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PubMed2001

Sympathovagal imbalance in hyperthyroidism.

We assessed sympathovagal balance in thyrotoxicosis. Fourteen patients with Graves' hyperthyroidism were studied before and after 7 days of treatment with propranolol (40 mg 3 times a day) and in the euthyroid state. Data were compared with those obtained in a group of age-, sex-, and weight-matched controls. Autonomic inputs to the heart were assessed by power spectral analysis of heart rate variability. Systemic exposure to sympathetic neurohormones was estimated on the basis of 24-h urinary catecholamine excretion. The spectral power in the high-frequency domain was considerably reduced in hyperthyroid patients, indicating diminished vagal inputs to the heart. Increased heart rate and mid-frequency/high-frequency power ratio in the presence of reduced total spectral power and increased urinary catecholamine excretion strongly suggest enhanced sympathetic inputs in thyrotoxicosis. All abnormal features of autonomic balance were completely restored to normal in the euthyroid state. beta-Adrenoceptor antagonism reduced heart rate in hyperthyroid patients but did not significantly affect heart rate variability or catecholamine excretion. This is in keeping with the concept of a joint disruption of sympathetic and vagal inputs to the heart underlying changes in heart rate variability. Thus thyrotoxicosis is characterized by profound sympathovagal imbalance, brought about by increased sympathetic activity in the presence of diminished vagal tone.

Adult↗

PubMed1978

Enhanced phosphorylation of myocardial sarcoplasmic reticulum in experimental hyperthyroidism.

Calcium transport by cardiac sarcoplasmic reticulum (SR) was compared in hyperthyroid (HT) and euthyroid (ET) rats. Both Ca2+ uptake (97 +/- 3.1 nmol/mg per min in HT vs. 63 +/- 2.9 nmol/mg per min in ET, P less than 0.01) and CA2+ -stimulated ATPase activity (61 +/- 4.1 vs. 37 +/- 1.6 nmol Pi/mg per min, P less than 0.01) were higher in the thyroxine-treated animals. These changes were accompanied by enhanced cyclic AMP-dependent phosphorylation of cardiac SR in hyperthyroid rats (180 +/- 4.3 pmol Pi/mg per min vs. 117 +/- 4.2 pmol Pi/mg per min, P less than 0.01). SDS-polyacrylamide gel electrophoresis of cardiac SR showed that phosphorylation of a 22,000-dalton protein (phospholamban) primarily accounted for the differences between the two groups. There was no difference in the rate of SR dephosphorylation by endogenous phosphoprotein phosphatase between HT and ET rats. Differences in cyclic AMP-dependent phosphorylation between the two groups were blunted in the presence of excess exogenous cyclic AMP-dependent protein kinase. These results suggest that increased levels or activity of endogenous cyclic AMP-dependent protein kinases may partially explain enhanced calcium transport by the cardiac SR of hyperthyroid animals.

Animals↗

PubMed1996

Noninvasive indexes of cardiac systolic and diastolic function in hyperthyroid and senescent mouse.

The mouse is a common model for transgenic manipulation, however, their small size has made hemodynamic study difficult. A noninvasive 10-MHz pulsed Doppler probe was used to measure aortic and mitral flow velocities in anesthetized, intact mice to study the effects of aging and hypethyroidism (induced by thyroxine) one systolic and diastolic cardiac function. In 10 hyperthyroid mice peak aortic velocity (PAV, an index of systolic function) was 34% higher than in 10 control mice (108 +/- 2 vs. 80 +/- 3 cm/s, P < 0.05). The ratio of early to late mitral filling velocity (E/A ratio, an index of diastolic function) was 47% higher (5.6 +/- 0.8 vs. 3.8 +/- 0.2, P < 0.05) in the hyperthyroid mice. In six old (30 mo) mice PAV was similar to eight young (4 mo) mice (73 +/- 3 vs. 75 +/- 3 cm/s), but the E/A ratio was 59% lower (1.8 +/- 0.3 vs. 4.4 +/- 0.4, P < 0.05). Despite a wide range of observed heart rates, the systolic and diastolic parameters of the groups were clearly separated. We conclude that cardiac systolic and diastolic function in mice, measured by pulsed Doppler ultrasound, are similar to larger species both in magnitude and in their response to hyperthyroidism and aging.

