Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Hyperthyroidism”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,297 records · Page 72Linked to original sources
PubMed1990

Catecholamine-thyroid hormone interactions and the cardiovascular manifestations of hyperthyroidism.

The spectrum of classic symptoms of hyperthyroidism suggests that in addition to the effects of increased thyroid hormone, affecting various organ systems, there is also a hyperadrenergic state. Despite this clinical impression, direct measures of serum levels of catecholamines and their urinary metabolites demonstrate values that are equal to or less than normal. In contrast, the hypothyroid patient who clinically manifests signs of decreased adrenergic stimulation can be expected to have increased levels of epinephrine, norepinephrine, and its metabolites. This review discusses possible mechanisms to explain this seeming paradox. Treatment of hyperthyroidism includes the rapid reversal of many of the adrenergic symptoms with use of beta-blocking drugs. Return to a clinically and chemically euthyroid state, however, requires antithyroid therapy accomplished over a longer period of time. A knowledge of the interaction of the cardiovascular and extracardiovascular manifestations of hyperthyroidism and the role of the adrenergic nervous system is important in the rational management of these patients.

Catecholamines↗
PubMed1980

Influence of hyperthyroidism on the superprecipitation response and Ca2+-sensitivity of natural actomyosin in cardiac and skeletal muscle.

In cardiac natural actomyosin prepared from hyperthyroid rabbits, the time of onset of the superprecipitation response was shortened by 58% and the rate of response was increased 4-fold compared with euthyroid animals. However, Ca2+-sensitivity of cardiac natural actomyosin prepared from either euthyroid or hyperthyroid rabbits was not changed over the range of 10(-7) to 6.6 . 10(-5) M free Ca2+ concentrations. Skeletal natural actomyosin prepared from either euthyroid or hyperthyroid rabbits showed a far higher Ca2+-sensitivity than cardiac natural actomyosin, but there was no difference in either time of onset or rate of superprecipitation response.

Actomyosin↗
PubMed1988

Effect of hyperthyroidism on the transport of pyruvate in rat-heart mitochondria.

A comparative study of the transport of pyruvate in heart mitochondria from normal and triiodothyronine-treated rats has been carried out. It has been found that the rate of carrier-mediated (alpha-cyanocinnamate-sensitive) pyruvate uptake is significantly enhanced in mitochondria from triiodothyronine-treated rats as compared with mitochondria from control rats. The kinetic parameters of the pyruvate uptake indicate that only the Vmax of this process is enhanced whilst there is no change in the Km value. The enhanced rate of pyruvate uptake is not dependent on the increase of the transmembrane delta pH value (both mitochondria from normal and triiodothyronine-treated rats exhibit the same delta pH value) neither does it depend on the increase of the pyruvate carrier molecules (titration of these last with alpha-cyanocinnamate gives the same total number of binding sites). the pyruvate-dependent oxygen uptake is stimulated by 35-40% in mitochondria from hyperthyroid rats when compared with mitochondria from control rats. There is, however, no difference in either the respiratory control ratios or in the ADP/O ratios between these two types of mitochondria. The heart mitochondrial phospholipid composition is altered significantly in hyperthyroid rats; in particular, negatively charged phospholipid such as cardiolipin and phosphatidylserine were found to increase by more than 50%. Minor alterations were found in the pattern of fatty acids with an increase of 20:4/18:2 ratio. It is suggested that the changes in the kinetic parameters of pyruvate transport in mitochondria from hyperthyroid rats involve hormone-mediated changes in the lipid composition of the mitochondrial membranes which in turn modulate the activity of the pyruvate carrier.

Animals↗
PubMed1984

Thyroid epididymal relationship. II. Influence of hyperthyroidism on epididymal lipids.

