Beta-sympathetic blockade in hyperthyroidism

Hyperthyroidism, exophthalmos, and goiter: historical notes on the orbitopathy

BACKGROUND

Exophthalmos associated with goiter and/or symptoms of hyperthyroidism have been known since antiquity. It was not until around 1800 that a number of studies described this disorder in more detail.

SUMMARY

For many years the nature of the disease remained unclear and it was appreciated as either a cardiac or neurological disease. There was no agreement on treatment. Surgery on the thyroid, orbit, autonomous nerve system, and pituitary has been employed. Medical treatment was introduced around World War II. Later, as a consequence of the discovery of long-acting thyroid stimulator, it became apparent that Graves-Basedow's disease was an autoimmune disease and so was the exophthalmos, though many details of the pathophysiology remain in doubt.

CONCLUSIONS

This article presents a brief review of the history of the exophthalmos associated with thyroid disease.

Non-selective and selective beta-1-adrenoceptor blocking agents in the treatment of hyperthyroidism

Treatment for one month with propranolol or atenolol, a selective beta-1-adrenoceptor blocking agent, was evaluated in 20 hyperthyroid patients. The patients improved to the same extent on either drug, as shown by a clinical diagnostic index. Basal metabolic rate decreased by 11% during both treatments, while it was unchanged in seven untreated hyperthyroid controls. Thyroxine concentration did not change during any treatment. During propranolol treatment T3 decreased from 4.6 to 3.9 nmol/l, while no changes were observed during atenolol treatment or in the control group. No significant changes were seen in free T4, free T3 or rT3 concentrations on any treatment, although free T3 was observed to decrease slightly during propranolol treatment. Thus, the improvement of the clinical symptoms of hyperthyroidism cannot be explained by diminished thyroid hormone concentrations in serum, since the reduction was small during propranolol and absent during atenolol treatment.

Oxygen consumption in patients with hyperthyroidism before and after treatment with beta-blockade versus thyrostatic treatment: a prospective randomized study

OBJECTIVE

To evaluate randomly the effect of thyrostatic treatment (tiamazole) versus selective (metoprolol) and nonselective beta-blockade (propranolol) on whole-body energy metabolism in women with hyperthyroidism.

SUMMARY BACKGROUND DATA

beta-blockade is used as an alternative to thyrostatic drugs in the preoperative treatment of patients with hyperthyroidism. beta-blockers have well-established symptomatic effects, but in contrast to antithyroid drugs beta-blockade is thought to lack direct effects on the increased metabolism in hyperthyroidism.

METHODS

Whole-body oxygen consumption and carbon dioxide production was measured in a semiopen canopy system with paramagnetic O2 and infrared CO2 sensors. A constant flow generator and the gas-dilution method for calculation of gas flow were used. Anabolic parameters were body weight, triceps skinfold, and arm muscle circumference.

RESULTS

Tiamazole normalized oxygen consumption and induced signs of anabolism with improved nutritional state. Metroprolol did not affect oxygen consumption. Propranolol reduced elevated oxygen consumption by 54%. Body weight and other anthropometric assessments were stable after specific and nonspecific beta-blockade, which also led to symptomatic relief in approximately 90% of the patients.

CONCLUSION

Tiamazole was the most effective drug to oppose the adverse effects of hyperthyroidism. Therefore, thyrostatic agents are recommended for preoperative treatments of patients with severe catabolic hyperthyroidism. Whenever beta-blockers are chosen for treatment of hyperthyroidism, propranolol (beta 1 + beta 2) has an advantage because it reduces the metabolic rate, whereas selective beta 1-blockade seemed to provide only symptomatic relief, related to the normalization of heart rate.

The effect of propranolol, verapamil and dantrolene treatment on cardiac hypertrophy, enhanced myocardial contractility and tachycardia in the hyperthyroid rat

Experimentally induced hyperthyroidism is associated with cardiac hypertrophy, tachycardia and elevated myocardial contractility. To investigate the possibility of ameliorating the cardiac changes pharmacologically, hyperthyroid rats were treated with propranolol, verapamil or dantrolene. Cardiac hypertrophy was assessed from the heart mass: body mass ratio and cardiac function was measured in vitro. Both verapamil and propranolol reversed the cardiac hypertrophy of the hyperthyroid animals from 0.92 +/- 0.02 mg.g-1 to 0.70 +/- 0.01 mg.g-1 (P less than 0.001) and 0.72 +/- 0.02 mg.g-1 (P less than 0.001) respectively. Verapamil was effective in reducing the spontaneous heart rate from 331 +/- 8 beats.min-1 to 273 +/- 7 beats.min-1 (P less than 0.001) while propranolol reduced the dP/dtmax of the hyperthyroid hearts from 4089 +/- 87 mmHg.s-1 to 3497 +/- 97 mmHg.s-1 (P less than 0.001). Dantrolene had no effect on any parameter. We conclude from our results that cardiac hypertrophy of the hyperthyroid heart can be reversed by treatment with propranolol and verapamil probably via their inotropic and chronotropic properties.