Aging↗

PubMed2006

Oxidation of myosin heavy chain and reduction in force production in hyperthyroid rat soleus.

We tested the hypothesis that a force reduction in hyperthyroid rat soleus muscle would be associated with oxidative modification in myosin heavy chain (MHC). Daily injection of thyroid hormone [3,5,3'-triiodo-L-thyronine (T3)] for 21 days depressed isometric forces of whole soleus muscle across a range of stimulus frequencies (P < 0.01). In fiber bundles, hyperthyroidism also led to pronounced reductions (P < 0.01) in both K+ - and 4-chloro-m-cresol-induced contracture forces. The degrees of the reductions were similar between these two contractures that were induced by distinct reagents. Treatment with T3 elicited a significant decrease ( approximately 14%; P < 0.05) in the relative content of MHC contained in myofibrillar proteins. The content of carbonyl groups in myofibrillar protein extracts was elevated (P < 0.05) by approximately 50% in T3-treated muscles. Immunoblot analyses on T3-treated muscles showed a greater increase (106%; P < 0.05) of the carbonyl content in MHC than in myofibrillar protein extracts. These data suggest that in hyperthyroidism the decrease in force production of skeletal muscles may stem primarily from failure in myofibrillar protein function resulting from oxidative modification of MHC.

Animals↗

PubMed2001

Early fractures and occult hyperthyroidism: McCune-Albright syndrome?

McCune-Albright syndrome (MAS) is a sporadic disease characterized by fibrous bone dysplasia, café-au-lait spots and hyperfunctional endocrinopathies. We report a 2.5-year-old child with MAS with an early and nonclassic onset. He was admitted to our attention for frequent fractures without clinical signs of endocrinopathies, found to have asymptomatic, nonautoimmune hyperthyroidism. The diagnosis of MAS was based on RX and MR imaging associated with hyperthyroidism. It is not clear if there was a correlation between the severity of bone disease and the presence of thyroid disorder. At the moment no standard treatment exists for bone fibrous dysplasia and hyperthyroidism in children before the age of 6 years.

Child, Preschool↗

PubMed2002

Ovarian ultrasound and ovarian and adrenal hormones before and after treatment for hyperthyroidism.

OBJECTIVE: To relate thyroid, steroid and pituitary hormones to ovarian ultrasonographic findings in hyperthyroid patients before and during treatment. STUDY DESIGN: Ultrasonography of the ovaries and serum hormone determination by immunoassay were performed before and during thiamazole therapy in 18 women of fertile age treated for hyperthyroidism at the Danderyd Hospital from 1996 to 1998. RESULTS: When hyperthyreotic, the patients had elevated serum levels of sex hormone-binding globulin (SHBG) and subnormal values of cortisol, free testosterone (fT) and dehydroepiandrosterone (DHEA). In the euthyreotic state following treatment, endocrine variables were normalized. Patients with a short duration of the disease had higher pretreatment levels of free thyroxine (fT4), SHBG and testosterone and lower corticosteroid binding globulin (CBG) and cortisol levels compared to patients with a long duration of the disease. The pretreatment ultrasonographic picture was abnormal in 16 of 18 patients. Of the 8 patients who were examined by ultrasonography after 3 months of treatment, all but 1 showed a normal picture. Samples from patients showing an abnormal ultrasonographic picture had significantly higher fT4 and lower free testosterone (fT) values than samples from patients with a normal ultrasonographic picture. CONCLUSION: Ultrasonographic findings showing a multicystic/multifollicular picture, resembling polycystic ovaries (PCO), in hyperthyroidism may be related to direct effects of thyroid hormones on the ovaries and/or altered intraovarian androgen environment due to elevated SHBG levels. It is highly recommended to assess the thyroid status in patients with multicystic/multifollicular ovaries/PCO.

