and granulocytes in perch collected from the PFAS-contaminated site compared to reference sites. In addition, expressions of mRNA coding for thyroid hormone metabolising enzymes (dio2 and dio3) and thyroid receptor α (thra) were significantly different in these fish compared to their reference site. For perch collected at the two PCB-contaminated sites, there were no significant differences in T3 levels or in expression levels of the thyroid-related genes, compared to the reference fish. Fish from one of the PCB-contaminated sites had higher levels of thrombocytes compared with both the second PCB lake and their reference lake; hence PCBs are unlikely to be the cause of this effect. The current study suggests that lifelong exposure to PFASs could affect both the thyroid hormone status and immune defence of perch in the wild.

Serum total triiodothyronine (T3) as a predictor of mortality and morbidity in critically ill patients and its correlation of predictability with acute physiology and chronic health evaluation II score: A prospective observational study.

Background:The aim is to assess the prognostic value of total T3, total T4, and thyroid-stimulating hormone among critically ill patients admitted to the medical intensive care unit (ICU) in association with mortality and its correlation with the acute physiology and chronic health evaluation II (APACHE II) score.METHODS: Our prospective observational study consists of 257 patients without known thyroid diseases admitted to the medical ICU. The baseline characteristics of the patients were recorded, including the APACHE II score and thyroid hormone levels at ICU admission. Based on the primary outcome of mortality, we analyzed the data by appropriate statistical methods. A P < 0.05 was considered significant.Results:Of the 257 patients included in the study, 47 (18.28%) succumbed to their illnesses. A significant difference in T3 levels (P < 0.001), T4 levels (P < 0.001), and APACHE II score (P < 0.001) was found between the survivors and the nonsurvivors. There was negative correlation observed between T3 and APACHE II score (r = −0.448, P < 0.001) and T4 and APACHE II score (r = −0.221, P ≤ 0.001). Multivariate logistic regression analysis determined T3 to be the only independent predictor of ICU mortality among thyroid hormones. The area under the curve (AUC) for T3 (0.811 ± 0.04) was almost equal to that of the APACHE II score (0.858 ± 0.029). The duration of ICU stay and hospital stay in patients with low T3 was significantly higher compared to patients with normal T3.Conclusion:Serum T3 is a good indicator for predicting mortality and morbidity among critically ill patients.

A Comparison Between The Effect Of Shisha And Cigarette Smoking On Thyroid Function Of Males

Studies show, that smoke may effect physiological of the thyroid gland functions, this study aim was to decide the effects of cigarette smoke or hookah smoke on thyroid function in males. Thyroid is a consider endocrine gland located under the larynx, thyroid hormones of the major are thyroxinT4, Tri-iodothyroxine T3 , and thyroid inspiring hormone TSH,. Male divided into cigarette smokeG1, hookah smoking G2,and control group G3, The results indicated that serum TSH levels were significant change low a in the G1 group than with the control group(G3), and we found the levels of TSH hormone were significant change lower P˂0.05 in the cigarette smokers compared with the control group, TSH levels were no significant P≥0.05 between the hookah smokingG2 3.6±0.004 and control group, and highly significant mean differences among two groups in the TSH levels between the G1 and G2, Our findings also indicated a significant increase in T3 or T4 serum levels in smoking, also the levels of triiodothyronine hormone (T3) were P˂0.05 (significantly higher) in the cigarette smokers 3.50±1.1 nmol/l compare with the control group G3, 0.98±0.002nmol/l,, We found also the levels of thyroxine T4 significant higher p˂0.05 than control G3 and cigarette smokers. Also the significant differences in T3 levels P˂0.05 betweenG24.01±`0.4 than G3 0.98±0.002,also we found significant differences in the T4 levels P˂0.05 between G2 140±30 compared G3 120±22, . Also we found no significant change in T3 levels P>0.05 between G1 3.50±`1.1than G2 4.01±`0.4, also we found no significant changes in T4 levels P>0.05 in G1 135±24compared G2

