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PubMed1998

Thyroid function in lead smelter workers: absence of subacute or cumulative effects with moderate lead burdens.

OBJECTIVE: To evaluate the effect of low to moderate occupational lead exposure on thyroid function we conducted a cross-sectional study of 151 male lead smelter workers. METHODS: Parameters of thyroid function were assessed in relation to both subacute and cumulative lead exposure over a 10-year employment period. Blood lead levels, obtained from plant surveillance records, were used to establish four ordinal levels of current and cumulative exposure (< 15, 15-24, 25-39, and > or =40 microg/dl). RESULTS: Mean values for the lowest as compared with the highest current exposure group were similar for thyroxine (T4: 6.8 versus 6.1 microg/dl), estimated free thyroxine (EFT4: 1.6 ng/dl in both groups), and thyroid-stimulating hormone (TSH: 1.8 versus 1.7 mIU/l); there was no evidence of a significant trend for diminished thyroid function associated with increasing current lead exposure. Similarly, no significant difference was observed for T4, EFT4, or TSH in relation to the 10-year cumulative exposure or for adjusted analyses controlling for potential confounders, including age and alcohol use. CONCLUSION: In contrast to studies observing thyroid dysfunction in the setting of high lead exposure and related clinical poisoning, our findings weigh against a significant physiologic effect on thyroid function at lower levels (< 60 microg/dl) of occupational lead exposure.

Adult↗
PubMed1994

Renal endothelin mechanism in altered thyroid states.

Endothelin (ET) mechanisms were studied in hyper- and hypo-thyroid states in rats. Hyperthyroidism was induced by daily administration of thyroxine (0.1 mg/kg, i.p.) for 8 weeks, while hypothyroidism was induced by daily administration of methimazole (10 mg/kg, i.p.) for 8 weeks. The concentration of endogenous ET-1 was determined in the kidneys using radioimmunoassay. Systemic hemodynamics and renal blood circulation was measured using a radioactive microsphere technique. A significant increase in systolic and diastolic blood pressure, heart rate and cardiac output was observed in hyperthyroid rats as compared to eu- and hypo-thyroid rats. Total peripheral resistance was found to be similar in eu-, hyper- and hypo-thyroid rats. The endogenous concentration of ET-1 in the kidneys was significantly lower in hyper- as compared to eu- and hypo-thyroid rats. The blood flow to the kidneys was significantly increased in hyper- as compared to eu- and hypo-thyroid rats. Infusion of ET-1 (100 ng/kg/min i.v. for 45 min) produced a significant decrease in blood flow to the kidneys of eu-, hyper- and hypo-thyroid rats. The decrease in blood flow was similar in eu-, hyper- and hypo-thyroid rats, indicating that the response of renal blood vessels to exogenous ET-1 is not altered during thyroid dysfunction. Since endogenous ET-1 is involved in the regulation of vascular tone, it may be concluded that in hyper-thyroid rats decrease in concentration of the renal ET-1 could be contributing to an increase in blood flow to the kidney.

Animals↗
PubMed1978

Recent developments in thyroid hormone metabolism: interpretation and significance of measurements of reverse T3, 3,3'T2, and thyroglobulin.

The development of specific radioimmunoassays has allowed measurements of 3,3',5'-triiodothyronine (reverse T3), 3,3'-diiodothyronine (3,3'T2), and thyroglobulin to be performed in serum and in various biological fluids both in normal and in altered states of thyroidal economy. The physiology, kinetics, and metabolic actions of reverse T3, 3,3'T2 and thyroglobulin are reviewed. Presently, it appears that reverse T3 and 3,3'T2 measurements in amniotic fluid and cord serum may potentially be useful in diagnosing fetal or neonatal thyroid dysfunction, and serum thyroglobulin measurements appear to be important as a measure of the efficacy of treatment of patients with differentiated thyroid carcinoma.

Amniotic Fluid↗
PubMed2005

Thyroid peroxidase autoantibodies in euthyroid subjects.

