Secretion Of Triiodothyronine Research Articles

Can Ashwagandha Benefit the Endocrine System?-A Review.

Withania somnifera, also known as Ashwagandha, has been used in traditional medicine for thousands of years. Due to the wide range of its activities, there has been interest in its possible beneficial effects on the human body. It is proved that, among others, Ashwagandha has anti-stress, anti-inflammatory, antimicrobial, anti-cancer, anti-diabetic, anti-obesity, cardioprotective, and hypolipidemic properties. Particularly interesting are its properties reported in the field of psychiatry and neurology: in Alzheimer's disease, Parkinson's disease, multiple sclerosis, depression, bipolar disorder, insomnia, anxiety disorders and many others. The aim of this review is to find and summarize the effect that Ashwagandha root extract has on the endocrine system and hormones. The multitude of active substances and the wide hormonal problems faced by modern society sparked our interest in the topic of Ashwagandha's impact on this system. In this work, we also attempted to draw conclusions as to whether W. somnifera can help normalize the functions of the human endocrine system in the future. The search mainly included research published in the years 2010-2023. The results of the research show that Ashwagandha can have a positive effect on the functioning of the endocrine system, including improving the secretory function of the thyroid gland, normalizing adrenal activity, and multidirectional improvement on functioning of the reproductive system. The main mechanism of action in the latter appears to be based on the hypothalamus-pituitary-adrenal (HPA) axis, as a decrease in cortisol levels and an increase in hormones such as luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in men were found, which results in stress level reduction and improvement in fertility. In turn, other studies prove that active substances from W. somnifera, acting on the body, cause an increase in the secretion of triiodothyronine (T3) and thyroxine (T4) by the thyroid gland and a subsequent decrease in the level of thyroid-stimulating hormone (TSH) in accordance with the hypothalamus-pituitary-thyroid (HPT) axis. In light of these findings, it is clear that Ashwagandha holds significant promise as a natural remedy for various health concerns, especially those related to the endocrine system. Future research may provide new insights into its mechanisms of action and expand its applications in both traditional and modern medicine. The safety and toxicity of Ashwagandha also remain important issues, which may affect its potential use in specific patient groups.

The impact of spirulina grown on wastewater on the functional status of the thyroid gland on the background experimental diabetes

The researched biopreparation has a beneficial effect on the processes of hormone synthesis in the body and presents biostimulatory effects on the β-cells of the islets of Langerhans in the endocrine pancreas, simultaneously increasing insulin, thyroxine and triiodothyronine secretion, thus maintaining metabolic homeostasis in the body. The investigations carried out highlighted the positive aspects of the biopreparation on the endocrine glands investigated against the background of experimental diabetes.

Thermal comfort of Nelore (Bos indicus) and Canchim (Bos taurus x Bos indicus) bulls kept in an integrated crop-livestock-forestry system in a tropical climate

CONTEXTClimate change presents challenges for livestock productivity and animal health. Thus, management strategies to mitigate the effects of the global temperature increase on livestock production have become progressively relevant. However, the use of integrated crop-livestock-forestry systems to optimize the beef cattle thermal balance has not been examined more deeply. OBJECTIVEThe study aimed to evaluate the microclimate in a non-shaded pasture system (NS) and in an integrated crop-livestock-forestry system (ICLF) and its influence on thermoregulatory and endocrine responses of zebu and composite bulls, during different climatic seasons. METHODSThe experiment was carried out in a tropical region, São Carlos-SP, Brazil (21°57′42″S, 47°50′28″W). Nelore (Bos indicus) and Canchim (5/8 Bos taurus x 3/8 Bos indicus) bulls were equally allocated in a non-shaded system (NS; n = 32) or in an integrated crop-livestock-forestry system (ICLF; n = 32). The animals were monthly evaluated and the data were analyzed using a GLM Model. Means were compared using Tukey test (P < 0.05). RESULTS AND CONCLUSIONSThe ICLF system reduced the air temperature (−0.6 °C; P = 0.0010), the Black Globe Temperature and Humidity Index-BGHI (−3.8; P < 0.0001), and the Radiant Thermal Load (−104 W/m2; P < 0.0001) compared to the NS system. The infrared thermograms of NS bulls were characterized by higher temperatures on the surface of the back and in the trunk, during Autumn and Winter (P < 0.05). In addition, NS bulls presented higher respiratory rate (RR: 35.85 ± 0.88 vs 31.97 ± 0.88 breaths/min; P = 0.0210) and internal body temperature (BT: 39.54 ± 0.05 vs 39.35 ± 0.05 °C; P = 0.0057) during Autumn. There was a significant reduction in cortisol concentration (−12.13 ng/mL; P < 0.05) in both systems throughout the experiment. Nelore bulls had lower RR and BT, lower mean concentration of cortisol, and higher secretion of triiodothyronine than Canchim bulls. The ICLF system was effective in mitigating the microclimate of pastures due to the action of natural shading, providing greater thermal comfort, especially for composite animals, and favored the maintenance of homeothermy in the bulls. SIGNIFICANCEThis thesis has provided a deeper insight into the physiological mechanisms involved in the thermoregulation of cattle raised in integrated crop-livestock-forestry systems. The insights gained from this study may be of assistance to indicate ICLF as a suitable option for increasing animal welfare in tropical climates.