The influence of experimentally induced hyperthyroidism on the lipid composition of the caput and cauda epididymides has been studied in pubertal and adult rats. Thyroxine treatment did not alter the major lipid classes in the epididymis. However, regional and age-related fluctuations in the concentration of mono-, di- and triacylglycerols have been observed. While the diacylglycerols increase, mono- and triacylglycerols were found to decrease, suggesting an inverse relationship between these fractions. Among the phospholipid fractions, phosphatidylcholine and phosphatidylethanolamine were reduced. The changes in epididymal lipid profiles give an indication that the epididymis may be yet another site responsible for fertility disturbances in hyperthyroid males. The withdrawal of thyroxine from hyperthyroid animals returned the epididymal lipid profiles to normal levels. This indicates that the effects of thyroxine in the epididymis are temporary and reversible following thyroxine withdrawal.

Animals↗
PubMed1995

Expression of enkephalin and dynorphin precursor mRNAs in brain areas of hypo-and hyperthyroid rat: effect of kainic acid injection.

An abnormal thyroid status induces morphological and neurochemical modifications in the adult brain. In this study we have analyzed the expression of enkephalin (ENK) and dynorphin (DYN) precursor mRNAs by means of in situ hybridization in the brain of hypothyroid and hyperthyroid rats. The influence of thyroid hormones on kainic acid (KA)-induced expression of ENK and DYN mRNAs in the granule cells of the dentate gyrus was also studied. Our results can be summarized as follows: (1) hypothyroidism induces an up-regulation of ENK mRNA in the granule cells of the dentate gyrus and layers V/VI of the cingulate cortex and of DYN mRNA in the granule cells of the dentate gyrus; (2) the up-regulation of ENK mRNA expression in the granule cells induced by KA is not modified by altered thyroid status; (3) in contrast, the KA injection fails to up-regulate DYN precursor mRNA expression in the granule cells of the rostral dentate gyrus of the hypothyroid rats; (4) injection of KA in hyperthyroid rats increases the expression of DYN mRNA in the granule dentate gyrus more than in euthyroid rats. The present results suggest that thyroid hormones exert an inhibitory control of expression of ENK and DYN mRNAs in selected brain areas. This effect could be directly mediated though the thyroid hormone nuclear receptor or could be secondary to changes in glutamatergic transmission in the dentate gyrus, as suggested by the profound alteration of the KA-induced expression of DYN mRNA in the dentate gyrus of hypo-and hyperthyroid rats.

Animals↗
PubMed1993

Thyroxine type II 5'-deiodinase activity in pineal and Harderian gland is enhanced by hypothyroidism but is independent of serum thyroxine concentrations during hyperthyroidism.

1. This paper studies the effect of thyroid status on 5'-D activity in pineal gland, Harderian gland, brown adipose tissue (BAT), pituitary gland, brain frontal cortex (BFC), and cerebellum. 2. Hypothyroidism clearly increased diurnal 5'-D activity in Harderian gland, BAT, pituitary gland, BFC, and cerebellum. In pineal gland, diurnal values of 5'-D activity were not affected by hypothyroidism. 3. Hypothyroidism in adult rats clearly enhanced nocturnal increase of 5'-D activity in pineal and Harderian gland. Congenital hypothyroidism also enhanced the nocturnal increase of 5'-D activity in pineal gland. 4. Hyperthyroidism inhibited 5'-D activity in pituitary gland, BFC, and cerebellum. A small inhibition, although significant, was found in BAT. 5. In pineal and Harderian gland, hyperthyroidism did not inhibit either the basal diurnal values of the enzyme or the nocturnal increase of its activity. 6. Results suggest that, in tissues where 5'D-activity is regulated by adrenergic mechanisms, mostly pineal gland and Harderian gland, the enzyme activity is independent of serum T4 concentrations during hyperthyroidism.

Adipose Tissue, Brown↗
PubMed1983

Effect of 131I on the anemia of hyperthyroidism.

