Hypothyroid Ones Research Articles

The influence of experimentally changed thyroid status on cognitive activity and angiogenesis in brain of female of inbred mice С3 Н-А

The study was performed using 33 virgin females of inbred mice C3H-A. The animals were randomized as follows 3:2:2. The first group was hyperthyroid (n1=15), the second hypothyroid (n2=10) and the third euthyroid (control) (n3=8). The results of individual behavior investigation as to 18 and 40 weeks of our experiment in “open field” test clarified that quantitative traces of almost whole components of cognitive activity was much higher in hyperthyroid mice as compared to other groups (control and hypothyroid ones). The cognitive behavior activity has gradually been decreasing in hypothyroid group especially in connection to burrow reflex. As to those elements of behavior which are of characteristics of emotions the results were a bit different. The emotional characteristics were more expressed in hyperthyroid group as compared to control and hypothyroid ones. The immunohistochemical investigations clearly showed that expression of vascular endothelial growth factor (VEGF) in neocortex and hyppocampus prevails in hyperthyroid mice and less expressed in animals deprived of thyroid hormones (p < 0.05). The level of glial fibrillar acidic protein (GFAP) expression was significantly lower in brain of hypothyroid animals (p < 0.05). Otherwise the level of platelet derived growth factor receptor-α (PDGF-Rα) expression was much higher in brain of hypothyroid mice (p < 0.05). Our results presented for this paper confirmed the key role of thyroid hormones in regulation of cell interaction not only for developing neural cells but also for adult central nerve system.

Does assessment of carbonic anhydrase activity support the diagnosis of various thyroid disorders

ObjectiveTo evaluate the activity of carbonic anhydrase (CA) in various thyroid disorder patients and their results were compared with euthyroid acting as a control. MethodsTwo hundred and sixty-three participants were enrolled for the present study with ages ranging from 6 months to 74 years. Among them, hypothyroid, hyperthyroid and euthyroid subjects were chosen. Twelve hours' fasting blood samples were collected from all the patients reported to Medicine Out Patients Department and assessment of CA activity was done in all the three category patients. The data from the patients and controls were compared by using the student's t-test. The values were expressed as mean±standard deviation. Microsoft Excel for Windows 2003 was used for statistical analysis. P<0.05 were considered to indicate statistical significance. ResultsThe serum levels of CA activities were observed to be higher in hyperthyroid patients compared to hypothyroid ones and the CA activity in euthyroid subjects were comparatively higher than hypothyroid subjects. It was also observed that the serum CA activity was significantly correlated with both T4 (r=0.997, P<0.001) and FT4 (r=0.590, P=0.039) values. ConclusionThough our study contains a very small sample size, as a pilot study we have demonstrated that the serum levels of CA activity is associated with the serum thyroxine levels.

The influence of experimentally changedthyroid status on cognitive activity and angiogenesis in the brain of female inbred С3Н-А mice

The study was performed using 33 virgin females of inbred C3H-A mice. The animals were randomized as follows 3 : 2 : 2. The first group was hyperthyroid (n1 = 15), the second hypothyroid (n2 = 10) and the third euthyroid (control) (n3 = 8). The results of individual behavior investigation as to 18 and 40 weeks of our experiment in “open field” test clarified that quantitative traces of almost whole components of cognitive activity was much higher in hyperthyroid mice as compared to other groups (control and hypothyroid ones). The cognitive behavior activity has gradually been decreasing in hypothyroid group especially in connection to burrow reflex. As to those elements of behavior which are of characteristics of emotions the results were a bit different. The emotional characteristics were more expressed in hyperthyroid group as compared to control and hypothyroid ones. The immunohistochemical investigations clearly showed that expression of vascular endothelial growth factor (VEGF) in neocortex and hyppocampus prevails in hyperthyroid mice and less expressed in animals deprived of thyroid hormones (p &lt; 0.05). The level of glial fibrillar acidic protein (GFAP) expression was significantly lower in brain of hypothyroid animals (p &lt; 0.05). Otherwise the level of platelet derived growth factor receptor-α (PDGF-Rα) expression was much higher in brain of hypothyroid mice (p &lt; 0.05). Our results presented for this paper confirmed the key role of thyroid hormones in regulation of cell interaction not only for developing neural cells but also for adult central nerve system.