Triiodothyronine, DHEAS/cortisol index and daily oscillations of hormones as markers of adaptation to occupational loads in the Arctic: results of hormonal status study in firefighters-rescuers of EMERCOM of Russia

Relevance. Considering that prolonged stress of adaptive mechanisms is associated with an increase in the risk of developing somatic pathology, it is relevant to search for laboratory markers that allow assessing the adaptive status of men working in the Arctic and exposed to the combined effects of occupational stress factors and “polar stress”.Intention. To substantiate directions of scientific search for laboratory markers of adaptation to occupational loads in the Arctic.Methodology. A laboratory examination was performed on 74 practically healthy firefighters-rescuers from 22 to 49 years old, working in the Arctic zone of the Russian Federation. Those examined were divided into groups depending on the conditions of occupational activity, as well as triiodothyronine levels, the adaptive androgen dehydroepiandrosterone sulfate (DHEAS) / cortisol index and the cortisol morning/cortisol evening ratio. The results of the hormonal status study were evaluated.Results and Discussion. Significant differences in triiodothyronine levels were revealed between the groups of local and visiting firefighters-rescuers, with no difference in age and concentrations of thyroid-stimulating hormone and free thyroxine.Firefighters-rescuers who were local residents of the Arctic and had low levels of triiodothyronine tended to a relative androgen deficiency. In firefighters-rescuers with preserved adaptive reserves, DHEAS / cortisol index increased with increasing workload in terms of the number of emergency response trips. In rescuers with HEAS / cortisol index &lt; 2.1, there was no such correlation, and higher index values correlated with a more pronounced rhythm of the daily secretion of triiodothyronine and free thyroxine. In the group with the most pronounced daily rhythm of cortisol secretion, a physiological increase in thyroidstimulating hormone concentration was determined in the evening hours along with uniform prolactin secretion throughout the day. A group with a smoother rhythm of cortisol secretion tended to increased evening secretion of prolactin and smoothened rhythm of thyroid-stimulating hormone production.Conclusion. The data obtained are consistent with current ideas about the polysystemic adaptive response, suggest joint activation of the adrenal and pituitary-thyroid mechanisms of adaptation to occupational loads in the Arctic and indicate the necessity of further study and application of the DHEAS / cortisol index and triiodothyronine, as well as daily oscillations of thyroid hormones, thyroid-stimulating hormone and prolactin as markers of adaptation.