Data from the National Thyrotoxicosis Therapy Follow-Up Study (NTTFS) are presented here to document the existence of anemia in hyperthyroidism, a mild and reversible anemia that is simultaneously ameliorated with reversal of the hyperthyroid state. Among 20,600 women entered into the NTTF study with no previous history of hematological disorders, the prevalence of anemia was found to range from 10-15%, appearing to be higher in those selected for treatment with 131I when compared to those selected for surgery. An attempt is made to verify the recent hypothesis that thyroid hormone levels in the supraphysiologic range may suppress erythrogenesis. Two statistically significant regression models are consistent with a hypothesis of thyrotoxic bone marrow suppression. However, both associations are weak enough to suggest that some other physiologic improvement underlies the amelioration of anemia when hyperthyroidism is reversed. The degree of improvement in hematological status is similar for women in both treatment groups. Among 4464 women for whom serial hematological tests are obtained, over 3/4 of anemic patients are no longer anemic after an average 6.2 yr of follow-up. Clinicians are reassured that radioactive iodine exposure causes no further insult to the bone marrow, no matter what the cumulative dosage. The highly fractionated low dose bone marrow exposures to radiation account for the minimal hematological risks of 131I treatment.

Anemia↗
PubMedDate not supplied

Mechanisms altered beta-adrenergic responsiveness in the hyperthyroid and hypothyroid turkey erythrocyte.

Studies on the relationship between thyroid hormone and the beta-adrenergic catecholamines have been carried out in the turkey erythrocyte. Conditions of thyroid hormone excess and deficiency were examined with respect to their effects on the beta receptor itself, as well as to their effects on associated biochemical and physiological indices of beta receptor function, including agonist stimulated adenylate cyclase activity, cellular cyclic AMP generation, and catecholamine-induced stimulation of potassium ion influx. Erythrocytes obtained from hypothyroid turkeys showed a marked (approximately 50%) reduction in beta receptor number without any change in receptor affinity for agonists or antagonists. Catecholamine-sensitive adenylate cyclase activity and cellular cyclic AMP levels were similarly reduced. The sensitivity of these cells to agonist-stimulated potassium influx was significantly decreased, but maximal agonist-stimulated transport rate was unchanged. Analysis of the quantitative relationship between beta receptor number, agonist concentration, and level of catecholamine-stimulated potassium influx indicates that, at any given absolute level of receptor occupancy, the level of agonist-stimulated potassium influx is identical in hypothyroid and normal erythrocytes, and that the diminished physiological sensitivity of the hypothyroid cell is attributable in its entirety to a reduction in beta receptor number per se. The results obtained in the hyperthyroid turkey erythrocyte were strikingly different. Here, beta receptor number, binding affinity for agonists and antagonists, catecholamine-sensitive adenylate cyclase activity, and maximal cyclic AMP levels were all unchanged. In contrast, maximal agonist-stimulated potassium ion transport was markedly reduced, while the concentration of isoproterenol required for half-maximal stimulation was only slightly increased. Analysis of the relationship between beta receptor number, agonist concentration, and catecholamine-stimulated potassium influx rate indicates that, at all absolute levels of beta receptor occupancy, the stimulation of monovalent cation influx is markedly blunted in the hyperthyroid cell. In contrast to the findings in the hypothyroid cell, where decreased physiologic sensitivity to catecholamines is directly attributable to a reduction in beta receptor number, the primary abnormality responsible for diminished catecholamine responsiveness in the hyperthyroid cell would appear to be located at a point "distal" to the beta receptor itself.

Adenylyl Cyclases↗
PubMed1976

Plasma catecholamine concentrations in hyperthyroidism and hypothyroidism.

Using a modification of the fluorometric method of Anton and Sayre, we have measured the plasma epinephrine (E) and norepinephrine (NE) concentrations in patients with thyroid dysfunction. There was no significant difference in plasma E in hyperthyroid or hypothyroid subjects, the values being similar to those observed in normal subjects. There was a striking relationship between age and plasma NE in the euthyroid individuals (r = 0.685, p less than 0.001, n = 41). Observed plasma NE concentrations were similar in control subjects (21.05 +/- 1.6 ng/100 ml; mean +/- SEM) and hyperthyroid patients (22.33+/- 2.0 ng/100 ml). However, plasma NE was significantly increased in hypothyroidism (35.46 +/- 3.9 ng/100 ml; p less than 0.01) and remained statistically different when the age factor was excluded (31.31 +/- 2.67 ng/100 ml; p less than 0.025). There was no correlation between plasma NE and serum thyroxine (T4), free thyroxine (FT4), or triiodothyronine (T3), in any of the three groups studied. These data indicate that hyperthyroidism is accompanied by normal plasma NE concentrations and that hypothyroidism is associated with significantly increased plasma NE concentrations, possible in an attempt to compensate for the lack of thyroid hormones.

