Resistance to thyroid hormone due to mutations in the THRB gene impairs bone mass and affects calcium and phosphorus homeostasis.

CONTEXT: Resistance to thyroid hormone (RTH) is an inherited syndrome of reduced tissue responsiveness to thyroid hormone, which is usually due to mutations in the thyroid hormone receptor ß gene (THRB). Few studies have been conducted to investigate bone and mineral metabolism in RTH. OBJECTIVE: The objective of the study was to evaluate the clinical and biochemical parameters related to bone and mineral metabolism in RTH due to mutations in the THRB gene (RTHß). DESIGN AND PARTICIPANTS: We conducted a cross-sectional study on 14 patients with RTHß (RTHG), eight adults and six children, and 24 control subjects (CG). OUTCOMES: Serum measures included total calcium (TCa), inorganic phosphate (iP), alkaline phosphatase (AP), parathyroid hormone (PTH), 25-hydroxyvitamin D (25OHD), osteocalcin (OC), carboxyterminal telopeptide (CTX), and fibroblast growth factor 23 (FGF-23). We estimated the renal threshold phosphate concentration (TmPO4/GFR) and assessed bone mass using dual X-ray absorptiometry. RESULTS: Adults and children with RTH showed higher serum levels of TCa than controls (P=.029 and, P=.018 respectively). However, only children with RTH exhibited lower serum levels of iP than controls (P=.048). FGF-23 was higher in RTHß children (P=.04). RTHß adults had lower whole-body (P=.01) and lumbar spine (P=.01) bone mineral density than control subjects. The same pattern was observed when the results were expressed as Z-scores between groups, with a lower value in RTHG than in CG for the lumbar spine of adults (P=.03). No difference was observed between groups in PTH, 25OHD, AP, OC, and CTX. CONCLUSION: Biochemical abnormalities are seen in children with RTH (Low iP, high FGF23), while high calcium (with normal UCa) is seen in RTH subjects of all ages, and later on, in adult life, low BMD is seen. Considering that the TRα1 isoform is the predominant TR in the skeleton, we hypothesize that probably these patients may exhibit enhanced calcium flux from bone to circulation. Our data represent a challenge for new studies to unveil the control of calcium and phosphorus homeostasis and fracture risk in these patients.

Differential expression of immune-modulatory molecule HLA-E in non-neoplastic and neoplastic lesions of the thyroid.

Human leukocyte antigen (HLA)–E is a non-classical molecule of the histocompatibility complex that functions as one of the main ligands of the Natural Killer (NK) cell inhibitory receptor CD94/NKG2A and inhibits its potent cytotoxic activity. Due to the important role of NK cells in combating neoplasm, we hypothesized that the differential expression of HLA-E could favor the progression of heterogeneous thyroid tumors.Using an immunohistochemistry technique in 143 biopsies of thyroid tumors, including benign and malignant neoplasms and goiters, we evaluated the expression of HLA-E among various tumor types and its association with the clinicopathological factors of diseases. We verified high HLA-E expression in all types of neoplastic tumors, although no significant differences between the groups were found. Low expression was observed in 95 percent of the goiter samples, showing significant differences between neoplastic and non-neoplastic lesions. Furthermore, a significant result was found with regard to the tumor size, with high HLA-E expression being related to smaller tumors. Therefore, our data suggest that an increase in HLA-E may be associated with the establishment of thyroid neoplasms, with either benign or malignant features.