Impacts of the coexistence of diabetes and hypothyroidism on body weight gain, leptin and various metabolic aspects in albino rats

The present study was conducted to assess the interrelationship and the influence of the coexistence of diabetes and hypothyroidism on thyroid hormone levels, insulin levels and biochemical variables related to carbohydrate, lipid and protein metabolism in addition to thyroid gland and Islets of Langerhans histological changes and antioxidant defense system. Diabetes mellitus was induced by intraperitoneal injection of streptozotocin to fasting albino rats at dose level of 45mg/kg b. w. Hypothyroidism in diabetic and normal rats was induced by adding methimazole in drinking water (0.02% w/v) for 4weeks. The obtained results revealed that hypothyroidism interacts with diabetes in a way that prevents the progress of the hyperglycemic state. This may be due to the increase in the insulin secretory response in diabetic hypothyroid than diabetic rats. Serum T3 level decreased in order in diabetic (−26.63%), hypothyroid (−61.89%) and diabetic hypothyroid (−65.69%) rats while T4 level was increased in diabetic rats and decreased in hypothyroid ones. The decrease in T3 level in diabetic animals in spite of T4 increase may be attributed to the decrease in conversion of T4 to T3 as a result of hepatic 5′-DI decreased activity. Liver glycogen content was three-fold decreased in diabetic rats and was not significantly altered in both hypothyroid and diabetic hypothyroid rats. The serum leptin level and body weight gain were decreased in diabetic and diabetic hypothyroid rats; the leptin level was more deteriorated in diabetic hypothyroid rats while body weight gain was more affected in diabetic rats. Serum triglycerides level was more increased in diabetic rats than in diabetic hypothyroid ones on one hand, while total lipids, total cholesterol, LDL-cholesterol levels as well as cardiovascular indices were more deteriorated in diabetic hypothyroid rats than diabetic ones on the other hand. Serum total protein and globulin levels were decreased in diabetic rats and were increased in hypothyroid and diabetic hypothyroid rats. Hepatic total thiols and glutathione contents and catalase and peroxidase activity were profoundly decreased in diabetic rats while they (except glutathione) were increased in hypothyroid and diabetic hypothyroid rats. In conclusion, the hypothyroidism may have a counteracting effect on the hyperglycemic state and the elevated serum T4 level as well as the deteriorated antioxidant defense system found in diabetes mellitus, but both experimentally-induced diseases may synergize in inducing more elevation of serum total lipids, total cholesterol and LDL-cholesterol and more decrease in leptin levels.

Comparative study of the effects of experimentally induced hypothyroidism and hyperthyroidism in some brain regions in albino rats

Thyroid hormones (THs) play a crucial role in the development and physiological functioning of different body organs especially the brain. Therefore, the objective of this study was to show the histopathological effects of the different thyroid states on some brain regions (cerebrum and cerebellum) and the skeletal features of their newborns during the postnatal development from the 1st to 3rd week. The female white albino rats were allocated into 3 groups as follows: the experimental hypothyroidism group is induced by 0.02% methimazole (MMI) (w/v) in drinking water, while the experimental hyperthyroidism group is performed by exogenous T4 [from 50 to 200μg/kg body weight intragastric administration beside adding 0.002% T4 (w/v) to the drinking water] from the gestation day 1 to lactation day 21 and control group which received tap water.As well, both maternal hypo- and hyperthyroidism caused some malformation and developmental defects in the cerebellar and cerebral cortex of their newborns along the duration of the experiment. These degenerative symptoms became more prominent and widely spread at the 3rd postnatal week. Concomitantly, there were some degeneration, deformation and severe growth retardation in neurons of these regions in both treated groups throughout the experimental period. Moreover, the skeletal features of these newborns were accelerated in hyperthyroid group while these maturations were delayed partially in hypothyroid ones during the examined periods. These alterations, on both treated groups, were age and dose dependent. Thus, further studies need to be done to emphasize this concept.