Age Factors↗
PubMed1987

Metabolism of plasma fibronectin in rabbits with experimental hyperthyroidism and hypothyroidism.

We previously reported that the concentration of plasma fibronectin (pFN) is increased in patients with hyperthyroidism and decreased in those with hypothyroidism. In this work, labeled pFN was given intravenously to euthyroid, hyperthyroid, and hypothyroid rabbits to examine its metabolism in states of thyroid dysfunction. In euthyroid rabbits, the serum concentration of thyroxine (T4) was 2.94 +/- 0.59 micrograms/dL, and that of pFN was 24.2 +/- 1.2 mg/dL. With 125I-FN as tracer, the half life was estimated as 72.8 +/- 2.6 hours, the fractional catabolic rate (FCR) as 2.08 +/- 0.07%/h, the rate of synthesis (SR) as 3.84 +/- 0.20 mg/kg/day and j1/j2 (the ratio of the exchange coefficients between intravascular and extravascular compartments) of pFN as 0.295 +/- 0.051. With 3H-FN as tracer, these values were not significantly different. In hyperthyroid rabbits, obtained by treatment with I-thyroxine, the serum T4 concentration was increased to 5.73 +/- 1.58 micrograms/dL and the pFN concentration to 29.6 +/- 2.2 mg/dL. In these animals, the half life of pFN was shortened to 59.8 +/- 1.0 hour, the FCR was slightly increased to 3.07 +/- 0.52%/h and the SR was greatly increased to 7.13 +/- 1.17 mg/kg/d. In hypothyroid rabbits, obtained by treatment with methylthiouracil, the serum T4 and pFN levels were reduced to 1.50 +/- 0.36 micrograms/dL and to 20.7 +/- 1.7 mg/dL, respectively, the FCR and SR were also decreased to 1.39 +/- 0.04%/h and 2.26 +/- 0.14 mg/kg/d, respectively. The values of j1/j2 did not significantly change during this work.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effect of short- and long-term experimental hyperthyroidism on plasma glucose level and insulin secretion during an intravenous glucose load and on insulin binding, insulin receptor kinase activity, and insulin action in adipose tissue.

Glucose disposal, insulin secretion, and insulin action in adipose tissue were measured in rats treated for 10 or 30 days with high doses of thyroxine (T4). Acutely induced hyperthyroidism produced a high rate of glucose disposal after an intravenous glucose tolerance test (IVGTT), accompanied by a high glucose-stimulated insulin secretion. In addition, in these rats the following phenomena were observed: (1) high insulin binding to isolated adipocytes due to an increase in the insulin receptor number; (2) high insulin binding to partially purified fat insulin receptors; (3) normal tyrosine kinase activity of fat insulin receptors; and (4) high insulin action in isolated adipocytes, such as glucose transport and lipogenesis. Chronically induced hyperthyroidism produced high rates of glucose disposal after an IVGTT, accompanied by an increase of basal and glucose-stimulated insulin secretion. These rats showed (1) normal insulin binding to either isolated adipocytes or partially purified insulin receptors; (2) normal tyrosine kinase activity of fat insulin receptors; (3) normal insulin action in isolated adipocytes. In conclusion, exogenous hyperthyroidism induced an increase in glucose disposal, probably due in part to high insulin secretion. In short-term T4-treated rats an additional increase of insulin action in adipocytes was also observed.

Adipose Tissue↗
PubMed1981

Acute hyperthyroidism during pregnancy: a case report and critical analysis.

A rare case of acute hyperthyroidism during pregnancy is described and the management is discussed. Prompt subtotal thyroidectomy may be superior to the use of antithyroid drugs in particular circumstances. Fetal outcome of hyperthyroid mothers is discussed in the light of recent long-term follow-up studies and immunogenetic data. Women considered to be hyperthyroid are at high-risk for obstetrical and neonatal problems: early diagnosis of this condition is of paramount importance.

Adult↗
PubMed1985

The transition from a fixed ratio to a fixed interval schedule of reinforcement in hypo and hyperthyroid rats.