Adrenal Cortex Hormones↗

PubMed1985

Hypercalcemic encephalopathy in the course of hyperthyroidism.

A hypercalcemic condition can be observed in association with hyperthyroidism. The case of a patient suffering from hypercalcemia and hyperthyroidism is reported. A confusional state and EEG alterations, among which diffuse monomorphic delta rhythms were remarkable, are shown. As soon as normalization of calcemia was achieved, a rapid clinical and EEG improvement took place. A hypothetical interpretation is proposed, according to which a prolonged, though inconstant, and mild hypercalcemia in the course of hyperthyroidism could determine an encephalopathy, concealing in some way thyrotoxic symptoms.

Brain Diseases↗

PubMed1993

Recurrent polyradiculoneuropathy with hyperthyroidism.

A 30-year-old woman, who had had two episodes of distal dominant sensorimotor disorders in the extremities, developed again sensorimotor involvement in the distal portion of all limbs. She was also found to have hyperhidrosis, tachycardia and goiter. Neurological and endocrinological examinations led to a diagnosis of coexistence of recurrent polyradiculoneuropathy and hyperthyroidism. Treatment with thiamazole resulted in improvement of the neurological features as well as of hyperthyroidism. The relationship between polyradiculoneuropathy and hyperthyroidism is discussed.

Adult↗

PubMed1986

Action of hypo- and hyperthyroidism on the postmortal decay of acetylcholine in the rat spinal cord.

The postmortal decay of acetylcholine (Ach) was studied in the cervical spinal cords of rats in conditions of hyper- and hypothyroidism. The modifications of thyroid function were achieved either by chronic (20-25 days) administration of l-thyroxine or of methimazole. The basal metabolic rate and plasma T4 concentration were measured to estimate the degree of modification of thyroid activity. The levels of Ach at the start of postmortal decay were evaluated by extrapolation to time 0 of the curves of the postmortal decay of Ach and the levels of Ach at stabilization were estimated from the means of all the measures made at lapses of time over 100-200 s from death. In low and high hypothyroidism a reduction (53 and 72%, respectively) of the levels of Ach was found. A similar effect was found in hyperthyroidism: a 73 and 63% reduction of Ach levels in high and low hyperthyroidism, respectively. The level of Ach at stabilization of the postmortal decay increased only in hyperthyroid rats. The process by which Ach is destroyed is not modified in hyper- or hypothyroidism.

Acetylcholine↗

PubMed1995

Endothelium-dependent and endothelium-independent vasodilation in hyperthyroid and hypothyroid rats.

The effects of hyper- and hypothyroidism on the vasorelaxing responses to acetylcholine (ACh), sodium nitroprusside (NP), and CaCl2 were investigated in aortic strips and isolated perfused kidneys. The renal vascular reactivity to ACh and NP was increased in hyperthyroid rats, whereas the concentration-response curve to ACh in hypothyroid rats was flattened. In the renal vasculature from hypothyroid rats, NP produced a dual response: vasoconstriction at low doses and vasodilation at medium to high doses. Aortic strips from hyperthyroid rats showed an increased response to ACh without significant differences between hypothyroid and control groups. Aortic strips from all three experimental groups showed a similar relaxing response to CaCl2. These results indicate that: (1) the raised arterial pressure of hyperthyroid rats is not associated with a reduced endothelium-dependent and calcium-induced vasodilation, and (2) the changes in responsiveness to vasodilators in resistance vessels from hyper- and hypothyroid rats may play a role in the increased and decreased peripheral vascular resistances, respectively, previously reported in such animals.

Animals↗

PubMed1989

Changes in myosin isozyme expression during cardiac hypertrophy in hyperthyroid rabbits.