Apoptose, proliferação e histomorfometria do baço de ratas adultas com hipofunção tireoidiana e ovariana

Apoptosis, proliferation and histomorphometry of spleen were investigated in ovariectomized and non-ovariectomized adult Wistar rats maintained in hypothyroidism induced by daily administration of propylthiouracil (PTU) during 120 days. Two groups ovariectomized euthyroid and non-ovariectomized euthyroid were used as controls. Plasma was collected for free T4 dosage and the spleen for histomorphometry analysis, apoptosis index and the immunohistochemistry expression of caspase 3 and CDC47. Values of free T4 were lower in rats treated with PTU (p<0.05). In the hypothyroid groups there was some decrease in the spleen weight as well as the number and size of lymphoid follicles and there was some increase in the apoptotic index and the caspase 3 expression (p<0.05). However, the increase in the apoptosis index and the expression of caspase 3 in ovariectomized hypothyroid rats spleen was less accentuated than non-ovariectomized hypothyroid ones (p<0.05). The ovariectomized euthyroid group presented white pulp hyperplasia in comparison to the non-ovariectomized euthyroid group. There was no difference in the CDC47 expression between groups. It was concluded that the thyroid and ovarian hypofunction have distinct effects on the spleen and that in the hypothyroidism-hypogonadism association, the increase in the apoptosis index and in the expression of splenic caspase 3 is not as much as in isolated hypothyroidism.

Effect of thyroid state on H 2O 2 production by rat liver mitochondria

It has been suggested that activation of mitochondrial respiration by thyroid hormone results in oxidative tissue injury secondary to increased reactive oxygen species production. In order to throw light on this subject, the effects of thyroid state on O 2 consumption and H 2O 2 release by rat liver mitochondria were investigated. Hypothyroidism decreased the rates of O 2 consumption and H 2O 2 release by succinate or pyruvate/malate-supplemented mitochondria during both State 4 and State 3 respiration, whereas hyperthyroidism increased such rates. Conversely, with both substrates and during either respiration phase, the percentage of O 2 released as H 2O 2 was not significantly affected by thyroid state. On the other hand, the capacity of mitochondria to remove H 2O 2 increased by about 17% in hyperthyroid rats and decreased by about 35% in hypothyroid ones. This result indicates that the ratio between H 2O 2 production and release and so the percentage of O 2 turned into H 2O 2 instead of being reduced to water increase in the transition from hypothyroid to hyperthyroid state. In light of previous observations that mitochondrial content of cytochromes and ubiquinone also increases in such a transition, the modifications of H 2O 2 production appear to be due to a modulation by thyroid hormone of the mitochondrial content of the autoxidisable electron carriers. This view is supported by measurements of H 2O 2 release in the presence of respiratory inhibitors, which show that the thyroid state-linked changes in H 2O 2 production occur at H 2O 2 generator sites of both Complex I and Complex III.

Decrease in mitochondrial energy coupling by thyroid hormones: a physiological effect rather than a pathological hyperthyroidism consequence

The effect of the in vivo thyroid status on mitochondrial membrane potential (ΔΨ m) in isolated rat hepatocytes was studies by means of a cytofluorimetric technique and the ΔΨ m-specific probe JC-1. It is shown that the ΔΨ m level decreases in the order hypothyroid>euthyroid>hyperthyroid. Polarographic measurement of the hepatocyte respiratory rates revealed an opposite trend of values: the highest respiratory rate in hepatocytes from hyperthyroid animals, the lowest in those from hypothyroid ones. This means that mitochondrial energy coupling is highest in hypothyroid hepatocytes and lowest in hyperthyroid hepatocytes. 6-Ketocholestanol added to hepatocytes failed to counterbalance the uncoupling effect of thyroid hormones on ΔΨ m and respiration rate. Under the same conditions, 6-ketocholestanol appeared to be effective in recoupling of respiration uncoupled by low concentrations of the artificial protonophore FCCP. The mechanism and possible physiological functions of the thyroid hormone-induced decrease in mitochondrial energy coupling are discussed.