Effect of elevated carbon dioxide on chicken eggs during the early and late incubation periods

Carbon dioxide (CO2) is always maintained at ambient levels by ventilation in commercial egg incubators. However, elevated CO2 levels during the early and late periods have been reported to improve the quality of chicks and shorten the hatch window. This study investigated the effect of precise CO2 supplementation during the early and late periods of incubation on embryo growth and incubation performance by developing and using a CO2 supplementation system to increase the CO2 level in an experimental egg incubator. The CO2 level was maintained at 1% in the early period (from the beginning to the 10th day of incubation, E0–E10) and in the late period (from internal pipping (IP) to the 21st day of incubation (E21), IP–E21) in an incubator for the treatment group, whereas the CO2 level was maintained at the ambient level in the other incubators for the control group. A comparative assessment of embryonic development, hatching characteristics, and hormone and nutrient levels was conducted for each trial. The experiment comprised three trials, with 300 Jing Hong No. 1 breeding eggs in each incubator. The elevated CO2 treatment significantly shortened the chick hatching time (H0) by 4 h (P < 0.05) and the hatch window by 3 h (P < 0.05) without affecting hatchability, chick weight at 1 d of age, brooding period, or quality score. At external pipping (EP), the heart weight, intestinal weight, relative intestinal weight, and relative heart weight in the treatment group were significantly higher than those in the control group (P < 0.05). In addition, the embryonic intestine, relative intestine, and relative heart weights of the newly hatched chicks in the treatment group were significantly higher than those in the control group (P < 0.05) at H0. The treatment significantly increased the concentration of corticosterone in the embryonic plasma during the period from IP to EP (P < 0.05), promoted the secretion of triiodothyronine and tetraiodothyronine (P < 0.05), and increased the glycogen content of the embryonic liver on E21 (P < 0.05). This result indicates that elevated CO2 (1%) during the early and late periods of incubation accelerated embryonic organ development and shortened the chick hatching time and hatch window without affecting hatchability or hatchling quality, which can be explained by the synergistic functions of the secretion of plasma corticosterone and thyroid hormones and the accumulation of liver glycogen between the early and late periods of incubation.

Triiodothyronine secretion in early thyroid failure: The adaptive response of central feedforward control.

Defined by thyroid-pituitary feedback control, clinical diagnosis of hypothyroidism and hyperthyroidism has become synonymous with TSH measurement. We combined in silico analysis and in vivo data to explore the central influences on thyroidal T3 production. A system of five coupled first-order nonlinear parameterised ordinary differential equations (ODEs) is used to model the feedback control of TSH and TRH by thyroid hormones together with the feedforward control of thyroidal T3 secretion and enzymatic T4-T3 conversion. Dependencies of the stable equilibrium solutions of this ODE system, that is the homeostasis of the underlying physiological process, on the system parameters were investigated whether they accounted for clinical observations. During the modelled transition to hypothyroidism, central control imposed an increasing influence in maintaining serum FT3 levels, compared to peripheral conversion efficiency. Numerical continuation analysis revealed dependencies of T3 production on different elements of TSH feedforward control. While T4-T3 conversion provided the main T3 source in euthyroidism, this was overtaken by increasing glandular T3 secretion when thyroid reserve declined. The computational results were in good agreement with data from untreated patients with autoimmune thyroiditis. Dependencies revealed in the expression of control differ in thyroid health and disease, using a physiologically based mathematical model of combined feedback-feedforward control of the hypothalamic-pituitary-thyroid regulation. Strong T3-protective mechanisms of the control system emerge with declining thyroid function, when glandular T3 secretion becomes increasingly influential over conversion efficiency. This has wide-ranging implications for the utility of TSH in clinical decision-making.

Stress induced cortisol release depresses the secretion of triiodothyronine in patients with anterior wall myocardial infarction