Neonatal screening for cystic fibrosis in São Paulo State, Brazil: a pilot study

Cystic fibrosis is one of the most common autosomal recessive hereditary diseases in the Caucasian population, with an incidence of 1:2000 to 1:3500 liveborns. More than 1000 mutations have been described with the most common being F508del. It has a prevalence of 23-55 percent within the Brazilian population. The lack of population-based studies evaluating the incidence of cystic fibrosis in São Paulo State, Brazil, and an analysis concerning the costs of implantation of a screening program motivated the present study. A total of 60,000 dried blood samples from Guthrie cards obtained from April 2005 to January 2006 for neonatal screening at 4 reference centers in São Paulo State were analyzed. The immunoreactive trypsinogen (IRT)/IRT protocol was used with the cut-off value being 70 ng/mL. A total of 532 children (0.9 percent) showed IRT >70 ng/mL and a 2nd sample was collected from 418 (80.3 percent) of these patients. Four affected children were detected at two centers, corresponding to an incidence of 1:8403. The average age at diagnosis was 69 days, and 3 of the children already showed severe symptoms of the disease. The rate of false-positive results was 95.2 percent and the positive predictive value for the test was 8 percent. The cost of detecting an affected subject was approximately US$8,000.00 when this cystic fibrosis program was added to an existing neonatal screening program. The present study clearly shows the difficulties involved in cystic fibrosis screening using the IRT/IRT protocol, particularly in a population with no long-term tradition of neonatal screening.

Neonatal screening for cystic fibrosis in São Paulo State, Brazil: a pilot study.

Cystic fibrosis is one of the most common autosomal recessive hereditary diseases in the Caucasian population, with an incidence of 1:2000 to 1:3500 liveborns. More than 1000 mutations have been described with the most common being F508del. It has a prevalence of 23-55% within the Brazilian population. The lack of population-based studies evaluating the incidence of cystic fibrosis in São Paulo State, Brazil, and an analysis concerning the costs of implantation of a screening program motivated the present study. A total of 60,000 dried blood samples from Guthrie cards obtained from April 2005 to January 2006 for neonatal screening at 4 reference centers in São Paulo State were analyzed. The immunoreactive trypsinogen (IRT)/IRT protocol was used with the cut-off value being 70 ng/mL. A total of 532 children (0.9%) showed IRT >70 ng/mL and a 2nd sample was collected from 418 (80.3%) of these patients. Four affected children were detected at two centers, corresponding to an incidence of 1:8403. The average age at diagnosis was 69 days, and 3 of the children already showed severe symptoms of the disease. The rate of false-positive results was 95.2% and the positive predictive value for the test was 8%. The cost of detecting an affected subject was approximately US$8,000.00 when this cystic fibrosis program was added to an existing neonatal screening program. The present study clearly shows the difficulties involved in cystic fibrosis screening using the IRT/IRT protocol, particularly in a population with no long-term tradition of neonatal screening.

How frequently should a patient taking amiodarone be screened for thyroid dysfunction?

Amiodarone-induced thyroid dysfunction (AITD) is a common complication of amiodarone therapy and its prevalence varies according to iodine intake, subclinical thyroid disorders and the definition of AITD. There is no consensus about the frequency of screening for this condition. We evaluated 121 patients on chronic regular intake of amiodarone (mean intake = 248.5 +/- 89 mg; duration of treatment = 5.3 +/- 3.9 years, range = 0.57-17 years) and with stable baseline cardiac condition. Those with no AITD were followed up for a median period of 3.2 years (range: 0.6-6.7) and the incidence rate of AITD, defined by clinical and laboratorial findings as proposed by international guidelines, was obtained (62.8 per 1000 patients/year). We applied the Cox proportional hazard model to adjust for potential confounding factors and used sensitivity analysis to identify the best screening time for follow-up. We detected thyroid dysfunction in 59 (48.7%) of the 121 patients, amiodarone-induced hypothyroidism in 50 (41.3%) and hyperthyroidism in 9 (7.5%). Compared with patients without AITD, there was no difference regarding dosage or duration of therapy, heart rhythm disorder or baseline cardiac condition. During the follow-up of the 62 patients without AITD at baseline evaluation, 11 developed AITD (interquartile range, IR: 62.8 (95%CI: 31.3-112.3) cases per 1000 patients/year), 9 of them with hypothyroidism - IR: 11.4 (95%CI: 1.38-41.2), and 2 hyperthyroidism - IR: 51.3 (95%CI: 23.4-97.5). Age, gender, dose, and duration of treatment were not significant after adjustment. During the first 6 months of follow-up the incidence rate for AITD was 39.3 (9.2-61.9) cases per 1000 patients/year. These data show that AITD is quite common, and support the need for screening at 6-month intervals, unless clinical follow-up dictates otherwise or further information regarding the prognosis of untreated subclinical AITD is available.