Effects of Thyroid Status on Cold-Adaptive Thermogenesis in Brandt's Vole, Microtus brandti

Hyper- and hypothyroidism were induced by subcutaneous injection of thyroxine and by oral administration of methimazol in Brandt's voles. The effects of the two treatments on metabolic thermogenesis at 25 degrees C and 4 degrees C were investigated. The level of resting metabolic rate was closely related to thyroid status: high in the hyperthyroid case and low in the hypothyroid case. However, no increase in resting metabolic rate occurred in either case during further cold acclimation. Hyperthyroidism resulted in an increased nonshivering thermogenesis, which was much enhanced by lower temperature, but hypothyroidism led to a suppressed nonshivering thermogenesis in the cold. The state-4 and state-3 respirations and the activities of cytochrome-c oxidase of liver mitochondria were elevated in hyperthyroid animals but attenuated in hypothyroid ones. However, these levels were scarcely changed after further cold acclimation. Both hyperthyroidism and cold acclimation induced the recruitment of brown adipose tissue, but brown adipose tissue was different biochemically in the two cases: in hyperthyroidism, the total protein was reduced, while fat content increased; in cold acclimation, the total and mitochondrial proteins were increased. However, in hypothyroid voles, the normal adaptive changes in brown adipose tissue were impaired in further cold acclimation. The activity of cytochromec oxidase in brown adipose tissue was increased by hyperthyroidism and enhanced in further cold. In contrast, its activity was inhibited in hypothyroid animals, though activated to some extent in cold. These results demonstrate that normal thyroid function is essential for the cold-induced increase of resting metabolic rate and nonshivering thermogenesis and that there is a synergism between thyroid hormone and cold acclimation in the regulation of nonshivering thermogenesis in Brandt's vole. In addition, the blunted response of brown adipocytes to the cold may be the cytological mechanism for the suppressed nonshivering thermogenesis found with hypothyroidism.

Direct thyroid hormone signalling via ADP-ribosylation controls mitochondrial nucleotide transport and membrane leakiness by changing the conformation of the adenine nucleotide transporter

Addition of triiodothyronine at 10 pM in vitro to hypothyroid rat liver mitochondria doubles the rate of the adenine nucleotide transporter at low ADP concentrations. Nicotinamide abolishes this effect in parallel with its inhibition of the ADP-ribosylation of an inner membrane protein identical in size to the transporter. Nicotinamide also renders euthyroid preparations indistinguishable from hypothyroid ones. A mechanism is offered to explain these findings in which it is proposed that the adenine nucleotide transporter is a true allosteric protein and that its covalent modification by ADP-ribosylation increases the stability of the less favoured externally-facing C-conformation and thus increases the proportion of transporters in this orientation: although the C-conformation is significantly more leaky to cations than the tight matrix-facing M-conformation, this enhances ADP import. This model is shown to offer an explanation not only for the transport effects of T 3 but also for those of oxidative stress and ADP-ribosylation inhibitors on Ca 2+, H + and K + transfer across the mitochondrial inner membrane. Ca 2+ at 30 nM appears to stabilize the M-conformation of the transporter by a mechanism other than ADP-ribosylation.