Thyroid peroxidase (TPO) is a key enzyme in the formation of thyroid hormones and a major autoantigen in autoimmune thyroid diseases. Titers of TPO antibodies also correlate with the degree of lymphocytic infiltration in euthyroid subjects, and they are frequently present in euthyroid subjects (prevalence 12-26%). Even within the normal range for thyrotropin (TSH), TPO antibody titers correlate with TSH levels, suggesting that their presence heralds impending thyroid failure. Assays for serum TPO antibodies have become much more sensitive, and very low titers can be found in virtually all subjects. However, titers above an assay-dependent cut-off are a clear risk factor for hypothyroidism; in the Whickham survey the annual risk of developing hypothyroidism in TPO-positive women with normal thyrotropin levels was 2.1%. Measuring TPO antibodies in euthyroid subjects can be used to identify subjects with increased risk for hypothyroidism: e.g. as triage to measure thyrotropin. This could be done in women who wish to become pregnant and those with an increased risk per se who are pregnant (to predict first trimester hypothyroidism, and postpartum thyroid dysfunction), patients with other autoimmune diseases, subjects on amiodarone, lithium, or interferon-alpha, and in relatives of patients with autoimmune thyroid diseases.

Autoantibodies↗
PubMed1985

Diagnosis of hyperthyroidism: the newer biochemical tests.

Investigation of suspected hyperthyroidism is conventionally based on measurement of total or free T4 as the initial test, followed in equivocal cases by total or free T3, and the TRH test. Recent developments in techniques for measuring free hormones and TSH promise to change this approach. Free T4 and free T3 can now be rapidly and simply quantitated in whole serum using labelled analogue radioimmunoassays. Specific and highly sensitive assays using labelled monoclonal antibodies are now available for serum TSH that permit the suppressed levels found in most cases of hyperthyroidism to be distinguished from euthyroid levels. These newer assays are available at a cost per test that is often similar to that of the more established tests. Available evidence indicates that measurement of basal serum TSH by a sensitive labelled antibody method can serve as a first line test, at least in uncomplicated cases of suspected hyperthyroidism. In patients with a suppressed TSH, a serum free T4, and in equivocal cases free T3, will distinguish the clinical and subclinical forms of hyperthyroidism. Such an approach would obviate the need for the TRH test. It must be emphasized, however, that experience with this new approach is limited. Caution is advised in the interpretation of low TSH and free hormone levels when there are associated complicating features, such as severe non-thyroidal illness, or pregnancy. These developments mark a trend in thyroid function testing away from measurement of circulating total hormone levels. The newer tests provide an assessment of end organ (thyrotroph) response, and an assessment of biologically active (free) hormone to which the tissues are exposed. These complementary approaches have the potential to identify relatively minor degrees of thyroid dysfunction.

Diagnosis, Differential↗
PubMed2006

Thyroid function abnormalities and antithyroid antibody prevalence in pregnant women at high risk for gestational diabetes mellitus.

Both gestational diabetes mellitus (GDM) and thyroid dysfunction in pregnancy compromise maternal and fetal health. The aim of the present study was to determine the prevalence of abnormal thyroid function and antithyroid antibodies during early pregnancy in a population at high risk for GDM. Serum free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH) were measured in 301 pregnant women who underwent routine 'universal screening' for GDM. The antithyroid peroxidase antibody (antiTPOAb) was also quantified in 255 of these women. GDM was confirmed by a 75-g oral glucose tolerance test using World Health Organization criteria. No statistically significant difference was found between the 80 (26.6%) women with GDM and the 221 (73.4%) women without GDM for any of the thyroid function tests. In the cohort tested for antiTPOAb, the 51 (20.0%) women who were positive for antiTPOAb had higher mean TSH (1.57 +/- 2.49 mIU/l; p < 0.001) than the women negative for antiTPOAb. Seventeen (5.6%) women had low FT4 while 12 (4.0%) women had high TSH; 28 (9.3%) women had low serum TSH, among whom three (1.0%) also had high FT4. The significantly higher prevalence of hypothyroxinemia and antiTPOAb titers than generally reported warrants routine screening for thyroid abnormalities. This screening, which can be effectively and easily incorporated into screening practices already in place for GDM, would result in improved obstetric care.