Catabolic effects of thyroid hormone excess: the contribution of adrenergic activity to hypermetabolism and protein breakdown

Although patients with thyrotoxicosis improve clinically after treatment with beta-adrenergic blocking drugs, it has never been established whether the hypermetabolism and body protein wasting caused by thyroid hormone excess are actually mediated by adrenergic mechanisms. To evaluate this issue, we measured basal energy expenditure, epinephrine-stimulated calorigenesis, and leucine kinetics (an index of body protein catabolism) in six normal volunteers before and after triiodothyronine (T3) administration (150 micrograms/d for 1 week). Serum T3 rose nearly threefold (P less than 0.001) during T3 administration, producing significant increases in basal metabolic rate (21%, P less than 0.001), nitrogen excretion (45%, P less than 0.001), and leucine flux (45%, P less than 0.01). In response to epinephrine infusion, the absolute rise in metabolic rate above basal was 57% greater in the thyrotoxic condition (P less than 0.02). Although beta-adrenergic blockade with intravenous propranolol totally abolished the calorigenic response to epinephrine, it had no detectable effect on either the accelerated basal metabolic rate or the augmented body protein catabolism caused by thyroid horomone excess. Our data suggest that in the basal, resting state, the increased metabolic rate and accelerated protein breakdown caused by thyroid hormone are not adrenergically mediated. However, under nonbasal conditions (when sympathetic activity is stimulated), enhanced responsiveness to catecholamine calorigenesis may exaggerate the hypermetabolic state and thereby contribute to weight loss and other clinical manifestations of thyrotoxicosis. This mechanism may explain the clinical efficacy of beta-adrenergic blocking agents in the treatment of thyrotoxicosis.

Cardiac performance in thyrotoxicosis: analysis of 10 untreated patients

This study attempts to define cardiac performance at rest and during exercise in patients with untreated thyrotoxicosis. We studied 7 women and 3 men, aged 23 to 59 years (40 +/- 10, mean +/- standard deviation [SD]) and compared the results with those obtained in 12 normal subjects. In patients with thyrotoxicosis, the rhythm was sinus and the only untoward symptom was palpitations; the resting electrocardiographic results were normal in 8 patients and showed left ventricular hypertrophy in 2 patients; the left ventricular ejection fraction and volumes (measured by radionuclide ventriculography) were normal at rest. During exercise, 1 patient had dyspnea and 7 had leg fatigue; 2 were asymptomatic. Also, 7 patients had greater than or equal to 5% increase in left ventricular ejection fraction, 2 had no change, and 1 had a decrease. In all 10 patients, the exercise ejection fraction was greater than or equal to 60%. All normal subjects had a greater than or equal to 5% increase in ejection fraction during exercise. There were no significant differences at rest between patients with thyrotoxicosis and normal subjects in blood pressure, ejection fraction, end-diastolic volume, stroke volume, end-systolic volume, or cardiac output, but the heart rate was significantly higher in patients with thyrotoxicosis (91 +/- 10 versus 80 +/- 12 beats/min, p less than 0.05). During exercise, there were no significant differences between patients with thyrotoxicosis and normal subjects in blood pressure, end-diastolic volume, stroke volume, end-systolic volume, or cardiac output. The exercise ejection fraction was significantly lower in patients with thyrotoxicosis than in normal subjects (68 +/- 10% versus 75 +/- 4%, p less than 0.05). Cardiac performance is normal at rest in patients with thyrotoxicosis, but during exercise abnormal left ventricular reserve occurs in some patients.

Acute effect of atenolol on serum thyroid hormones in hyperthyroid patients

The effect of atenolol on serum thyroid hormones levels is controversial. To get more information on this problem we studied the effect of propranolol and atenolol on plasma thyroid hormone concentrations in 20 thyrotoxic patients. Propranolol but not atenolol caused a significant decrease in T3 levels whereas no significant changes wee observed in T4 levels after both propranolol and atenolol administration.

