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PubMed1984

Radioactive iodine therapy in cats with hyperthyroidism.

Eleven cats with hyperthyroidism were treated with radioactive iodine (131I). Previous unsuccessful treatments for hyperthyroidism included hemithyroidectomy (2 cats) and an antithyroid drug (7 cats). Two cats had no prior treatment. Thyroid scans, using technetium 99m, showed enlargement and increased radionuclide accumulation in 1 thyroid lobe in 5 cats and in both lobes in 6 cats. Serum thyroxine concentrations were high and ranged from 4.7 to 18 micrograms/dl. Radioactive iodine tracer studies were used to determine peak radioactive iodine uptake (RAIU) and effective and biological half-lives. Activity of 131I administered was calculated from peak RAIU, effective half-life, and estimated thyroid gland weight. Activity of 131I administered ranged from 1.0 to 5.9 mCi. The treatment goal was to deliver 20,000 rad to hyperactive thyroid tissue. However, retrospective calculations based on peak RAIU and effective half-life obtained during the treatment period showed that radiation doses actually ranged from 7,100 to 64,900 rad. Complete ablation of the hyperfunctioning thyroid tissue and a return to euthyroidism were seen in 7 cats. Partial responses were seen in 2 cats, and 2 cats became hypothyroid. It was concluded that 131I ablation of thyroid tumors was a reasonable alternative in the treatment of hyperthyroidism in cats. The optimal method of dosimetry remains to be determined.

Animals↗
PubMedDate not supplied

[Somatotropin-synthesizing activity of the in vitro cultured adenohypophyses of intact, hypo- and hyperthyroid rats].

Somatotropin-synthetizing activity of the adenohypophyses cultivated in vitro in eu-, hupo- and hyperthyroid rats was investigated. The most pronounced persistence of the activity (89%) within 12 days is seen in the adenohypophyses of hypothyroid rats and less evident (41%) in the adenohypophyses of hyperthyroid animals in comparison with that of euthyroid rats (66%). The activity rise in the adenohypophyses of euthyroid hypothyroid rats is observed by the 6th day of cultivation, being more pronounced in the adenohypophyses of hypo- than euthyroid animals. The adenohypophyses cultivated in vitro in hypo- and hyperthyroid rats may serve as models for studying the adenohypophyseal somatotropic function disorders in hypo- and hyperthyroses.

Animals↗
PubMed1984

[Amiodarone and hyperthyroidism].

22 cases of hyperthyroidism occurring during or following treatment with amiodarone are reported and compared with more than 15 cases in the literature. The specific clinical features of these cases of hyperthyroidism are presented and the problems in interpretation of the laboratory thyroid function tests are discussed. A study of the course of these cases reveals a number of prognostic factors. Finally, the authors describe the practical management of this form of hyperthyroidism.

Adult↗
PubMed1980

[Effect of the dopamin antagonist metoclopramide on the TSH response after oral TRH in the TSH suppression syndrome ("preclinical hyperthyroidism"). Preliminary report].

The TSH response to exogenous TRH may be diminished or absent not only on overt hyperthyroidism but also in other situations, e.g. obesity, old age, multinodular goiter and depression. To elucidate the possible role of dopaminergic control of the TSH response to TRH in such patients, the oral TRH test (40 mg) was performed with and without simultaneous administration of metoclopramide (10 mg i.v.) in 20 patients known to have diminished or absent response to oral TRH (delta TSH < 1.0 mU/l). All patients had euthyroid basal levels of FT4-index and T3, and may thus be assumed to have "preclinical hyperthyroidism" (TSH suppression syndrome). In 11 patients the history suggested they were free of symptoms of mental depression, while 9 patients were considered by two independent examiners to have various degrees of depression. The TSH response to TRH in depressive patients was significantly increased when the dopamine-receptor-blocker metoclopramide (MCL) wad added. The delta TSH rose from 0.6 +/- 0.3 mU/l (SEM) without MCL to 8.8 +/- 1.8 mU/l with MCL (p < 0.002). In contrast, MCL failed to enhance the TSH response in non-depressive patients: the delta TSH was 0.7 +/- 0.3 mU/l without MCL, and with MCL 2.1 +/- 0.9 mU/l (n.s.). Thus the dopaminergic system appears to play a major role in modulating the sensitivity of the pituitary to TRH stimulation. In clinically doubtful situations, the combined metoclopramide-TRH test may be used to distinguish patients with a diminished or absent TSH response as a consequence of depression (central dopaminergic suppression) from patients with "preclinical hyperthyroidism" where the TSH response is suppressed by feedback control of TSH by thyroid hormones (thyroid autonomy).

Adult↗
PubMed1982

[In vitro and in vivo diagnosis of borderline hyperthyroidism].