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

Respostas de frangos de corte criados sob estresse por calor

Para avaliar a influência do estresse por calor por até 72 horas, e o possível efeito acumulativo do estresse sobre as respostas fisiológicas de frangos de corte criados sob condições simuladas de ondas de calor, 500 frangos de corte machos, da linhagem Cobb, foram criados em duas câmaras climáticas equipadas com sistemas de aquecimento e refrigeração, por até 45 dias. Metade das aves foram criadas sob conforto térmico (ajustado de acordo com o ideal para cada idade) e as demais aves foram submetidas a ondas de calor (32 °C ± 0,5 °C por até 72 horas) em três idades (com início aos 21, 35 e 42 dias de idade). No início de cada simulação de onda de calor e após 24, 48 e 72 horas de exposição ao calor, foram avaliados parâmetros fisiológicos como temperatura retal e frequência respiratória. Além disso foram coletadas amostras de sangue para determinação de níveis hormonais (T3 e T4) e hematócrito. O aumento da frequência respiratória das aves foi verificado após 24 horas de exposição a altas temperaturas nas três ondas de calor simuladas. Durante a terceira onda de calor não houve variação da temperatura retal. A temperatura ambiente não influenciou o valor do hematócrito e os níveis de hormônios tireoidianos T3 e T4. Submeter aves a períodos de estresse por calor agudo intermitente, como durante a simulação de ondas de calor, influencia a frequência respiratória e a temperatura retal dos frangos de corte, evidenciando o consequente efeito do estresse por calor sobre o metabolismo das aves e o equilíbrio térmico corporal. As ondas de calor não afetam a secreção de tri-iodotironina e tiroxina, e a porcentagem de glóbulos vermelhos.

The Allele Distribution for the rs7250346 SNP in SLC5A5 among Saudis

Background: The sodium/iodide cotransporter solute carrier family 5 member 5 (SLC5A5) is found in the basolateral cell membrane of thyroid follicular epithelial cells as a sodium iodide symporter. It helps in the secretion of triiodothyronine (T3) and tetraiodothyronine (T4). Polymorphisms in SLC5A5 result in hypothyroidism. The aim of the study is to estimate the frequency of rs7250346, a single nucleotide polymorphism (SNP) associated with thyroid disease, in a Saudi population and to compare it to other populations. Methods: Two hundred and forty Saudi patients from King Faisal Specialist Hospital and Research Centre provided samples for the genetic analysis. Samples were genotyped for target SNPs by real time polymerase chain reaction (PCR), and the resultant rs7250346 frequency in the Saudi population was compared to other populations using HapMap. Results: Out of the 240 Saudi samples, 64% had C genotype and 35% had G genotype in the rs7250346. Conclusion: The Saudi frequency of the rs7250346 SNP of SLC5A5 differs from that of European, Chinese, Japanese, or Sub-Saharan populations in HapMap (http://hapmap.org).

The effect of different dietary levels of rapeseed meal on growth performance, carcass traits, and meat quality in turkeys

The objective of this study was to determine the effect of different dietary levels of low-glucosinolate rapeseed meal (RSM) on growth performance, blood thyroid hormone concentration, carcass traits, and chemical composition, physicochemical properties, and fatty acid profile of breast meat in growing turkeys. The experiment lasted for 21 wk. Large White BIG-6 turkeys were fed isoenergetic and isonitrogenous diets containing 0, 60, 120, and 180 g/kg of RSM. Each experimental group was comprised of 7 replicates/pen of 28 birds each. There was no effect of graded levels of RSM on final BW. An increase in the inclusion rate of RSM was followed by a linear increase in feed conversion ratio, which was significantly higher (P < 0.05) in the group fed 180 g/kg of RSM. The blood levels of free triiodothyronine decreased significantly (P < 0.05) regardless of the dietary level of RSM. No significant changes in the carcass dressing percentage or the meat fat content were observed. Significant differences were found in the fatty acid composition and physicochemical properties of breast meat. The concentrations of margaroleic acid and saturated fatty acids, including myristic and palmitic acid, in meat from male turkeys fed 120 and 180 g/kg of RSM decreased linearly; whereas the levels of oleic acid and polyunsaturated fatty acids, including linoleic and linolenic acid (an n-3 fatty acid), increased linearly. An increase in RSM content of the diets was accompanied by the unfavorable changes in selected functional properties of meat, including a significant increase in drip loss in groups fed 120 g/kg of RSM (from 1.85 to 2.38%) and 180 g/kg of RSM (from 1.85 to 3.02%) and a decrease in Warner-Bratzler shear force values in turkeys fed 180 g/kg of RSM (from 19.1 to 15.8 N). The results suggest that the quality of turkey meat could be affected by impaired triiodothyronine secretion caused by dietary RSM.

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.