Incorporation of D 3H glucosamine to the adult and developing cochlear tectorial membrane of normal and hypothyroid rats

The uptake of d- 3H-glucosamine by the developing cochlea of normal and hypothyroid rats was examined using light microscopic radioautography. During postnatal development, normal and hypothyroid rat cochleas exhibited a layer of radiolabelling in the tectorial membrane (TM). This layer first appeared in the TM region which covers the spiral limbus and the Kölliker's organ (KO), then progressively reached the apical part of the TM covering the organ of Corti. Radiolabelling was significantly greater in hypothyroid than in normal cochleas. These findings suggests that the enormous size reached by the TM in the congenital hypothyroidism could be related to an increase of epithelial secretion, at least for carbohydrates. It also suggests that TM, in normal and hypothyroid cochleas, could be formed during development by the addition of successive layers. Older layers could he displaced upwards by the new ones. Cochleas of normal young adult rats, treated with d- 3H-glucosamine, showed a very scarce and diffuse radiolabelling. Cochleas of hypothyroid young adult rats exhibited a thickened and distorted TM, which incorporated a significant amount of carbohydrates. These results suggest that TM secretion is highly reduced in young adult normal animals, while in young adult hypothyroid ones it is still active. During cochlear maturation, thyroxine seems to be neccesary, not only for the synthesis of normal glycoproteins (as suggested by previous reports), but also for the control of glycoprotein secretion.

Thyroid control of contractile function and calcium handling in neonatal rat heart.

Newborn rats were rendered hyperthyroid (daily subcutaneous injections of L-triiodothyronine, 10 micrograms 100 g-1 body weight) or hypothyroid (0.05% 6-n-propyl-2-thiouracil in drinking water to nursing mothers) during the first 3 weeks of postnatal life. Compared with the euthyroid group, hyperthyroidism resulted in: (1) cardiac enlargement with right ventricular preponderance, (2) increased cardiac contractile function, (3) increased Ca2+ uptake by the sarcoplasmic reticulum (SR), (4) decreased sensitivity to the negative inotropic effect of verapamil and (5) greater inhibition of contractile function by ryanodine. Hypothyroidism generally resulted in opposite changes. The data suggest that the development of the heart and its contractile function during early postnatal life depends on the plasma level of thyroid hormones. In particular, the relative contribution of the SR and sarcolemmal Ca2+ transport to the control of cardiac contractility seems to be markedly affected by altered thyroid states. The postnatal maturation of the SR function is accelerated in hyperthyroidism but retarded in hypothyroidism. Consequently, hyperthyroid hearts appear to be less dependent and hypothyroid ones more dependent on trans-sarcolemmal Ca2+ fluxes when compared with age-matched euthyroid animals.

Lectin staining of saccharides in the normal and hypothyroid developing organ of Corti

Lectin staining has been used to detect mono- and oligosaccharides in normal and hypothyroid developing organs of Corti in the rat. Eight developmental stages were studied (1, 5, 8, 10, 15, 20, 50 and 60 days after birth). Congenital hypothyroidism was induced by oral administration of propylthyouracil to pregnant rats. Labelling of the tectorial membrane with 3 lectins, Ulex europaeus agglutinin-I (UEA-I), Lens culinaris agglutinin (LCA) and Ricinus communis agglutinin-I (RCA-I) showed no significant differences between normal and hypothyroid animals. Staining with peanut agglutinin (PNA) showed that the hypothyroid adult tectorial membrane (but not the normal one) possesses the disaccharide galactose+ N-acetyl galactosamine. Phaseolus vulgaris agglutinin-L (PHA-L) labels the whole tectorial membrane in both groups of animals, but the staining is more intense in the hypothyroid one for a narrow band of oligosaccharide located just between the tectorial membrane and the underlying organ of Kölliker. Both soybean agglutinin (SBA) and succinylated wheat germ agglutinin (WGA) stain the tectorial membrane as well as the cytoplasm of the cells constituting the inner portion of the organ of Kölliker; this latter feature disappears in the normal animals about the 8th postnatal day, but it is abnormally preserved until the 60th postnatal day in the hypothyroid ones. In the adult hypothyroid animals, 3 of the lectins (LCA, PHA-L and WGA) stain extracellular conglomerates located under the synaptic pole of the outer hair cells.