EVALUATION OF THYROID DISORDERS IN SUDANESE PATIENTS WITH DOWN SYNDROME

Down syndrome is the most common life compatible chromosomal disorder responsible for the majority of mental retardation and deaths in infancy and childhood. The current study intended to evaluate the thyroid disorders in Sudanese patients with Down syndrome by assessment of thyroid function tests (T3, T4 &amp; TSH) . It was descriptive case control study, carried out in Khartoum, the capital of Sudan, from March to July 2018. It included fifty (50) participants, thirty (30) of them as case group with Down syndrome and twenty (20) normal healthy subjects as control group. Their ages ranged from seven (7) to twenty eight (28) years.&#x0D; The study findings showed significant variation in TSH level with mean (2.66 ), (1.67 ) in case and control group respectively with P. value (0.001). There was also significant variation when compared children and adults mean TSH level (1.88 ),(2.59 ) with P. value of (0.03). There was insignificant differences in T3 level with mean SD(1.04 .32),(1.11 ) between case and control group respectively with P. value of (0.08) . There was also insignificant difference in T4 level with mean (6.09 ),(6.40 ) in case and control group respectively with P. value of (0.7). There were also insignificant differences in T4 and T3 levels between the age groups. As regard to the gender of the patients, there were insignificant differences of TSH, T4, and T3

Impact of thyroid status on the response to ram effect in ewes

The role of thyroid hormones on the transition to anestrous has been well established in ewes, but their possible involvement in the induction of reproductive activity remains obscure. The aim of the present study was to investigate the role of thyroid hormones in the induction of the first ovulation in relation to "ram effect" in ewes. Fourty-four ewes of the Greek Zackel mountain type breed were used. The ewes were housed separately from the rams until day 0 (entrance of rams). Blood samples were collected weekly for 4 weeks until 11 weeks after the ram entrance for the determination of thyroxin and progesterone levels. Thirty-five out of 44 ewes (group A) had a silent heat, while the rest 9 ewes (group B) exhibited a delayed estrus. Thyroxin levels rose immediately after ram entrance in animals of group A, but in group Β the increase in thyroid hormone levels was evident only after the first week. The difference in T4 levels between week 0 and 1 for ewes of group A was significantly higher than that observed for animals of group Β (p&lt;005). The pattern of progesterone release was similar between the two groups, but a two week delay in the increase of progesterone concentration was observed in animals of group Β compared to group A. It is concluded that thyroid hormones may act at the beginning of the breeding season to cause a modification in gonadotrophin secretion leading to early ovulation.

Effect of ascorbic acid on long-term cold exposure induced changes in thyroid activity in Sprague Dawley rats.

To determine the effect of ascorbic acid supplementation on long-term cold exposure induced changes in thyroid activity in Sprague-Dawley rats. Experimental study. Physiology Department of Islamic International Medical College, Rawalpindi, National Institute of Health, Islamabad and Railway Hospital, Rawalpindi, from January to December 2009. Ninety Sprague-Dawley rats were randomly divided into three groups of control, cold exposed and cold exposed along with ascorbic acid supplementation. After one month, their thyroid levels were analyzed by using chemiluminescent immunometric assay on Siemens Immulite 2000 Analyzer. After 4 weeks of cold exposure to experimental animals, the thyroid activity was raised significantly in the cold exposed group as compared to the control group (p-value for T3 difference = 0.004, T4 difference = 0.002 and TSH difference < 0.001). Supplementation with ascorbic acid in the third group normalized the thyroid hormone activity with p-value for difference in levels of T3 being 0.6661, T4 = 0.027 and TSH = 0.0028. Ascorbic acid prevented the cold induced changes in thyroid hormone levels in rodents.