How frequently should a patient taking amiodarone be screened for thyroid dysfunction?

Amiodarone-induced thyroid dysfunction (AITD) is a common complication of amiodarone therapy and its prevalence varies according to iodine intake, subclinical thyroid disorders and the definition of AITD. There is no consensus about the frequency of screening for this condition. We evaluated 121 patients on chronic regular intake of amiodarone (mean intake = 248.5 ± 89 mg; duration of treatment = 5.3 ± 3.9 years, range = 0.57-17 years) and with stable baseline cardiac condition. Those with noAITD were followed up for a median period of 3.2 years (range: 0.6-6.7) and the incidence rate of AITD, defined by clinical and laboratorial findings as proposed by international guidelines, was obtained (62.8 per 1000 patients/year). We applied the Coxproportional hazard model to adjust for potential confounding factors and used sensitivity analysis to identify the best screening time for follow-up. We detected thyroid dysfunction in 59 (48.7%) of the 121 patients, amiodarone-induced hypothyroidism in50 (41.3%) and hyperthyroidism in 9 (7.5%). Compared with patients without AITD, there was no difference regarding dosage or duration of therapy, heart rhythm disorder or baseline cardiac condition. During the follow-up of the 62 patients without AITD at baseline evaluation, 11 developed AITD (interquartile range, IR: 62.8 (95%CI: 31.3-112.3) cases per 1000 patients/year), 9 of them with hypothyroidism - IR: 11.4 (95%CI: 1.38-41.2), and 2 hyperthyroidism - IR: 51.3 (95%CI: 23.4-97.5). Age, gender,dose, and duration of treatment were not significant after adjustment. During the first 6 months of follow-up the incidence rate for AITD was 39.3 (9.2-61.9) cases per 1000 patients/year. These data show that AITD is quite common, and support the need for screening at 6-month intervals, unless clinical follow-up dictates otherwise or further information regarding the prognosis of untreated subclinical AITD is available.

Galactosaemia in a Brazilian population: high incidence and cost-benefit analysis.

OBJECTIVES: To study the incidence of galactosaemia in the state of São Paulo and the benefit/cost (B/C) ratio of the introduction of neonatal screening for galactosaemia, comparing it with a selective approach. METHODS: An enzymatic-colorimetric assay was used for the screening of total galactose (TG) in a sample of 10% of the births in São Paulo in one year and positive cases were confirmed by the activity of galactose-1-phosphate uridyltransferase (GALT). Detected and referred cases were genotyped using enzyme restriction studies for Q188R, N314D and S135L mutations of the GALT gene. The economic analysis was determined by calculating the B/C ratio and by analysis of sensitivity as a function of the incidence of the disease detected and the variation of the interest rate in the economy. RESULTS: 59 953 newborns were screened for TG, with 3 cases of galactosaemia being identified (0.26% false positives), corresponding to a frequency of 1:19 984 liveborns (95% confidence interval: 1:7494 to 1:59 953). One classical case and one Duarte 2 variant referred to as a selective approach were confirmed. With an incidence of 1:19 984, the B/C ratio was 1.04 for the 11.75% interest rate in effect in Brazil, with values already decapitalized. With a maximum possible incidence of 1:7494, the B/C ratio was 2.79. DISCUSSION: There is an economic advantage in introducing neonatal screening for galactosaemia in the national neonatal screening programme. This advantage could increase with a reduction of the current interest rates in the economy.

Incidence of congenital toxoplasmosis estimated by neonatal screening: relevance of diagnostic confirmation in asymptomatic newborn infants.