Biological half-time of tritiated water: Comparison of hyperthyroid and hypothyroid patients

The half-time values of tritiated water were explored in eleven hyperthyroid patients and in two hypothyroid ones. For reasons of comparability the numbers are expressed in days per square meter (d/m 2) of body surface. Against the estimated 5.4 d/m 2 in normal subjects, the hyperthyroids reflected 3.9 ± 0.66 and the two determinations on hypothyroids were 6.42 and 7.13, respectively. During the study neither diagnostic nor therapeutic procedures were ever postponed. The half-time values are not representative of extreme conditions in hyper- or hypothyroids, but are sufficiently clear to indicate well-defined differences from normal people. The total exposure to radiation for the exploratory procedure was minimal, estimated at less than 12 mrem for the normal standard man.

Effects of thyroid function on submaxillary gland sensitivity to autonomic nervous drugs.

The effect of changes in thyroid function on the action of autonomic drugs upon the secretion of saliva by the submaxillary glands was studied in male Wistar rats. Hyperthyroidism was induced by the sc administration every 12 h of 10 micrograms/100 g bw of L-triiodothyronine; hypothyroidism was induced by surgical thyroidectomy 2 weeks before the experiments. The dose-response curves to increasing doses of isoprenaline, norepinephrine or methacholine showed in hyperthyroid animals increased salivary secretion, while in hypothyroid animals the dose-response to the drug was reduced. The threshold dose for isoprenaline was reduced in hyperthyroid animals and increased in hypothyroid ones. The threshold dose for norepinephrine did not change in hyperthyroid or hypothyroid animals while that for metacholine was decreased in hyperthyroid ones. When norepinephrine was given to alpha-blocked animals (with phentolamine) the difference in the dose-response curves between hyperthyroid and control animals was increased. But when norepinephrine was given to beta-blocked animals (with propranolol) the difference between the dose-response curves of hyperthyroid and control animals disappeared. The results above presented show that the sensitivity of the submaxillary salivary glands of rats to some adrenergic and cholinergic drugs was altered by the thyroid hormone. The effect was greater in the responses mediated by beta receptors. The structural changes in these glands may have some role in these effects.

Effect of a 2 mg thyroxine bolus on the hypophyseal-thyroid axis (author's transl)

The effect of a single dose of 2 mg L-thyroxine on central and peripheral parameters of the hypophyseal-thyroid axis was studied on ten euthyroid and ten hypothyroid patients, and ten with euthyroid goitre. Without the occurrence of hyperthyroid symptoms, the T4 serum level was raised for five days in the euthyroid group, for 11 days in the hypothyroid ones. During this time the T3 serum level did not alter. Suppression of iodine uptake by the thyroid and TSH secretion of the hypophysis persisted longer, both for basal and TRH-stimulated liberation, than the substitution effect. Even when the T4 bolus has to be at a higher total T4 dose for the same therapeutic effect than with daily small single doses, it is a comparable alternative to present-day forms of treatment. It is of particular advantage where there are medical reasons for widely spaced drug intake or rapid normalisation of the T4 serum level is deemed desirable.

Quantitative study of Purkinje cell perikaryon synaptogenesis. Effects of thyroid hormones and of heat value restriction of food intake on synaptic densities evolution