The myosin isozyme distribution in the left ventricle and in the interventricular septum of rabbits was studied after 3, 7, 11, 14 and 21 days of L-thyroxine (500 micrograms/kg/day) administration. Histochemical procedures were employed to identify V1 and V3 by their Ca2+ ATPase activity and their proportions were quantified through polyacrylamide gel electrophoresis. In the left ventricle, the subepicardium was the first to show the shift from V3 to V1, followed by the subendocardium. The intermediate region became heterogeneous by 11 days and remained so until 21 days. The right subendocardial and the intermediate regions of the interventricular septum were heterogeneous in the normal rabbit and hyperthyroidism resulted in a shift from V3 to V1 in both the right and left subendocardial regions of the septum. Like the left ventricle, the intermediate region of the interventricular septum remained heterogeneous. Localized accumulations of collagen were seen in all regions of the left ventricle and interventricular septum. From these results we conclude that in thyrotoxic myocardial hypertrophy the isozymic shift from V3 to V1 is progressive, region-specific and is directly correlated with the period of hyperthyroidism in the first 2 weeks. Prolonged hyperthyroidism results in localized accumulation of collagen which does not exhibit any regional specificity.

Animals↗

PubMed1985

Hyperthyroidism in end-stage renal disease.

We report the 2nd patient to have hyperthyroidism while on maintenance hemodialysis. This case is instructive because the diagnosis of hyperthyroidism in uremic patients is difficult due to similar signs and symptoms. This case report describes, for the first time, the unique interaction between hemodialysis and thyrotoxic heart disease. Paroxysmal atrial fibrillation and severe hypotension interfered with all hemodialyses. Only the correction of the hyperthyroid state and withdrawal of all beta-blocking agents allowed resumption of normal hemodialysis. The delayed gastric emptying and hypercalcemia ultimately resolved with return to the euthyroid state and did not recur during 10 months of follow-up.

Atrial Fibrillation↗

PubMed1978

Influence of hyperthyroidism on the rate of ethanol metabolism in man.

The rate of ethanol metabolism was studied in 3 hyperthyroidism patients without therapy and in 2 after 1 week of treatment with propylthiouracil and reserpine. The rate of ethanol metabolism (mg/kg/h +/- SEM) was 386 +/- 57 in the 3 hyperthyroid patients, 184.5 +/- 2.5 in the 2 treated patients and 159 +/- 15 in 12 euthyroid non-alcoholic subjects. The results suggest that hyperthyroidism markedly increases ethanol metabolism.

Adult↗

PubMed1985

Hodgkin's disease and hyperthyroidism.

In recent years we have had the occasion to observe hyperthyroidism in 6 patients with Hodgkin's disease. All patients had received Mantlefield irradiation and were disease-free when hyperthyroidism appeared. Hyperthyroidism allows three different pictures to be distinguished: 1 case report of Graves' disease without ophthalmopathy, 1 case report of Hashimoto's thyroiditis corresponding to a particular form called hashitoxicosis, and 4 case reports of atypical silent thyroiditis. Reports concerning case studies of postirradiation Graves' disease or Hashimoto's thyroiditis during Hodgkin's disease are only to be found exceptionally. Atypical silent thyroiditis was recently individualized, but no postirradiation case studies have been reported. It is suggested that these 6 cases represent a radiation-induced immune thyroid disease: physiopathology and predisposing factors are discussed.

Adult↗

PubMed1980

Tyrosine hydroxylase activity and catecholamine content in the adrenals of young hypo- and hyperthyroid rats.

The weight, the tyrosine hydroxylase (TH) activity and the catecholamine (noradrenaline and adrenaline) content of young rat adrenals have been measured from birth to 20 days after birth in relation to hypo- and hyperthyroidism. Hypothyroidism impairs the adrenal growth, while hyperthyroidism has no effect on the adrenal weight. Hypothyroidism is associated with an enhancement of TH activity and catecholamine content. In hyperthyroid rats, the increase in TH activity and catecholamine content is slower than in controls. In adult animals, TH activity and catecholamine content are less affected by thyroid function.