Weight regain after Roux-en-Y: A significant 20% complication related to PYY

ObjectiveRoux-en-Y gastric bypass (RYGB) produces rapid and dramatic weight loss in very heavy obese patients. Up to 20% cannot sustain their weight loss beyond 2 to 3 y after surgery. MethodsTo identify putative etiologic factors producing post-RYGB weight regain, a literature survey of metabolic changes in very obese and a review of our diet-induced obese RYGB rat model data was done. ResultsWeight regain suggests an imbalance in physiologic mechanisms regulating appetite and metabolic rate. Weight regain occurred in 25% of our rats, produced by return to presurgical energy intake levels. The 75% of rats that sustained weight loss secreted a significantly larger amount of peptide YY (PYY) while suppressing leptin secretion; those that failed were unable to develop or sustain a sufficiently large plasma PYY:leptin ratio. Metabolic consequences of this failure included reversal of initial postsurgical increases in peripheral fatty acid oxidation, anorexigenic activity in the hypothalamic arcuate nucleus and paraventricular nucleus, and the expression of uncoupling protein-2 in adipose tissues, and decreases in hepatic lipogenesis, free tri-iodothyronine secretion, expression of orexigenic activity in the arcuate nucleus and paraventricular nucleus, expression of adenosine monophosphate kinase in adipose tissues, skeletal muscle mitochondrial mass, and endocannabinoid content and appetite. ConclusionWeight regain after RYGB occurs in approximately 20% of patients and constitutes a serious complication. Weight regain–promoting consequences are attributed to a failure to sustain elevated plasma PYY concentrations, indicating that combining RYGB with pharmacologic stimulation of PYY secretion in patients after RYGB who exhibit inadequate PYY concentration may increase long-term success of surgical weight reduction in morbidly obese adults.

Action of Electric Stimulation and Captopril in Nociception and 3,5,3′‐Triiodothyronine Secretion in Mice

Transcutaneous electric nerve stimulation (TENS) analgesic effect is produced by β‐endorphin release which interacts with captopril, a drug used for arterial hypertension treatment that affects thyroid hormone secretion, mainly 3,5,3′‐triiodothyronine (T3). To study a correlation between TENS (9 Hz × 30 min), captopril and T3, Mus musculus mice received nociceptive stimulation (writhe‐induced model) and were treated with captopril (1 mg/kg) and TENS and the T3 serum level was evaluated. As a result, T3 serum level rose slightly after TENS application and captopril separately but increased more after captopril alone. In addition, the antinociceptive effect produced by electric stimulation was enhanced by captopril with a high statistical significance (p < 0.001). Additionally, the TENS–captopril treatment increased T3 serum level to values 117.7% higher than control groups, reinforcing the supposed link between neuroelectric stimulation, captopril, and T3 secretion.

Pregnancy, parturition, and lactation in hypophyseal stalk-transected beef heifers

Progesterone secretion is crucial for maintaining pregnancy to parturition in mammalian species, and in cattle the corpus luteum is the primary source of this hormone. This study determined the roles of prolactin (PRL), growth hormone (GH) and luteinizing hormone (LH) in the luteotropic process in beef heifers hypophyseal stalk-transected (HST, n=7) or sham operated (sham operated controls, SOC, n=9) during midgestation. The main finding was that endogenous PRL and GH maintained progesterone secretion in HST heifers in a similar manner to that in SOC throughout pregnancy. Serum PRL averaged 37 vs 187 and GH 2 vs 4 ng/ml in HST heifers compared with SOC, whereas LH abruptly decreased to undetectable levels after HST compared with a modest 0.4 ng/ml in SOC heifers. The second finding was that parturition and lactation occurred in HST heifers with calf delivery induced to occur at the same time as SOC. Milk production in HST animals was severely limited, and postpartum estrus obliterated compared with SOC. The suckling stimulus sustained milk ejection in HST heifers in spite of diminished PRL, GH, thyroid stimulating hormone, thyroxine and tri-iodothyronine secretion. The results suggest that PRL, GH and possibly placental lactogen are luteotropic during pregnancy in cattle.

Effect of okadaic acid and calyculin-A, two protein phosphatase inhibitors, on thyrotropin-stimulated triiodothyronine secretion in cultured sheep thyroid cells.