Sotalol in hyperthyroidism

Ten hyperthyroid patients were studied before and after 2 weeks' beta-adrenoceptor blockade with sotalol. The following variables were measured: resting pulse rate, blood pressure, weight, thyroid hormone levels, plasma lipids, alkaline phosphatase, plasma glucose and insulin responses to oral glucose, bromsulphthalein retention and the 24-h urinary excretion of calcium, hydroxyproline, creatine and creatinine. Sotalol produced a significant fall in pulse and blood pressure. Weight loss continued during treatment. No metabolic changes of any consequence were found. It is concluded that sotalol should not be used as the sole treatment of a patient with hyperthyroidism.

Pindolol-induced tremor

Five patients were treated with pindolol for various indications. The patients called attention to the appearance of fine tremors in their extremities 6-72 hr after starting treatment with the drug. The tremors disappeared 24-72 hr after stopping the drug. Beta-adrenoceptor-blockers are known to suppress different types of tremor and the paradoxical appearance of tremors during pindolol treatment is attributed to its powerful partial agonist activity. To the best of the authors' knowledge this side effect has not been previously described in the literature.

Plasma cyclic nucleotide responses to insulin-induced hypoglycaemia and methacholine in patients with hyperthyroidism

The effect of insulin-induced hypoglycaemia and methacholine on plasma cAMP and cGMP levels was studied in normal volunteers, hyperthyroid and hypothyroid patients. A significant positive correlation existed between the maximal increase in plasma cAMP and the maximal decrease in plasma glucose in normals during insulin-induced hypoglycaemia. Therefore, the plasma cAMP response is considered to be dependent on the degree of hypoglycaemia, rather than the dose of insulin. The cAMP response to hypoglycaemia was significantly higher in hyperthyroid patient, and was lower in patients with hypothyroidism than in normals. The cAMP response of the hyperthyroid patients was normalized when their hyperthyroidism was controlled after 3 months of treatment. The plasma level of cGMP was slightly elevated during hypoglycaemia, but there was no significant difference between controls and hyperthyroid patients. The cGMP response to methacholine, which is probably mediated by cholinergic receptors, was significantly potentiated in hyperthyroid patients. The cAMP response, which is presumably dependent on endogenous catecholamines secreted during methacholine-induced hypotension, was also enhanced in hyperthyroid patients. It is likely that beta-adrenergic receptor responses and cholinergic receptor responses are both enhanced in hyperthyroidism.

Propranolol, triiodothyronine, reverse triiodothyronine and thyroid disease

Propranolol alone was given to sixteen hyperthyroid, and concomitantly with thyroxine therapy to ten hypothyroid patients. Following treatment of the hyperthyroid group for 1-2 weeks there was a significant decrease in serum triiodothyronine (T3) which correlated with the plasma propranolol steady state concentration. The serum reverse T3 (rT3) rose significantly. Weight loss ceased in this group while weight gain occurred in patients who had a marked fall in serum T3. One patient with T3 toxicosis went into remission. The reduction in serum T3 was maintained in six patients receiving propranolol for more than 1 month. In the hypothyroid group the mean serum T3 level achieved with 0.15 mg thyroxine per day was significantly lower than in a control group who did not receive propranolol. In five patients following propranolol withdrawal there was a significant rise in T3, a fall in rT3 and TSH, and weight loss. Propranol may therefore have a clinically significant and direct action on the peripheral conversion of thyroxine to T3 and rT3.

Propranolol in thyrotoxicosis. Cardiovascular changes during thyroidectomy in patients pre-treated with propranolol

The cardiovascular changes during anaesthesia and thyroidectomy have been studied in seven thyrotoxic patients prepared with propranolol. The heart rate and cardiac rhythm remained very stable throughout surgery. A 20% increase in mean arterial pressure occurred during surgical stimulation. A decrease in cardiac output, due to decreased stroke volume, occurred during surgical stimulation. A decrease in cardiac output, due to decreased stroke volume, occurred during surgery, reaching a maximum of 21% during ligation of the thyroid vessels and returning to pre-operative values by the end of surgery. The fall in cardiac output was accompanied by raised central venous pressure and raised total peripheral resistance.