Congenital toxoplasmosis is rarely identified by routine clinical examination. The aim of this study was to estimate the incidence of the disease in the region of Ribeirão Preto, south-eastern Brazil. A definitive diagnosis was made on the basis of the persistence of anti-Toxoplasma IgG antibodies beyond 1 year of age. Blood samples obtained from 15,162 neonates and adsorbed onto filter paper were tested for anti-Toxoplasma IgM antibodies. Fifteen samples gave positive results. A definitive diagnosis was confirmed in five of the 13 infants (38.5%) who completed follow-up. These five infants presented with serum IgM and/or IgA antibodies, and clinical abnormalities. Disease incidence was estimated to be 3.3/10,000 (95% CI 1.0-7.7), indicating the need for preventive measures. Neonatal screening is feasible, but screening tests with a better performance are required; positive screening results must be carefully confirmed.

Neutrophils from Brazilian patients with Graves' disease: some biochemical and functional aspects.

Graves' disease shows important systemic inflammatory complications and has been considered to be systemic autoimmune thyroid, skeletal muscle and connective tissue syndrome. Neutrophils participate in the pathophysiology of the two major immune and inflammatory manifestations of the disease, ophthalmopathy and myxedema, and may worsen the inflammatory picture. In this study we analysed some biochemical and functional aspects of neutrophils in Graves' disease patients to assess their participation in these processes. The results show that the complement and/or Fcgamma receptor-mediated oxygen radical production by neutrophils was increased when patient cells were compared with controls. However the percentage of cells expressing complement and IgG receptors and the per-cell fluorescence, were similar, indicating that the increased oxidative burst was not due to an abnormal expression of mediating receptors. The production of hydrogen peroxide was also increased in hyperthyroid patient neutrophils as compared to controls. Conversely, antioxidant defences (superoxide dismutase activity and reduced glutathione content) in neutrophils from patients were not significantly different from healthy controls. The liberation of potent oxidative compounds together with the absence of adequate quenching of them by antioxidant mechanisms could be responsible for greater tissue damage in inflammatory conditions, as is the case in ophthalmopathy and myxedema patients. Considering our results and those of other workers, we encourage and suggest an associated antioxidant therapy to complement the conventional anti-thyroid therapy, especially in obvious inflammatory cases and in individuals who smoke.

Molecular and biochemical screening for the diagnosis and management of medullary thyroid carcinoma in multiple endocrine neoplasia type 2A.

Patients with Multiple Endocrine Neoplasia (MEN) type 2A are at risk for early medullary thyroid carcinoma (MTC). We performed different screening tests for MTC--a recently reported biochemical screening test using omeprazole-induced calcitonin (CT) stimulation and DNA analysis--in fifteen members of two non-consanguineous Brazilian families with MEN 2A. RET proto-oncogene analysis was carried out by direct DNA sequencing of PCR-amplified products for exons 10 and 11. Family 1 showed a germline mutation (C634Y) in three individuals; a sister and a brother with symptomatic MTC; the former also presented with pheochromocytoma and hyperparathyroidism, and her son was a nine-year-old boy of previously unknown status. Family 2 showed the C634R mutation only in the index case, who presented with cutaneous lichen amyloidosis in addition to MTC, pheochromocytoma and hyperparathyroidism. Neither her parents nor her four brothers showed this genetic abnormality, suggesting a de novo RET proto-oncogene mutation in this patient. The controls and patients presented normal basal gastrin levels and a significant increase after omeprazole. Basal CT levels were elevated in patients with MTC and undetectable in control and asymptomatic family members. No subject showed any increase in CT levels after omeprazole treatment. In conclusion, the two most frequent RET proto-oncogene mutations in MEN 2A are present in Brazilian families. In addition, the specificity of basal and omeprazole-stimulated calcitonin is rather limited, and the efficacy of the omeprazole test still needs to be systematically examined. Therefore, RET proto-oncogene analysis must be the first choice for a screening procedure to identify gene carriers in MEN 2A family members and to permit early prophylactic treatment of MTC.

Association of the HLA-DRB1*0301 and HLA-DQA1*0501 alleles with Graves' disease in a population representing the gene contribution from several ethnic backgrounds.