The evaluation of "preclinical hyperthyroidism" includes laboratory and in vivo tests. The measurements of circulating total thyroxine (T4) and total triiodothyronine (T3) depend on the plasma concentration of thyroid hormone binding proteins. A simple approach, the calculation of the free T3 index (FT3I) and the augmented FT3I (aFT3I) from total T3 and T3-resin uptake corrects the total serum T3 for variation in thyroid hormone binding capacity. In a group of 95 patients with border-line elevated T3 levels we have correlated the results of FT3I and aFT3I with clinical, biochemical and radioisotope findings. It was shown that in patients with moderate elevation of T3 the FT3I and aFT3I are capable of distinguishing clearly between the euthyroid and hyperthyroid range. To detect an imbalance in the hypothalamic-pituitary-thyroid axis either the T4-suppression test or the TRH-test could be used. In 60 patients with "preclinical hyperthyroidism" we have compared both of them. In 77% of the patients the T4-suppression test and i.v. TRH-test provided concomitant results. In 13 patients without response to the i.v. TRH-test 7 showed a definite (more than 50%) and 6 a partial suppression (10-40%) of radioiodine uptake. This suggests that there is no sharp distinction between hyper- and euthyroidism.

Female↗
PubMed1983

Exogenous hyperthyroidism with osteoporosis.

Symptomatic osteopenia accompanied by subclinical hyperthyroidism developed in three women who were receiving excess thyroid hormone medication. Excessive thyroid replacement therapy resulted in mild hypercalcemia, hyperphosphatemia, and hyperphosphatasemia associated with diffuse skeletal demineralization and multiple fractures. Nondecalcified sections of double tetracycline-labeled iliac crest bone showed an accelerated rate of bone turnover with marked osteoclastosis and resorption of the cortical as well as the trabecular bone, typical of endogenous hyperthyroidism. Since thyroid hormones are among the most frequently prescribed medications, bone loss caused by exogenous hyperthyroidism may be more common than previously recognized.

Aged↗
PubMed1983

Changes in myocardial cell size and number during the development and reversal of hyperthyroidism in neonatal rats.

Increased workload was produced in newborn rats to study myocyte structure during conversion from hyperplastic to hypertrophic growth. Newborn rats were given L-thyroxine (T4) for 12 days and killed at that time or 20 days after discontinuing T4 treatment. Myocytes were isolated by a perfusion technique with collagenase. Cellular dimensions were determined with a sonic digitizer. Mean cell volumes were also determined with a Coulter counter for comparison with values obtained with the digitizer. Heart weight to body weight ratios were increased 30% in 12-day-old hyperthyroid rats. Cell length increased 22%, and cell volume increased 31% after 12 days of treatment with T4. The calculated number of ventricular myocytes indicated that T4 inhibited rather than stimulated hyperplastic myocyte growth. Twenty days after discontinuing T4 treatment, heart weight to body weight ratio and mean cell volume of treated animals were similar to control values. Cell length, however, remained significantly increased (14%), and cell width was significantly reduced (8%) after reversal of hyperthyroidism. We conclude that excess T4 inhibits hyperplastic myocyte growth in neonatal rats while stimulating hypertrophy of existing myocytes primarily by increasing cell length. Myocytes remained significantly longer after reversal of hyperthyroidism, indicating that structural changes may persist.

Animals↗
PubMed1983

[Chronobiological study of free thyroid hormones in hypothyroid and hyperthyroid subjects].

Previous reports demonstrate a circadian rhythm of the free thyroid hormones in healthy subjects. In this study we evaluated circadian variation of FT3 and FT4 in hyperthyroid and hypothyroid states. We considered six hyperthyroid patients, six hypothyroid patients and six control subjects. Blood samples were taken two hours apart from a catherterized arm vein. Data were evaluated by Halberg's cosinor analysis. The results show that FT3 and FT4 exhibit a circadian rhythm in healthy subjects, not evident in hyperthyroid and hypothyroid patients.

Adult↗
PubMed1983

Influence of nonthyroidal illnesses on serum thyroid hormone indices in hyperthyroidism.

Severe intercurrent nonthyroidal illnesses (diabetic ketoacidosis, myocardial infarction, fulminant hepatitis and bacterial pneumonia) in four thyrotoxic patients were associated with depression of total serum thyroxine (T(4)) and triiodothyronine (T(3)) values into the normal or even subnormal range. A diagnosis of hyperthyroidism was established by a combination of elevated radioactive iodine uptake, absent thyroid-stimulating hormone response to thyrotropin-releasing hormone or an elevated free T(4) by dialysis values. In the two of four cases that had a fatal outcome, there was a progressive decline in total T(4) and total T(3) values. In contrast, the two surviving patients had a progressive increase of total T(3) and total T(4) values into the hyperthyroid range as their underlying illness resolved. As has been seen with severe nonthyroidal illnesses, pronounced depression of total T(3) and total T(4) levels in hyperthyroid patients may also portend a poor prognosis.