Haemodynamic effects of beta-adrenergic blockade in hyperthyroid patients with and without heart failure

Haemodynamic studies were performed in 10 patients with uncomplicated thyrotoxicosis and seven with thyrotoxic cardiac failure. The cardiac output of those with uncomplicated hyperthyroidism was higher than normal at rest. After 2 mg of intravenous propranolol there was a 13% fall but the level was still higher than normal. In patients with thyrotoxic cardiac failure the resting cardiac output was normal, but it fell after propranolol by 30% to subnormal levels. In both groups there was an increase in right heart pressures and fall in the rate of increase in arterial pressure, which indicated a decrease in myocardial contractility. These results indicate that increased autonomic activity is a compensatory phenomenon in hyperthyroid heart failure and that its abolition by beta-blocking drugs has a deleterious effect on cardiac function. They are therefore contraindicated in patients with thyrotoxic heart failure.

A case of associated thyrotoxicosis and phaeochromocytoma. A diagnositc problem

A case of phaeochromocytoma and thyrotoxicosis occurring in the same patient is described, in which the similarity between the signs and symptoms produced by the two conditions delayed full diagnosis until post mortem. The mechanisms involved in the production of these signs and symptoms are discussed.

Assessment by continuous cardiac monitoring of minimum duration of preoperative propranolol treatment in thyrotoxic patients

The effect of the beta-blocker, propranolol (40 mg 6-hourly orally) has been studied on the tachycardia of six patients with untreated thyrotoxicosis. Heart rate was monitored continuously using a light portable ECG recorder which allowed the patients to undertake normal activities during the recording periods. The most marked reduction in heart rate was evident at 24 h after starting propranolol treatment. In three of the patients there was only a minor further fall in heart rate despite continued propranolol administration, but in the remaining patients the reduction in heart rate with each successive day of treatment was more marked. These results suggest that if propranolol were to be used alone in the preparation of patients before partial thyroidectomy for thyrotoxicosis, a dose of 40 mg 6-hourly for 3-4 days might be sufficient.

Experimental hyperthyroidism III: Contractile responses to propranolol of the intact heart and of the isolated ventricular myocardium

The effect of propranolol on cardiac mechanics and haemodynamics was examined on isolated papillary muscle as well as in situ in the closed thorax in euthyroid and hyperthyroid cats. Under propranolol there occurred on isolated papillary muscle significant decreases of muscle contraction, contraction velocity, isometric tension rise velocity and load and velocity values of simultaneously determined force-velocity relations. The 50% decrease of the values found was demonstrable at ca. 5--8 mu/ml for euthyroidal muscles, at 0.3--0.5 mug/ml for hyperthyroidal muscles. Contractility indices determined in situ (dp/dtmax, VCEmax, extrapolated Vmax) showed in hyperthyroidism at equal propranolol concentration a decrease about twice as great as in euthyroidism. The findings, showing a raised responsiveness of the ventricular myocardium in experimental hyperthyroidism to the negative inotropic effect of propranolol are discussed with regard to the therapeutic use of propranolol in hyperthyroidism.

Experimental hyperthyroidism I. Hemodynamics and contractility in situ

The influence of experimental hyperthyroidism (intraperitoneal injection of crystalline L-thyroxine 1 mg/kg/day, 8-18 days) on cardiac mechanics in contractility in situ were studied in 30 hyperthyroid cats and compared with an euthyroid control group (n equals 30). 1. In hyperthyroidism left ventricular weight was considerably increased. Hypertrophy in hyperthyroidism represents a special case of myocardial hypertrophy, associated with an increase of myocardial performance. 2. Heart rate, systolic pressure, cardiac index, external cardiac work and tension time index were increased by 60-180 per cent. 3. Indices of contractility (dp/dtmax, t-dp/dtmax, dp/dtmax/IP) as well as isovolumetric force velocity relationships and VCE-max and Vmax demonstrated a considerable increase of contractility. Maximum rate isovolumetric pressure fall was increased by 120 per cent. Experimental hyperthyroidism is characterized by hypercirculation associated with increases of pressure, volume and velocity factors. The results are discussed with regards to the effects of increased cardiac mechanics on myocardial energy balance.

Atrial fibrillation and hyperthyroidism: a new look at their relationship and therapy with lidoflazine

Various kinds of dysrhythmias are found in association with hyperthyroidism but especially atrial fibrillation. The causal relationship of chronic atrial fibrillation and the endocrine disorder is controversial, as is its therapeutic management. Six patients with this particular combination of disorders were treated with lidoflazine: a new anti-anginal drug with anti-arrhythmic activity. All six patients returned to sinus rhythm on lidoflazine treatment although still hyperthyroid and remained in sinus rhythm during the follow up period ranging from 5 to 14 months. This occurred independently of antithyroid treatment. Some evidence is put forward that dysrhythmias and most commonly chronic atrial fibrillation are triggered off by hyperthyroidism or other disorders but that they are maintained by permanent cardiac damage due to arteriosclerosis, hypertension, coronary heart disease or rheumatic valve disease.