Effect of Different Levels of Supplemental Yeast on Body Weight, Thyroid Hormone Metabolism and Lipid Profile of Broiler Chickens

In poultry, the benefits of probiotic supplementation on broiler performance and health have been reported. The present study examined the effect of supplemental yeast probiotic preparations on body weight, thyroid hormone metabolism and serum lipid profile in broilers. The experiment was carried out on hybrid Marshall broiler chickens (n=200). Two hundred 1-day-old chicks were randomly selected and distributed into 4 groups of 50 1-day-old chicks each (control, C; E10.5%, E21.5% and E32.0%, experimental groups). The birds were housed in an environmentally controlled poultry house with the floor covered with wood shavings. Chicks were fed commercial broiler starter diet for the first 28 days of age, followed by pelleted finisher diet from 29-42 days. Feed and water were provided ad libitum. Chickens fed 2.0% probiotic had a significantly (P<0.05) higher body weight when compared with the control group. The blood glucose concentration was significantly (P<0.05) different in the E31.5% probiotic supplemented group when compared with the control. There was highly significant (P<0.05) difference in T4 level in the E32.0% probiotic group when compared with the control. However, there was a significant difference in cholesterol concentrations observed in the experimental group supplemented with E10.5% probiotic. The concentration of triglycerides was not affected by the probiotic supplementation. Significant differences (P<0.01) were observed in HDL concentrations in all experimental groups supplemented with the probiotic when compared with the control group. In conclusion, supplementing broiler feeds with a yeast probiotic increased body weight, enhanced thyroid hormone metabolism, and decreased cholesterol and lipoproteins in broiler chickens.

The Thr92Ala 5′ Type 2 Deiodinase Gene Polymorphism Is Associated with a Delayed Triiodothyronine Secretion in Response to the Thyrotropin-Releasing Hormone–Stimulation Test: A Pharmacogenomic Study

The common Thr92Ala D2 polymorphism has been associated with changes in pituitary-thyroid axis homeostasis, but published results are conflicting. To investigate the effects of the Thr92Ala polymorphism on intrathyroidal thyroxine (T4) to triiodothyronine (T3) conversion, we designed prospective pharmacogenomic intervention aimed to detect differences in T3 levels after thyrotropin (TSH)-releasing hormone (TRH)-mediated TSH stimulation of the thyroid gland. Eighty-three healthy volunteers were screened and genotyped for the Thr92Ala polymorphism. Fifteen volunteers of each genotype (Thr/Thr, Thr/Ala, and Ala/Ala) underwent a 500 mcg intravenous TRH stimulation test with serial measurements of serum total T3 (TT3), free T4, and TSH over 180 minutes. No differences in baseline thyroid hormone levels were seen among the study groups. Compared to the Thr/Thr group, the Ala/Ala group showed a significantly lower TRH-stimulated increase in serum TT3 at 60 minutes (12.07 ± 2.67 vs. 21.07 ± 2.86 ng/dL, p = 0.029). Thr/Ala subjects showed an intermediate response. Compared to Thr/Thr subjects, the Ala/Ala group showed a blunted rate of rise in serum TT3 as measured by mean time to 50% maximum delta serum TT3 (88.42 ± 6.84 vs. 69.56 ± 6.06 minutes, p = 0.028). Subjects attained similar maximal (180 minutes) TRH-stimulated TT3 levels. TRH-stimulated TSH and free T4 levels were not significantly different among the three genotype groups. The commonly occurring Thr92Ala D2 variant is associated with a decreased rate of acute TSH-stimulated T3 release from the thyroid consistent with a decrease in intrathyroidal deiodination. These data provide a proof of concept that the Thr92Ala polymorphism is associated with subtle changes in thyroid hormone homeostasis.

5'-Deiodinase type 1 activity in liver and brain of the thyroxine-treated dystrophic hamster.

Dystrophic hamsters (DH), as well as dystrophic patients, exhibit alveolar hypoventilation (AH) and low plasma thyroid hormone levels. Thyroxine (T4) treatment of young DH retards AH development, and improves respiratory function and contractility of skeletal muscles. However, the mechanism responsible for the hypothyroidism in DH is not known. One possible cause of the hypothyroidism is reduced activity of the 5'-deiodinase enzyme system, which converts T4 to the more active triiodothyronine (T3). This study tested the above hypothesis by measuring the serum T3 and T4 levels and the activity of the enzyme type 1 5'-deiodinase (D1) in the liver and brain of normal and dystrophic hamsters before, and 8 weeks after, placebo or T4 treatment. There was no significant difference in T4 level between normal and dystrophic hamsters before or after treatment. However, the T4 level was lower in DH before treatment and 8 weeks after placebo and T4 treatment. Both in the liver and brain, D1 activity in DH was depressed compared with normal hamsters. In the liver, T4 supplementation restored enzyme activity to normal level, while in the brain there was no significant difference. The data indicate that the hypothyroidism in DH may be, in part, due to reduced activity of D1 enzyme, which could be partially reversed by T4 treatment.