Adrenal Glands↗

PubMed1995

Subcorneal pustular dermatosis in a patient with hyperthyroidism.

A case of subcorneal pustular dermatosis (SPD) is reported in a 48-year-old man with a 2-year history of hyperthyroidism (Graves' disease). SPD has been reported in association with IgA monoclonal gammopathy, but to our knowledge it has not been associated with hyperthyroidism. The coexistence of hyperthyroidism and SPD suggests that immunologic factors may play a role in the pathogenesis of SPD.

Biopsy↗

PubMedDate not supplied

Follicular carcinoma of the thyroid with hyperthyroidism. A case report.

BACKGROUND: Follicular carcinoma of the thyroid in association with hyperthyroidism is rare. The malignant lesion may remain occult for a long time. Certain clinical and cytologic features may be helpful in raising the alarm. CASE: An elderly male with a history of occupational exposure to X rays, long-standing toxic multinodular goiter and clinical hyperthyroidism presented with a rapidly enlarging mass in the neck. Cytologic smears showed a prominent microfollicular pattern, scanty colloid, anisonucleosis and nuclear overlapping. The noteworthy feature was the presence of marginal vacuoles. The cytologic diagnosis of follicular neoplasm with highly suggestive malignancy was made. Subsequently, multiple pulmonary nodules provided radiologic evidence of possible metastatic spread. CONCLUSION: This case report demonstrates the rare association of follicular carcinoma of the thyroid with hyperthyroidism and analyzes certain high-risk clinical and cytologic features to be considered in the follow-up of long-standing hyperfunctioning multinodular goiter.

Adenocarcinoma, Follicular↗

PubMedDate not supplied

Aortic intimal thickening and myosin isoform expression in hyperthyroid rabbits.

The potential effect of thyroid hormones on the expression of cytoskeletal and cytocontractile proteins of vascular smooth muscle cells (SMCs) was examined by a panel of monoclonal antibodies and immunocytochemical procedures. L-Thyroxine was administered to adult New Zealand White rabbits for as long as 26 days, and the aortic SMC composition was studied at days 1, 2, 7, 15, and 26 from the beginning of hormonal treatment. A diffuse intimal thickening of the aorta became visible after 7 days of thyroxine administration. Histological and histochemical examination of intimal tissues from hyperthyroid rabbits revealed the presence of a homogeneous Sudan black-negative cell population. In immunofluorescence tests the intimal cells were found to be negative for antibodies specific for monocyte/macrophage or desmin and homogenously reactive (positive) for antibodies to vimentin and smooth muscle (SM) alpha-actin, thus indicating that cells present in the thickened intima were of the SM type. In addition, intimal SMCs from aortas of hyperthyroid rabbits showed a myosin isoform content similar to that found in normal developing aortic SM and in a specific medial SMC subpopulation of aortas from adult euthyroid animals. In the media underlying the intimal thickening, almost all the SMCs switched their myosin isoform expression toward the "immature" phenotype after 2 days of thyroxine treatment. When the level of thyroid hormones was reduced by propylthiouracil treatment, the medial SMC subpopulation with the immature myosin isoform content present in euthyroid rabbits completely disappeared. The study of DNA synthesis-related bromodeoxyuridine incorporation in aortas from hyperthyroid rabbits showed the presence of labeled nuclei in medial SMCs before the appearance of the intimal thickening as well as in the thickened intima and in the underlying media at days 7 and 15. These results are consistent with a specific role for thyroid hormones in inducing proliferation/migration of medial SMCs into the intima. Moreover, the switch in the expression of myosin isoforms induced by thyroid hormones appears to precede the accumulation of medial SMCs in the intima.

Actins↗