The modification of behavior caused by hypo and hyperthyroidism were studied when the schedule of reinforcement was changed from a fixed ratio to a fixed interval. The conditions of hypo and hyperthyroidism were obtained with a chronic administration of methimazole and of 1-thyroxine. The level of the modifications of thyroid activity was determined by evaluation of the basal metabolic rate and of the plasma levels of T4. Hyperthyroidism caused no modification of the rat behaviour. A difficulty in adapting to the new experimental situation (learning) was found in hypothyroidism. This effect is evident in high hypothyroidism. In low hypothyroidism a depression of the rat behaviour may interfere with the modification of the learning process.

Animals↗
PubMed1990

Neonatal hyperthyroidism enhances growth of the heart but not of skeletal muscle.

Comparison of growth and biochemical development of the heart and skeletal muscle (gastrocnemius) in normal rats and those treated with triiodothyronine (T3) (0.1 micrograms/g bw, s.c.) daily, from birth until weaning (day 25), revealed that hyperthyroidism selectively enhanced cardiac growth as shown by marked increases in total content (per heart) of DNA (25%), RNA (22%), protein (31%), and myofibrillar protein (30%), as well as the activity of myosin ATPase (11-20%). On the contrary, the above parameters were significantly decreased in the skeletal muscle of hyperthyroid rats as was body weight. Termination of T3 treatment on day 25 led to resumption of rapid body growth which was not complete even by day 90. Cardiac growth decelerated in rehabilitating rats, however, resulting in final reduction of all growth parameters, except DNA content which was equal in 90-day control and rehabilitated animals. Muscle growth in terms of DNA and RNA content failed to respond to rehabilitation and continued to be lower than control animals while protein synthesis was relatively enhanced. It is concluded that neonatal hyperthyroidism markedly enhanced growth of the heart but not of skeletal muscle. This condition not only inhibited growth of the muscle during the T3 treatment period but also led to permanently reduced DNA content and other growth parameters even two months after discontinuation of treatment.

Animals↗
PubMed1986

Thyroid-stimulating hormone pituitary adenomas and hyperthyroidism.

Six cases of hyperthyroidism secondary to thyroid-stimulating hormone (TSH)-hypersecreting pituitary adenomas are presented (five females and one male). Hyperthyroidism presenting with diffuse goiter was associated with hyperprolactinemia in three cases. Elevation of triiodothyronine (T3) and thyroxine (T4) plasma levels was associated with TSH levels ranging between 2 and 2,000 microU/mL. Polytomography and computed tomography scanning with coronal views revealed four invasive and two enclosed tumors. Two patients underwent transfrontal operations, four underwent transsphenoidal operations, and one underwent both. Two cases of enclosed adenoma were cured primarily by a transsphenoidal approach without additional pituitary deficit. In four cases of invasive adenomas, operations and radiation therapy resulted in three failures and one cure. In cases presenting with hyperthyroidism and detectable TSH, early neuroradiological studies are indicated, as biological cure can be achieved by the transsphenoidal approach. Early treatment is also advocated because of the tendency for these tumors to become invasive (four out of six tumors).

Adenoma↗
PubMed1993

Effects of perinatal hypo- and hyperthyroidism on the levels of nerve growth factor and its low-affinity receptor in cerebellum.

Deficits or excesses of thyroid hormones during critical periods of mammalian cerebellar development can lead to profound biochemical and morphological abnormalities in this system. The goal of this study was to investigate the effects of perinatal hypo- and hyperthyroidism on the ontogeny of nerve growth factor (NGF) and its low-affinity receptor (p75NGFR) in the rat cerebellum. The concentration of NGF and of p75NGFR immunoreactivity (IR) were measured, several days after birth, in cerebella of rats which had received propylthiouracil (PTU) or thyroxine. NGF concentration was markedly enhanced only on postnatal day 2 (P2) in hyperthyroid rats, whereas in hypothyroid (PTU-treated) rats NGF values were similar to age-matched controls. These observations suggest that thyroid hormone affects NGF synthesis during early periods of cerebellar development. In Purkinje cells of control animals, p75NGFR IR peaked at P10. In hypothyroid rats, the expression of p75NGFR was retarded, peaking at P15, whereas in hyperthyroid rats it was advanced, peaking at P8. The increased p75NGFR IR found in Purkinje cell bodies and the delayed disappearance of p75NGFR IR from the external granular layer of hypothyroid rats suggest different roles for thyroid hormone in the developing cerebellum. We conclude that p75NGFR and NGF are independently regulated by thyroid hormone during critical periods of cerebellar development. The effect of thyroid hormone deficiency on p75NGFR content in Purkinje cells may involve complex mechanisms such as impaired efficiency of axonal transport.