Prenatal and Postnatal Impact of Perfluorooctane Sulfonate (PFOS) on Rat Development: A Cross-Foster Study on Chemical Burden and Thyroid Hormone System

Perfluorooctane sulfonate (PFOS), an environmentally persistent organic pollutant, has been reported to be transferred to the developing organisms via both placenta and breast milk. A cross-foster model was used to determine whether prenatal or postnatal exposure to PFOS alone can disturb the TH homeostasis in rat pups, and if so, which kind of exposure is a major cause of TH level alteration. Pregnant rats were fed standard laboratory rodent diet containing 0 (control) or 3.2 mg PFOS/kg throughout gestation and lactation period. On the day of birth, litters born to treated and control dams were cross-fostered, resulting in the following groups: unexposed control (CC), pups exposed only prenatally (TC), only postnatally (CT) or both prenatally and postnatally (TT). Serum and liver PFOS concentrations, serum total thyroxine (T4), total triiodothyronine (T3), reverse T3 (rT3) levels, and hepatic expression of genes involved in TH transport, metabolism, and receptors were evaluated in pups at the age of postnatal days (PNDs) 0, 7, 14, 21, or 35. PFOS body burden level in pups in group CT increased, while those in group TC dropped as they aged. Neither total T3 nor rT3 in pups was affected by PFOS exposure. Gestational exposure to PFOS alone (TC) significantly (p < 0.05) decreased T4 level in pups on PNDs 21 and 35, 20.3 and 19.4% lower than the control on the same PND, respectively. Postnatal exposure to PFOS alone (CT) also induced T4 depression on PNDs 21 and 35, 28.6 and 35.9% lower than controls, respectively. No significant difference in T4 level (p > 0.05) was observed between TC and CT on these two time points. None of the selected TH related transcripts was affected by PFOS in pups on PND 0. Only transcript level of transthyretin, TH binding protein, in group TT significantly increased to 150% of the control on PND 21. The results showed that prenatal PFOS exposure and postnatal PFOS exposure induced hypothyroxinemia in rat pups to a similar extent, which suggested that in utero PFOS exposure and postnatal PFOS accumulation, especially though maternal milk, are matters of great concern.

운동 강도의 차이가 제2형 당뇨병 환자와 비만인의 초과산소 섭취량, 안정 시 대사량 및 생화학적 변인에 미치는 영향

The purpose of this study was to evaluate the effect of various exercise intensity on Excess post exercise energy expenditure (EPEE), Resting Metabolic Rate (RMR),thyroid hormonal changes and biochemical variables in obese and NIDDM patients. The subject of the present study were divided into four groups and four periods: trained (T; n=10), control (C; n=10), obese (O; n=10) and NIDDM (N; n=10) group. And the periods were divided as follows; Resting (RE), Maximal (MA), High intensity (HI), and Low intensity (LI). There was significant difference in RMR among different intensity of exercise. in the T (p<0.05) not in the C, O, and N groups. however, there was no significant different percent body fat among all groups. In the energy expenditure, there was significant different among C, O, N groups compare to T in HIEE (high intensity exercise energy expenditure), LIEE (low intensity exercise energy expenditure), HIEEPE (high intensity exercise energy expenditure post exercise) and LIEEPE (low intensity exercise expenditure post exercise). In the hormonal level, there was significant different in T4 level in the T group at LI period and there was also significant difference in T4, Free T3, & Free T4 levels in T group at LI period, however there was no significant different in the O and N groups except LI period. In the fatigue variables, there was significant different in lactate and ammonia levels in the N group in the period of HI compare to C. The present cross-sectional study was design to investigate the relationship between exercise intensity and RMR in four groups. The focus of this investigation was to compare RMR in aerobically trained (T), control (C), obese (O) and NIDDM (N) group. The relationship among RMR, exercise intensity and percent body fat would best be investigated using Meta Lyzer 3B, MMX3B and body composition analyzer. Each subject completed measurement of percent body fat, RMR, hormone in the period of maximal oxygen uptake exercise (MA), high intensity exercise (HI), and low intensity exercise (LI). From the results, High and Low intensity of exercise, there was a trend for an increased RMR (kcal/day) in the trained groups and control group (in case of LI) not for the obese and N groups. This is best explained not by the reduced percent body fat but by the highly induced energy expenditure (during exercise and post exercise energy expenditure) and increased T4, Free T3, and Free T4 hormonal levels in the low intensity exercise for the T group and sometimes C group.