Graves' disease (GD) is the most frequent cause of hyperthyroidism. Although the etiology is not completely elucidated, there are several lines of evidence suggesting multifactorial mechanisms. Genetic, constitutional, and environmental factors are involved in its pathogenesis. Major histocompatibility complex (MHC) class II alleles have been associated with GD in several populations of distinct ethnic backgrounds and there is increasing evidence supporting an association between GD and HLA-DR3 in Caucasian populations. The MHC class II alleles were evaluated in 75 Brazilian patients presenting with GD and in 166 control individuals from the same geographic area. HLA-DRB, DQB, and DQA alleles were identified using polymerase chain reaction (PCR)-amplified DNA hybridized with sequence-specific probes. The HLA-DRB1*0301 allele was significantly increased in patients (34/75, 45.3%) as compared with controls (37/166, 22.3%, p = 0.009), conferring a relative risk (RR) of 2.8 and an etiologic fraction (EF) of 0.287. The HLA-DQA1*0501 allele was also overrepresented in patients (48/71, 67.6%) in relation to controls (24/71, 33.8%; p = 0.004), conferring an RR of 3.74 and an EF of 0.351. The susceptibility conferred by HLA-DQA1*0501 was independent of the HLA-DRB1*0301 allele. On the other hand, the HLA-DQB1*0602 allele was significantly decreased in patients (6/75, 8.0%) in relation to controls (53/166, 31.9%, p = 0.0008), conferring an RR of 0.18 and a preventive fraction of 0.267. Although the Brazilian population comprises individuals of several ethnic backgrounds, these results corroborate the participation of the HLA-DRB1*0301 and HLA-DQA1*0501 alleles as susceptibility markers for GD, and emphasize the participation of the HLA-DQB1*0602 allele as conferring protection against the development of the disease.

Frequent loss of heterozygosity on chromosomes 3p and 17p without VHL or p53 mutations suggests involvement of unidentified tumor suppressor genes in follicular thyroid carcinoma.

Follicular thyroid carcinoma (FTC) exhibits frequent loss of heterozygosity (LOH) on chromosomes 10q and 3p, suggesting involvement of tumor suppressor genes. We screened 14 FTC (10 Hurthle cell carcinomas and 4 nonoxyphilic FTC), 14 papillary thyroid carcinomas, and 7 follicular adenomas for LOH on chromosome arms 1p, 3p, 3q, 10p, 10q, 11p, 11q, 13q, 17p, and 17q. LOH was more frequent in FTC than in follicular adenoma or papillary thyroid carcinoma. In FTC, rates of LOH on 3p (86%), 17p (72%), and 10q (57%) were higher than the average rate of LOH (33%; P < 0.05). Most frequently involved were 3p21-25 and 17p13.1-13.3, the sites for the VHL (3p25-26) and p53 (17p13.1) tumor suppressors. We, therefore, characterized these genes by dideoxy fingerprinting and DNA sequencing. Two FTC had mutations in p53, but only 1 of these exhibited LOH at 17p. No VHL gene mutations were found. Thus, neither p53 nor VHL genes play a significant role in the pathogenesis of differentiated thyroid cancer. LOH on 17p, but not on 3p or 10q, was correlated with mortality. Accordingly, 3p and 10q LOH may represent early, and 17p LOH late, events in FTC development. The data suggest the presence of novel tumor suppressor genes on chromosomes 3p and 17p that may be important in the pathogenesis of FTC.

[Excretion of 99m Tc-DISIDA through the bile ducts in the etiological diagnosis of neonatal cholestasis]. / Excreção de 99mTc-DISIDA pelo trato biliar no diagnóstico etiológico da colestase neonátal.

We evaluated 51 tests of 99mTc-DISIDA excretion by the biliary tree in patients with neonatal cholestasis. The aim of the present study was to verify the value of this test in the differentiation of this syndrome, correlating it to the clinical and laboratory data. The case studied were divided into two groups: extrahepatic biliary atresia, 26 patients (50.9%) and no-extrahepatic biliary atresia, 25 patients (49.1%). Analyzing the results, we concluded that this test had 96% sensitivity, 56% specificity, 69% positive predictive value, 93% negative predictive value and 76.5% accuracy. The accuracy of this test was only lower than that of hepatic biopsy. We conclude that the hepatobiliary scintigraphy was very useful in the definition of extrahepatic biliary atresia, with less value in the group of neonatal hepatitis, perhaps due to the delayed referral of the patients, short time of the scintigraphy study or factors related to the etiology of cholestasis itself.