Adult↗
PubMed1983

[Factitious hyperthyroidism caused by L-thyroxin abuse. Case report].

A 43 years old female was treated for 8 months with antithyroid drugs because of a difficult adjustable hyperthyroidism. In spite of this massive antithyroid therapy a threatening deterioration of the clinical picture occurred. The reason for it was the secret intermittent intake of up to 1200 micrograms lT4 daily motivated by private problems. The difficulties of a differential diagnosis between a thyrotoxicosis factitia and an endogenous hyperthyroidism is stressed. One should always consider a thyrotoxicosis factitia in the case of suggestion of a psychopathia and when thyroid hormone medication is used for suppressive thyroid hormone therapy or as a prophylaxis of goiter recurrence. In addition overweight, major personality disorders and resistance to antithyroid drugs are indicative for thyroid hormone abuse. Important indicators for the differentiation between a thyroid hormone abuse and an endogenous hyperthyroidism are a lack of technetium- or radioiodine-uptake in the thyroid and suppressed levels of thyroglobulin.

Female↗
PubMed1982

Serum gastrin and motilin in treated and untreated hyperthyroidism.

To study the gastrointestinal hormones in hyperthyroidism and the interrelations with the thyroid hormones, the preprandial serum gastrin and motilin were measured by radioimmunoassay in 104 patients before and after the treatments. The following results were obtained: 1) Serum gastrin concentration in hyperthyroidism was significantly higher than that of the control, and when the patients reached euthyroidism or hypothyroidism after the treatments, the gastrin concentrations in the serum decreased to the normal level. There was a positive correlation between the thyroid hormones and the serum gastrin. 2) Serum motilin concentration in hyperthyroidism was slightly lower than that of the control. As the patients reached the euthyroid or hypothyroid state after the treatments, an increasing tendency of motilin was observed, though the change was not significant. There was a slightly negative correlation in gastrin versus motilin and also in T4 versus motilin.

Adult↗
PubMed1982

[Activation of lipid peroxidation in liver mitochondria of rabbits with hyperthyroidism].

Lipid peroxidation (LPO) in liver mitochondria of normal and hyperthyroid rabbits was studied by recording chemiluminescence of mitochondrial suspensions, induced by Fe2+. It was shown that in mitochondria of the hyperthyroid animals, there takes place an increase in the "slow flash" amplitude of chemiluminescence and reduction in the latent period of the luminescence development, as compared to the similar phenomena in normal animals. Characteristic changes were also seen upon recording chemiluminescence of suspensions of the lipids isolated from mitochondria of normal and hyperthyroid animals. These data attest to LPO activation in liver mitochondria during hyperthyrosis. LPO activation is not the result of a direct action of thyroxine on the mitochondria, since the addition of the hormones to organelles in different concentrations (3.25 x 10(-8)- 1.6 x 10(-7) mol/mg protein) did not alter the chemiluminescence parameters. It is suggested that LPO activation seen in liver mitochondria during hyperthyrosis is determined by an increase in the unsaturated index of fatty acids of mitochondrial lipids.

Animals↗
PubMed1982

[Hyperthyroidism and the transmembrane potential of rat liver mitochondria].

Transmembrane potential of liver mitochondria in hyperthyroid rats was higher than that in euthyroid animals. Besides, a lower resistance to Ca2+ of the system responsible for the maintenance of the transmembrane potential was observed in the preparations from hyperthyroid rats. This was manifested in a decrease of the calcium dose required for the decay of the transmembrane potential and in a shorter period of Ca2+ retention by mitochondria. The observed decrease in the resistance to Ca2+ ions of the potential-maintaining system in hyperthyroid mitochondria is supposed to be determined by the increased activity of mitochondrial endogenous phospholipase.

Animals↗
PubMed1981

Cholesterol metabolism in hypothyroidism and hyperthyroidism in man.