Animals↗
PubMed1988

Prolapse of the mitral valve in hyperthyroid patients in Saudi Arabia.

Eighty-two patients (60 females and 22 males) who were under treatment for hyperthyroidism at the King Saud University affiliated hospitals in Riyadh, Saudi Arabia, were evaluated by M-mode and cross-sectional echocardiography for the presence of mitral valve prolapse. Sixty-seven patients (51 females and 16 males) had diffuse toxic goitre while 15 of them (9 females and 6 males) had nodular toxic goitre. The overall frequency of prolapse was 37.8% (31 of 82) and the frequency was similar for both sexes, being 38.3% in females and 36.3% in males. Prolapse was associated with both diffuse toxic goitre (overall frequency 35.8%) and nodular toxic goitre (overall frequency 46.6%); and the highest frequency was in females with nodular toxic goitre (55.5%). Out of the total of 31 patients with prolapse, early systolic and holosystolic prolapse were each present in 12 patients, while mid-to-late systolic prolapse was found in 7 patients. Cross-sectional echocardiography demonstrated prolapse in 16 cases, the M-mode was positive in 5 cases while the two methods confirmed it in 10 patients. The prevalence of prolapse of the mitral valve in otherwise healthy Saudi subjects has previously been found to be 12-15%. This study has confirmed a high frequency of prolapse in hyperthyroid patients and has demonstrated that sex, ethnic or racial origin and type of hyperthyroidism are not determinants of this association.

Adolescent↗
PubMed1993

Gene expression in the developing cerebellum during perinatal hypo- and hyperthyroidism.

The intensity of p75NGFR receptor-like immunoreactivity and the mRNAs encoding p75NGFR, T alpha 1 alpha-tubulin, GAP-43 and the myelin proteins MBP and PLP were measured in the developing cerebellum to study the effects of perinatal thyroid hormone imbalance in rats. Results compared to age-matched controls provide in vivo evidence for differential gene regulation by thyroid hormone in the developing cerebellum. We found that p75NGFR immunoreactivity was strikingly elevated in hypothyroid rats, whereas p75NGFR mRNA content remained only twice as high as that of control levels on postnatal day 15 (P15). When p75NGFR immunoreactivity was still elevated in hypothyroid rats, Purkinje cells exhibited proximal axonal varicosities, axonal twisting and differences in axonal caliber. The mRNAs encoding proteins involved with neurite growth-promoting elements, T alpha 1 alpha-tubulin and GAP-43, were also increased in hypothyroidism, possibly reflecting a neuronal response to a deficiency in, or damage to, cerebellar neurons, or a general delay in their down regulation. Similar increases were not observed for the myelin specific genes. MBP and PLP mRNAs were first detected on P2 of hyperthyroid rats, and they increased with age. Hypo- or hyperthyroidism did not affect the initial onset of MBP and PLP expression, however, hyperthyroidism increased levels of PLP and MBP mRNAs between P2 and P10. By contrast, the most consistent decrease in MBP and PLP mRNAs in rats with thyroid hormone deficiency was observed only on P10. At later times (P15 and P30), the two mRNA levels were similar to controls in all groups. These results are consistent with a role for thyroid hormone in the earlier stages of cerebellar myelination. Hypothryoidism led to specific increases in T alpha 1 alpha-tubulin and GAP-43 mRNAs, and in the immunoreactivity and mRNA levels of p75NGFR receptor--all changes that may play a role in the observed abnormal neuronal outgrowth.

Animals↗