Luteinizing hormone response to clomiphene citrate in central precocious puberty.

OBJECTIVE: The aim of the present study was to determine the LH response to clomiphene citrate administration in children with central precocious puberty and different bone ages to gain insight into the hypothalamic maturation mechanism. PATIENTS AND METHODS: Twelve children with untreated central precocious puberty were studied. Five had central nervous system lesions and seven had idiopathic central precocious puberty. Their chronological and bone ages ranged from 1.7 to 8.8 years and 3.5 to 13.5 years, respectively. Clomiphene citrate (3 mg/kg/day) was administered orally for 7 days. Blood samples were collected on days 0, 6 and 8. LH and FSH were determined by RIA. The results were compared with GnRH responses or with bone age. RESULTS: No increase over basal LH levels was detected in four patients, but increased LH levels were detected in the remaining eight during clomiphene administration. The shift from negative to positive responses was around 8-9 years bone age. The sum of LH responses (days 6 and 8) to clomiphene citrate, and particularly the 8th-day LH levels, were significantly correlated with their respective bone age (r = 0.83). However, the LH responses to GnRH were not significantly correlated with bone age or with LH responses to clomiphene. CONCLUSIONS: This study shows that the LH responsiveness to clomiphene citrate in central precocious puberty increases with skeletal maturation, indicating that the activation of the hypothalamic pubertal mechanism in central precocious puberty may progress in a gradual sequence. These changes in LH response to clomiphene in central precocious puberty mimic those observed with the development of normal puberty, but occur at a much earlier age.

Age-induced decreases in the messenger RNA coding for the sarcoplasmic reticulum Ca2(+)-ATPase of the rat heart.

Age-associated slowing of cardiac relaxation related to the decline in the Ca2+ pump function of cardiac sarcoplasmic reticulum (SR) has been previously described. It is unclear if the decreased Ca2+ pump function results from a lower amount of Ca2(+)-ATPase protein or a decreased pumping activity of the enzyme. To determine if these alterations could be mediated by changes in the amount of the protein itself, the level of the messenger RNA (mRNA) coding for the Ca2(+)-ATPase of the SR of Fischer rat hearts (4- and 30-month-old rats) were quantitated with a Northern blotting technique. We observed that the levels of SR Ca2(+)-ATPase mRNA were 60% lower in old rats as compared with young rats, suggesting that a quantitative reduction in the levels of the corresponding protein could occur during aging to explain the delayed diastolic relaxation documented in old animals as opposed to a change in the specific activity of this enzyme. The thyroid hormone responsiveness of SR Ca2(+)-ATPase mRNA has been previously established. We have found in this study that the thyroxine levels were consistently lower in old rats; however, this difference was relatively small (4.3 +/- 0.7 and 3.1 +/- 0.8 micrograms/dl [mean +/- SD), respectively, in young and old rats). In addition, no age-induced decrease in 3,5,3'-triiodothyronine levels was observed, suggesting that the aging process itself may be responsible for the changes in SR Ca2(+)-ATPase mRNA levels.

Depressed respiratory sinus arrhythmia: additional evidence for impairment of vagal activity in human hyperthyroidism.

The efferent activity of the parasympathetic component of the autonomic nervous system was evaluated by measuring the magnitude of the respiratory sinus arrhythmia in 3 female patients with hyperthyroidism (Basedow-Graves' disease) before and after treatment. The heart rate variations induced by the test increased in all patients after treatment of thyrotoxicosis (from 15 +/- 2.9 to 28.3 +/- 6.6 beats/min; mean +/- SEM) with propylthiouracil (600 mg/day). This result confirms our previous observations indicating an important and reversible impairment of the efferent vagal activity in human hyperthyroidism.