Studies were carried out on cholesterol metabolism in 11 nonobese patients and 16 obese patients with hypothyroidism and 13 with hyperthyroidism. The patients underwent several investigations under metabolic ward conditions. Hypothyroid patients usually had an increase in low density lipoprotein (LDL)-cholesterol. Several mechanisms may have combined to cause a high LDL. For instance, the obese hypothyroid patients had an increase in cholesterol synthesis. Absorption of cholesterol also was increased frequently. However, other mechanisms not explored in this study probably contributed to most of the fall in LDL-cholesterol. Treatment of hypothyroid patients produced the expected fall in LDL. One possible mechanism could be that thyroid hormones enhance the conversion of cholesterol into bile acids; this mechanism has been suggested by other workers from animal studies. However, no evidence was obtained in either hypothyroid or hyperthyroid patients that thyroid hormones alter synthesis of bile acids. On the other hand, the hormones appeared to increase the synthesis of cholesterol. Patients with hypothyroidism frequently had supersaturated bile. The cause was mostly an enhanced secretion of biliary cholesterol associated with a tendency to obesity and increased synthesis of cholesterol. In contrast, the usually thin hyperthyroid patients did not have supersaturated bile. The studies show that thyroid hormones a) influence LDL-cholesterol by an action on the catabolism of LDL-independent of alterations in synthesis, catabolism, absorption, or excretion: b) stimulate synthesis of cholesterol; and c) affect biliary lipid metabolism in large part by influencing energy balance and cholesterol synthesis.

Adult↗
PubMed1980

Serum high-density lipoprotein cholesterol concentrations in hypo- and hyperthyroidism.

We studied alterations in the concentration of high-density lipoprotein cholesterol and of other lipid categories (total cholesterol, low-density lipoprotein cholesterol, very-low-density lipoprotein cholesterol, and triglycerides) in serum in hypo- and hyperthyroid states, and compared these findings with those of a control group. In the latter group the lipids showed an age-related increase in concentration but with a decrease in the eighth decade in all categories. In untreated hypo- and hyperthyroid subjects, all of the lipid values differed significantly from those of the controls but promptly returned to normal values upon treatment. In hypothyroid patients who are prone to develop coronary heart disease, the concentrations of high-density lipoprotein cholesterol were high, suggesting protection against heart disease, while the ratio to total cholesterol indicated the contrary. The exact opposite of these relationships was seen in hyperthyroid disorders. This apparent paradox suggests that the low-density lipoprotein cholesterol in serum, with its established atherogenic effect, should be given at least equal, if not more, weight than the concentration of high-density lipoprotein cholesterol in serum, with its alleged protective effect.

Adult↗
PubMedDate not supplied

Systolic time intervals in hyperthyroidism.

PEPI (pre-ejection period index), QS2I (total electromechanical systolic index), LVETI (left ventricular ejection time index), and PEP/LVET ratio were measured in 35 thyrotoxic patients. None of the patients had clinical evidence of heart disease nor received drugs which might have affected the systolic time intervals. the hyperthyroid subjects showed significant shortening of PEPI and significant reduction of PEP/LVET, which returned within normal limits when the patients became euthyroid during treatment. No correlation could be found between T3, T4, FTI and PEPI or PEP/LVET. However, serial measurements indicated that the fall toward the normal range of PEPI parallelled that of T3; the latter is considered the most important index of thyroid function. Our study suggests that PEPI and PEP/LVET ratio may be of great usefulness in detecting hemodynamic alterations in subjects with uncomplicated hyperthyroidism. Moreover, these methods may facilitate the diagnosis in unusual types of hyperthyroidism occurring in the absence of clinical signs of toxicosis. In addition, PEPI and PEP/LVET appear to be useful in detecting T3 toxicosis. Finally, serial controls of PEPI could represent a useful index to monitor the response to therapy.

Adolescent↗
PubMed1980

Single daily dose methimazole treatment of hyperthyroidism.

The effectiveness of methimazole used in a single daily dose was studied in 47 patients during their initial episode of hyperthyroidism, and in an additional eight patients during a relapse of hyperthyroidism. All patients become euthyroid using this method. Mean time required to achieve a euthyroid state was 16.7+/-1.1 weeks in the former group, and 14.9+/-2.9 weeks in the latter. In one patient there was an initial response to single daily dose therapy, but subsequently split dosage was required for control. The single daily dose regimen of antithyroid drugs will control hyperthyroidism in most patients. We have found that propylthiouracil will achieve this more rapidly than methimazole.

Adolescent↗
PubMed1980

Atypical features of hyperthyroidism in blacks.

Hyperthyroidism is reportedly uncommon in the indigenous populations of Africa. The presenting symptoms volunteered, the symptoms elicited by direct questioning, and the results of physical examination were therefore prospectively compared in 60 Black and 56 White patients with thyrotoxicosis attending a single thyroid clinic. Fewer Blacks than Whites volunteered information about weight loss, while more Blacks complained only of the presence of a goitre. A 'change' diagnosis of hyperthyroidism was made more frequently in Blacks. Symptomatology elicited by direct questioning and findings on physical examination were generally similar in each group, except that Blacks presented more frequently with complicated disease (cardiac failure and overt myopathy) and infiltrative ophthalmopathy. The frequency with which hyperthyroidism presents 'atypically' in Black compared with White patients may reflect educational, socio-economic and Cultural differences in the Black and White populations, and may partly explain the infrequency with which this disease is diagnosed in Blacks.

Adult↗