We have studied the effect of two protein phosphatase inhibitors on thyrotropin (TSH)-stimulated triiodothyronine (T3) production by sheep thyroid cells grown in primary culture. Incubation of sheep thyrocytes with okadaic acid (OA) and calyculin-A (CL-A), two potent inhibitors of type 1 (PP1) and type 2A (PP2A) protein phosphatases, resulted in an increase of TSH-stimulated T3 production. This effect was detected using concentrations as low as 0.1 pM with OA and 1 fM with CL-A. An inhibitory effect on T3 production, due to cellular death, was observed with 6 nM OA and 1 nM CL-A. In the absence of TSH, OA or CL-A had no effect on T3 production by thyrocytes. Forskoline (10 microM), an activator of adenylate cyclase, increased the basal and TSH-stimulated T3 release by sheep thyroid cells; this effect was increased by OA in cells grown in the basal state but not in the presence of TSH. These results suggest that the marine toxins OA and CL-A, two potent inhibitors of PP-1 and PP-2A, have significant stimulatory effects on T3 secretion promoted by TSH and FK. These observations indicate that these proteins could be important mediators of thyroid hormone production.

Tumor necrosis factor-α decreases thyrotropin-induced 5′-deiodinase activity in FRTL-5 thyroid cells

Tumor necrosis factor-alpha (TNF-alpha) exerts various effects on many cell types. Acute administration of TNF-alpha to rats decrease hepatic 5'-deiodinase activity (5'D-I) and TNF-alpha has been implicated in the pathogenesis of the low triiodothyronine syndrome in non-thyroidal illness in humans. The thyroid, liver and kidney are rich in 5'D-I. Unlike hepatic and renal 5'D-I, thyroid 5'D-I is regulated by thyrotropin. We have investigated the effects of TNF-alpha on 5'D-I in FRTL-5 cells, a cultured rat thyroid follicular cell line. Tumor necrosis factor-alpha did not significantly affect basal 5'D-I but thyrotropin markedly increased 5'D-I (p < 0.001). This TSH-induced increase in 5'D-I was attenuated by TNF-alpha in a dose-dependent manner (p < 0.001). Enzyme kinetic analysis demonstrated that thyrotropin increased 5'D-I by increasing Vmax (p < 0.01) without significantly affecting Km. Likewise, TNF-alpha decreased the thyrotropin-induced 5'D-I by decreasing Vmax (p < 0.05) but not Km. The effect of TNF-alpha on thyrotropin-induced 5'D-I in FRTL-5 cells is probably mediated through post-thyrotropin-induced generation of cyclic adenosine monophosphate (cAMP) because TNF-alpha inhibited both dibutyryl cAMP (p < 0.001) and forskolin (p < 0.001)-induced increases in 5'D-I without affecting cAMP generation stimulated by thyrotropin. In conclusion, we have demonstrated that TNF-alpha inhibits thyrotropin-induced 5'D-I activity in FRTL-5 cells by pathways distal to the generation of cAMP and that TNF-alpha may play a role in the modulation of the production of triiodothyronine by the thyroid gland. (ABSTRACT TRUNCATED AT 250 WORDS)

Normal Circulating Triiodothyronine Concentrations are Maintained despite Severe Hypothyroidism in Growing Pigs Fed Rapeseed Presscake Meal