Hyper-and hypothyroidism repercussions on axosomatic synatogenesis of Purkinje cell perikaryon evolution were studied by electron microscopy on 7-,14-, 21-, and 35-day-old rats. Normal adult animals were compared with adult ones made hypothyroid until they were 35 days old. Also, heat value restriction of food intake effects were compared with hypothyroid ones at 14 and 35 days. By 7 days, Basket cell (CC) axons and Purkinje cell (CP) axon collaterals synaptic endings had not acquired entirely their adult morphological characteristics, but it was possible to identify them. In normal animals, general synaptic density (DSG) and corrected general synaptic density (DSGC) increased from 7 to 35 days, at which stage these parameters reached their definitive values. General synaptic density on somatic spines (DSGE), specific density of climbing fibers (DSS.FG) and their relative DSS decreased markedly from 7 to 35 days, at which stage all these values were nullified. DSS.CP increased from 7 to 35 days, at which stage it reached its definitive value, while relative DSS of these endings reached a maximum by day 21, then decreased until it reached its definitive value on day 35. Hyperthyroidism led to an increase of DSG and DSGC by day 14. Then these parameters were markedly decreased on day 35. DSS. FG were increased at 7 days. Afterward, its decrease as well as that of relative DSS was accelerated without advancing markedly the age at which FG did not establish a synapse on the CP soma anymore. It put to 14 days instead of 21, the stage at which DSS.CC and relative DSS if these endings reached their maximum. From this stage it led to a decreased DSS.CC but did not bring a DSS.CP or a relative DSS of these synaptic endings noticeable change. On the contrary, hypothyroidism decreased DSG and DSGC under normal. It slackened the rate of DSS.FG and of their relative DSS decrease. It maintained DSS.CC, relative DSS.CC and DS.CP lower than normal. But after 21 days, hypothyroidism increased the relative DSS.CP value. Furthermore, it led to the temporary establishment of synapses between Basket cell axons and somatic processes still present in hyperthyroid animals. Heat value restriction of food intake did not considerably changes these parameters at the studied stages. These findings were discussed according to the recent data of synaptogenesis in the cerebellum of mutant mice and in the rat Purkinje cells cultivated in the absence of afferent systems.

Effects of thyroid hormones and heat value restriction of food intake on the glial surrounding and soma development of Purkinje cell

Hyper- and hypothyroidism repercussions on soma, nucleus and cytoplasm increases were studied by electron microscopy on 7-, 14-, 21-, and 35-day-old rats. Adult normal animals were compared with adult ones made hypothyroid until they were 35 days old. Also heat value restriction of food intake effects were compared with hypothyroid ones at 14 and 35 days.

Simple screening test for the evaluation of thyroid function: Experience with two in-vitro [ 131I]thyroid function tests based on resin uptake and sephadex gel filtration

A modification of the [ 131I]tri-iodothyronine (T 3) resin uptake test was investigated. A simple, fast and convenient method was elaborated, eliminating several time-consuming steps in the procedure, such as pre-incubation of the sample, preweighing of resin, cumbersome washing procedure, furthermore choosing convenient temperature conditions (handling at room temperature, incubation at 37°) and limiting the incubation time and the number of radioactivity measurements needed. The test can be carried out in a routine isotope laboratory, without special equipment. The results of the test were compared with a Sephadex gel filtration T 3 test and, in the case of suspected thyroid disorders, also with the protein-bound iodine (PBI) and the [ 131I]thyroid uptake test in vitro. With each test (resin uptake and gel filtration), most patients can be classified correctly as euthyroid, hyperthyroid and hypothyroid ones, according to the clinical diagnosis. However, values in the hypothyroid range are found during pregnancy and under the influence of oral contraceptives, whereas gross abnormalities in serum protein pattern can give rise to values in the hyperthyroid range.

Response of rat atrium to propranolol and catecholamines in various states of thyroid action.

AbstractThe effect of propranolol on spontaneous beating, and the response of this to adrenaiinc and noradrenaline, was studied in hypothyroid, euthyroid and thyroxine treated isolated atrium of the rat hcart. A significant negative chronotropic effect was noted in thyroxinized preparations; in other groups this change was less significant. The inotropic property remained unchangcd in control conditions. A propranolol dose of 1 μg/ml blocked the positive chronotropic effect of adrenaline and noradrenaline completely in euthyroid and thyroxinized atria and partially in the hypothyroid ones. A competitive antagonism was observed between propranolol and catecholainines in the various preparations when contraction force and mechanical output werr measured. Thc positive inotropic effect of adrenaline and noradrenaline was highest in the hypothyroid and lowest in thr thyroxinized series. Only quantitative differences were ohserved in the responses of the atria to propranolol and catecholaminrs in various states of thyroid action.