Effects of canola meal on physiological and biochemical parameters in rainbow trout (Oncorhynchus mykiss)

Rainbow trout (initial body weight 4.16 ± 0.25 g) were fed diets [crude protein 420 g kg−1; gross energy 18.7 MJ kg−1 dry matter (DM); crude fat 110 g kg−1] containing graded levels of either a canola meal (crude protein 350 g kg−1 DM) supplemented with DL-methionine as partial fish meal protein. A growth trial was conducted over 16 weeks at a water temperature of 12 ± 1 °C. At the end of the growth trial, in addition to body composition analyses, plasma tri-iodothyronine (T3) and thyroxine (T4), cholesterol and liver fatty acid composition were measured. Replacement of fish meal with canola meal (100–570 g kg−1 replacement) did not affect on growth performance. At 16th week, plasma cholesterol levels were reduced in fish fed all diets in comparison with 8th week. Plasma T4 levels were significantly higher in the canola meal-fed fish sampled after 16 weeks, but no significant differences in T3 levels were obtained (P > 0.05). Proximate compositions were affected by dietary treatments. The liver fatty acid composition reflected that of the diet with a higher level of polyunsaturated (n-6) fatty acids in fish fed diet canola meal and a higher content in n-3/n-6 ratio in fish fed diet without canola meal. These studies show that canola meal has potential to replace substantial levels of fish meal in diets for carnivorous fish without compromising performance.

Consequences of Food Restriction on Short-Term Growth Variation and on Plasma Circulating Hormones inOreochromis niloticusin Relation to Sex

In tilapia, there is a sex-related growth difference between males and females. This study tried to detect any correlation between the somatic growth and the plasma endocrine status. For this, individually marked (Floy-tags) male and female tilapia (BW 82±10 g) were either starved or fed on different daily food rations (1, 2, or 3% of the biomass) during 15 days. We have found that specific growth rates (SGR) were positively and significantly related to feeding levels. Growth hormone (GH) plasma levels tended to increase with the decrease in food levels, and thus with the decrease in growth rate. No significant correlation was found between GH levels and SGR. Triiodothyronine (T3) levels in well-fed fish were higher than those in restricted fish (0 and 1%), but no differences in thyroxine (T4) levels were observed. No significant relationship was found between plasma levels of steroid hormones and feeding ration, even though 11-ketotestosterone (11-KT) levels tended to increase with the ration in fed males. SGR were not significantly different between males and females at the same feeding level, but taken as a whole, they were significantly different in favor of males (P<0.05). There was no important difference in GH levels between the two sexes. Steroid hormones were, in general, higher in males for 11-KT and in females for 17β-estradiol (17β-E2). Males and females exhibited significant differences in T3levels (respectively 4.25±0.18 and 2.71±0.09 pmol/ml), whatever the food ration, but no significant differences in T4levels were observed except in the high-ration group. The correlation between T3levels and SGR was low but stronger in males (r2=0.21;n=90) than in females (r2=0.10;n=105). The slope of the log–log regression of T3levels with body weight was much lower in females (b=0.87) than in males (b=1.31). This relationship suggests the involvement of T3in tilapia growth and probably in the differential growth between males and females. In both males and females, a significant but low correlation was observed between T3and 11-KT levels (respectivelyr2=0.12;n=82 andr2=0.08;n=89), while no correlation was found between the levels of T3and 17β-E2. T3plasma levels were found to be the most different parameter between males and females. This hormone seemed to be involved in the control of somatic growth, and could explain the differential growth rate between males and females.