Experiments were designed to study effects of dietary rapeseed presscake meal on the thyroid and on the liver 5'-monodeiodinase activity in growing pigs. Animals were fed rapeseed presscake meal (15% in the ration) of 0-varieties (containing relatively high amounts of glucosinolates and goitrin) or a control diet (soybean meal instead of rapeseed presscake meal) without or with thyroxine added to feed. Food intake and average daily gain were comparable because pigs were pair-fed. Serum thiocyanate concentration was significantly greater in pigs fed rapeseed presscake meal. Pigs fed rapeseed presscake meal developed hypothyroidism. Serum free thyroxine concentrations in rapeseed presscake meal-fed pigs were significantly lower than in controls, normal in thyroxine-supplemented pigs fed rapeseed presscake meal and significantly above normal in thyroxine-supplemented controls. Serum free triiodothyronine concentrations were not significantly influenced by rapeseed presscake meal feeding or thyroxine supplementation. Liver weight and total DNA content in pigs fed rapeseed presscake meal were higher than in controls but were not significantly affected by thyroxine feeding. Hepatic 5'-monodeiodinase activity on a protein basis was lower in pigs fed rapeseed presscake meal and was not normalized by thyroxine supplementation. However, in whole liver, because of greater liver mass, 5'-monodeiodinase activity in pigs fed rapeseed presscake meal was similar to that in controls. The data indicate that serum free triiodothyronine concentrations in pigs fed rapeseed presscake meal could be maintained in the physiological range, probably because of enhanced triiodothyronine secretion and sufficient extrathyroidal thyroxine to triiodothyronine conversion.

Nitric oxide stimulates cyclic GMP in human thyrocytes.

Sodium nitroprusside spontaneously breaks down in solution to produce the vasodilator nitric oxide. In many cell types, this stimulates the cytosolic form of the enzyme guanylate cyclase, resulting in the elevation of cyclic GMP (cGMP). We have investigated the effect of sodium nitroprusside on the generation of cGMP in primary human thyrocytes and the SV40-transfected human thyroid cell line SGHTL-189. A dose-dependent increase in cGMP was obtained and the maximum response was observed with concentrations above 10 microM sodium nitroprusside in both cell types. Methylene blue (50 microM) had no significant effect on basal cGMP production but inhibited the effect of sodium nitroprusside at all concentrations tested, thus demonstrating that the effect was due to nitric oxide. Sodium nitroprusside had no effect on cyclic AMP (cAMP) production in these cells. TSH at 100 and 1000 microU/ml significantly stimulated the production of cAMP, but not that of cGMP, in primary human thyrocytes. Sodium nitroprusside had no significant effect on basal or TSH-stimulated triiodothyronine secretion in primary human thyrocytes. Forskolin (10 microM) significantly stimulated cAMP production in both primary thyrocytes and SGHTL-189 cells. Although forskolin had no significant effect on basal cGMP production, sodium nitroprusside-stimulated cGMP production was significantly reduced by forskolin. However, this inhibitory effect was not related to the production of cAMP.

The Mood-Elevating Effects of Sleep Deprivation in Depression-Reply

In Reply. —In depressed patients, it is clear that sleep deprivation alters both their physiological and psychological states. Biological models assume that changes in the former mediate effects of sleep deprivation on the latter. Dr Germine makes a parallel assumption when he talks about medication playing the role of preventing resurfacing of painful affects. Psychodynamic constructs, like those proposed by Germine, are intuitively easier to link to the subjective changes experienced by depressed patients after sleep deprivation, but they are not easily accessible to experimental testing. Biological mechanisms are more accessible, and for this reason, they have been the principal focus of experimental investigation in recent years. This is why I emphasized the biological component of the sleep deprivation response in my brief and selective review. Some biological explanations, such as increased triiodothyronine secretion and rapid eye movement sleep deprivation, seem cogent, because they link sleep deprivation with other established

Decreased thyroidal triiodothyronine secretion in patients with anorexia nervosa: influence of weight recovery

Basal thyroxin (T4), triiodothyronine (T3), and thyrotropin (TSH) concentrations were significantly lower before weight recovery in 10 patients with anorexia nervosa (AN) than they were in control subjects. After weight recovery, basal T4 and TSH levels were unchanged and significantly lower in AN patients than in control subjects. Basal T3 concentrations increased significantly after weight gain: however, concentrations remained lower than those in the control subjects. The maximum increase in T3 and T3 net secretory response to thyrotropin-releasing hormone (TRH), obtained before and after weight recovery, appeared significantly lower than that in control subjects: however, the increases in TSH responses were not different from those of control subjects. Thus, low T3 concentrations in AN patients may be due not only to impaired peripheral conversion of T4 to T3 associated with the altered nutritional state, but also to decreased thyroidal T3 secretion in response to endogenous TSH, which is indicative of hypothalamic-pituitary-thyroidal dysfunction.