Depressed respiratory sinus arrhythmia: additional evidence for impairment of vagal activity in human hyperthyroidism

The efferent activity of the parasympathetic component of the autonomic nervous system was evaluated by measuring the magnitude of the respiratory sinus arrhythmia in 3 female patients with hyperthyroidism (Basedow-Graves' disease) before and after treatment. The heart rate variations induced by the test increased in all patients after treatment of thyrotoxicosis (from 15 + or - 2.9 to 28.3 + or - 6.6 beats/min; mean + or - SEM) with propylthiouracil (600 mg/day). This result confirms our previous observations indicating an important and reversible impairment of the efferent vagal activity in human hyperthyroidism

Autonomic control of heart rate during dynamic exercise in human hyperthyroidism.

1. The relative contribution of the sympathetic and parasympathetic components of the autonomic nervous system to the regulation of the chronotropic response to dynamic exercise was evaluated indirectly in nine patients with thyrotoxicosis and in seven normal volunteers. All subjects were women, with equivalent ages in both groups. Six of the nine patients with hyperthyroidism were reevaluated after clinical compensation of the disease with propylthiouracil. 2. Heart rate responses were evaluated during discontinuous dynamic effort maintained for 4 min on a bicycle ergometer at levels of 5, 15, 25 and 50 W, and also of 75 W in normal individuals. The study was also performed under conditions of sympathetic pharmacological blockade with propranolol (0.2 mg/kg body weight). 3. Even though the magnitude of the total increase in heart rate evoked by each level of dynamic exercise was equivalent in normal and hyperthyroid patients, the tachycardiac response occurring at the beginning of the exercise, which depends on a predominantly vagal mechanism, was substantially different from that observed after 30 s of effort, when sympathetic contribution becomes more important. The hyperthyroid patients showed considerably lower increases in heart rate than the normal individuals during the initial 30 s of effort, with the opposite occurring from this moment onward. 4. In the hyperthyroid patients, beta-adrenergic blockage depressed tachycardia after 30 s of effort at the 15 and 50 W levels, whereas in normal individuals this effect was only manifested at 50 and 75 W. 5. The patients who obtained clinical compensation showed a pattern of chronotropic response which tended to be close to that shown by normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple pulmonary thromboembolism diagnosed by two-dimensional echocardiography.

A 55-year-old man was admitted to our hospital because of progressive dyspnea, orthopnea and hemoptysis. Two-dimensional echocardiography multiple echo-dense images 1-4 mm in diameter were consistently seen crossing the tricuspid valve. A hypothesis of multiple pulmonary thromboembolism was raised. Clinical and postmortem evidence were later obtained to confirm this diagnosis.

The role of the autonomic nervous system in the resting tachycardia of human hyperthyroidism.

The mechanisms that control resting heart rate in hyperthyroidism were evaluated in six patients before and after treatment with propylthiouracil. The patients were subjected to pharmacological blockade under resting conditions in two experimental sessions: first session, propranolol (0.2 mg/kg body weight); second session, atropine (0.04 mg/kg body weight) followed by propranolol (0.2 mg/kg body weight). All drugs were administered intravenously. Resting heart rate was significantly reduced from 100 +/- 6.5 beats/min to 72 +/- 2.5 beats/min (P less than 0.005) after clinical and laboratory control of the disease. After double blockade, intrinsic heart rate was reduced from 105 +/- 6.8 beats/min before treatment to 98 +/- 6.0 beats/min after treatment (P less than 0.025). The reduction in heart rate caused by propranolol was not significantly different before (-13 +/- 1.4 beats/min) and after (-9 +/- 1.0 beats/min) propylthiouracil. In contrast, atropine induced a higher elevation of heart rate after treatment (45 +/- 8.6 beats/min) than before treatment (26 +/- 4.0 beats/min). The present results suggest no appreciable participation of the sympathetic component of the autonomic nervous system in the tachycardia of hyperthyroidism, at least under the conditions of the present study. The small change observed in intrinsic heart rate, although significant, seems to indicate that this is not the most important mechanism involved in this tachycardia. Our results suggest that an important reduction in the efferent activity of the parasympathetic component participates in the mechanisms that modify resting heart rte in hyperthyroidism.