Changes in tissue thyroxine level of metamorphosing Japanese flounder Paralichthys olivaceus reared at different temperatures.

Effects of thyroid hormones and rearing temperature on Japanese flounder metamorphosis were studied by measuring tissue concentration of thyroxine (T4) by radioimmunoassay. Larvae reared at 15 or 22°C of various developmental stages were quickly frozen and stored at about -32°C until assayed. Non-detectable values of T4 were obtained for pre-metamorphic larvae at both 15 and 22°C. The T4 level increased to a maximum of 16.2ng/g during late metamorphosis, and then decreased slightly. Higher rearing temperature accelerated growth and metamorphosis and also induced earlier increase in tissue T4 levels. Comparison of larvae of similar developmental stages reared in different temperatures revealed no significant difference in T4 levels. These results indicate that thyroid hormones play an important role in Japanese flounder metamorphosis.

Measurement of T4, T3 and reverse T3 levels, resin T3 uptake, and free thyroxin index in blood from the intervillous space of the placenta, in maternal peripheral blood, and in the umbilical artery and vein of normal parturients and their conceptuses.

T4, T3, and reverse T3 (rT3) levels and the free thyroxine index were measured in blood collected from the intervillous space (IVS) after placental expulsion and compared to the values in maternal peripheral blood and in umbilical artery and umbilical vein of 21 clinically normal parturients and their conceptuses. T4 levels in maternal peripheral blood did not differ significantly from T4 levels in the IVS, but were significantly higher than those detected in umbilical vein and artery (p less than 0.05). There was no difference in T4 levels between umbilical vein and artery. The free thyroxine index was similar for the maternal compartments (maternal peripheral blood and IVS), but differed significantly from the fetal compartments (umbilical vein and umbilical artery). T3 levels in maternal peripheral blood were significantly higher than in the IVS, both of these values being significantly higher than in the fetal compartments. There was no difference in T3 levels between umbilical vein and artery. rT3 levels of maternal peripheral blood were one third that of the IVS (p less than 0.05). rT3 levels of the umbilical vein were 1.5 times higher than those of the IVS (p less than 0.05) and 5.2 times higher than those of maternal peripheral blood (p less than 0.005). No significant difference was obtained between umbilical vein and artery. The increase in rT3 and the decrease in T3 in the IVS in relation to maternal peripheral blood support the hypothesis that the placenta may preferentially convert T4 to rT3 at the expense of T3. The present data, however, do not permit the identification of the site where this conversion takes place.

Influence of oral administration of sulfamethazine on thyroid hormone levels in Fischer 344 rats.

Fischer 344 rats (810 of each sex) were divided into treatment groups and fed diets containing 0, 10, 40, 600, 1200, or 2400 ppm sulfamethazine. Serum samples were analyzed for levels of thyroid-stimulating hormone (TSH), total thyroxine (T4), total triiodothyronine (T3), and T3 uptake after 12, 18, or 24 mo of continuous dosing. There were no statistically significant differences in T3 levels or percent T3 uptake for either sex after any of the exposure periods. The serum T4 levels were lower (p less than 0.05) for females dosed at 1200 and 2400 ppm for 18 mo and for males dosed at 600, 1200, or 2400 ppm sulfamethazine for 24 mo than for those dosed at levels of 40 ppm or less. Serum TSH levels showed a general increasing trend (but not statistically significant) among animals receiving 600 ppm or more sulfamethazine. There was a significant dose-related reduction in (T3 + T4)/TSH ratio for both sexes (p less than 0.05) after 18 and 24 mo of exposure at dose levels of 600 ppm or more. A lack of response at 12 mo may have been due to the shorter treatment time. At each sacrifice period both sexes of rats fed sulfamethazine at 1200 and 2400 ppm had significantly heavier (p less than 0.05) thyroid weights than animals fed control diet. The heavier thyroid weights in the dosed animals may have resulted from increased TSH levels. The cause of reduction in serum T4 was not clearly evident. Therefore, the thyroid hormone to pituitary feedback mechanism apparently compensated for sulfamethazine effects in most animals. This would suggest that the thyroid gland was not irreversibly affected.