Successful chemical cardioversions and maintenance of sinus rhythm can be obtained independent of the thyroid function. Our results confirm the anti-arrhythmic activity of lidoflazine.

The surgical management of thyrotoxicosis

Preparation of selected thyrotoxic patients for partial thyroidectomy can be safely and quickly achieved using propranolol, the duration of preoperative therapy and the number of out-patient attendances being reduced by over 50 per cent. No problems have been encountered during preparation or intra-operatively in patients pretreated with propranolol when compared with patients pretreated with conventional preparations. The commonest form of morbidity following destructive therapy for thyrotoxicosis is hypothyroidism. In surgically treated patients hypothyroidism can be defined within 1 year of operation. The factors influencing postoperative hypothyroidism are discussed.

The sick sinus syndrome. A study of 15 cases

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Comparison of propranolol and LB 46 (prinodolol) on hyperthyroid tachycardia

LB 46 (prinodolol) a β-adrenergic receptor blocking drug which is more potent than propranolol in euthyroid subjects, is less effective in inhibiting hyperthyroid tachycardia. This is probably due to its intrinsic sympathomimetic activity.

Adenyl cyclase and cyclic AMP. Biochemical links in the regulation of myocardial contractility

The actions of many hormones may be related to their capacity to increase adenyl cyclase activity in their target organs. The evidence indicating that catecholamines and glucagon augment myocardial contractility by enhancing the activity of myocardial adenyl cyclase is summarized. Furthermore, data are presented suggesting that the inotropic actions of epinephrine and glucagon ultimately may be due to an increase in sarcotubular calcium stores, an effect that appears to be related to activation of an adenyl cyclase pool localized in the sarcoplasmic reticulum. Other hormones that may alter contractility through actions on the adenyl cyclase-cyclic AMP system are thyroid hormone, histamine, prostaglandin, and acetylcholine. Chronic cardiac decompensation in both the experimental animal and in man diminishes the effectiveness of glucagon as an inotropic agent and interferes with the mechanisms by which glucagon acts to enhance the activity of myocardial adenyl cyclase, changes that may be causally interrelated. Although an understanding of the adenyl cyclase system would seem to be extremely important for an understanding of the basic mechanisms responsible for modulating the intensity of the contractile state of the heart, further investigations are necessary for complete validation of this hypothesis.

The effect of altered thyroid state on atrial intracellular potentials

1. A group of rabbits was made hypothyroid by thyroidectomy, and another group was injected daily with L-thyroxine. After an appropriate interval respective alterations in thyroid state were confirmed by measurement of heart weight and of plasma iodine, and the animals' atria were isolated for recording.2. Measurements were made of atrial contractions, conduction velocity, spontaneous heart rate and maximum driven frequency, and action potentials were recorded with intracellular micro-electrodes.3. The resting potential and action potential heights were not affected by differences of thyroid state.4. Atrial arrhythmias are common in hyperthyroidism, rare in myxoedema. The possibility that hypothyroidism might reduce the rate of rise of the action potential, as do anti-arrhythmic drugs, and hyperthyroidism increase it, was investigated. Although the rate of rise was slower in hypothyroid atria at some driving frequencies, this could not alone account for an anti-arrhythmic effect, because at frequencies near the spontaneous heart rate the rate of rise of the action potential was not reduced.5. The duration of the repolarization phase of the action potential was greatly prolonged in atria from thyroidectomized rabbits, and was shortened in hyperthyroid atria. These changes could account for a reduced probability of arrhythmias in hypothyroidism, and the converse in hyperthyroidism.

Relationship between quantitated precordial movement and left ventricular function

The relationship between external records of precordial movement and ventricular function has been studied in 61 patients with various cardiac disorders by comparing the records of the apical impulse to the left ventricular volume. A significant correlation between external recordings and the volume data was found in patients with normal or increased ventricular volumes: Patients with a normal record in systole usually had normal end-diastolic and left ventricular stroke volumes; those with a hyperdynamic record in systole usually had an appropriate increase in stroke volume for increased end-diastolic volume; and those with sustained records usually had an increased end-diastolic volume without an appropriate increase in stroke volume, indicating poor myocardial function. Patients with a pressure-loaded left ventricle usually had a sustained record, but this appeared to be related to factors other than volume.

These studies demonstrate that records of the apical impulse may provide useful information about left ventricular function.