Adult↗
PubMed1991

Thyroid hormone concentrations in Nepal: a study of potential Gurkha army recruits. The effect of changes in diet.

A group of non goitrous, potential Gurkha army recruits were tested in Nepal for serum free triiodothyronine (fT3), free thyroxine (fT4) and thyrotropin (TSH) concentrations. Twenty-five percent of the men were recruited into the army and urine samples taken for analysis of iodine and creatinine. Twenty per cent of the recruits underwent thyrotropin releasing hormone (TRH) stimulation tests. After ten months basic training on a diet considered to be iodine sufficient, the tests were repeated on the same men. The results were also compared to army recruits in the UK. All the potential Gurkha recruits had higher serum levels of thyroid hormones than the UK recruits. Some regional differences were found with those men from the Western recruiting depot having lower fT4 and higher TSH concentrations. Urinary iodine and creatinine concentrations showed evidence of slight relative malnutrition and iodine deficiency which was more pronounced in the Western depot. TRH stimulation tests showed no evidence of thyroid dysfunction but highlighted the differences between the Eastern and Western groups. After ten months on an iodine sufficient diet the serum thyroid hormone concentrations became closer to those of the UK recruits, showing any differences to be reversible. The results from the two Gurkha groups became similar which was reflected in the urine analysis results.

Adolescent↗
PubMed2000

Thyroid function and obesity in children and adolescents.

The aim of this retrospective study was to investigate the frequency of thyroid dysfunction as assessed by TSH, T3 and T4 in a large cohort of 290 obese and 280 healthy children. In addition, thyroid autoantibodies were measured in random subgroups of 123 obese and 80 control children, iodine excretion in 50 and thyroid volume in 23 of the obese children. Elevated TSH levels (>4 U/l) were found in 22 obese children (7.5%), but only in one control (0.3%). The medians of TSH and T3 concentrations were normal, but significantly higher in the obese group than in the controls, while T4 levels did not differ. The prevalence of positive thyroid autoantibodies was increased in the obese children, for the most part in those with elevated TSH. There was no evidence for iodine deficiency as a cause of the average increase of TSH. We conclude that in childhood obesity TSH and T3 levels are significantly increased; in most cases, however, these increases are not accounted for by thyroid autoimmunity or iodine deficiency. As a consequence, TSH elevations with normal thyroid hormone levels in obese children don't need any thyroxine treatment, if thyroid disorders were definitely excluded beforehand.

Adolescent↗
PubMed2003

Endocrinological disturbances in chronic obstructive pulmonary disease.

In this overview, the available literature on endocrinological disturbances in chronic obstructive pulmonary disease (COPD) is reviewed, with stress on growth hormone/insulin-like growth factor I (IGF-I), thyroid hormone and the anabolic steroids. In COPD, little is known about circulating growth hormone or IGF-I concentrations. Some authors find a decrease in growth hormone or IGF-I, others an increase. An increase of growth hormone might reflect a nonspecific response of the body to stress (for instance, hypoxaemia). Until now, only one controlled study on growth hormone supplementation has been published, which however did not reveal any functional benefits. Before growth hormone supplementation can be advised as part of the treatment in COPD, further controlled studies must be performed to investigate its functional efficacy. The prevalence of thyroid dysfunction in COPD and its role in pulmonary cachexia has not been extensively studied. So far, there is no evidence that thyroid function is consistently altered in COPD, except perhaps in a subgroup of patients with severe hypoxaemia. Further research is required to more extensively study the underlying mechanisms and consequences of disturbed thyroid function in this subgroup of COPD patients. A few studies have reported the results of anabolic steroid supplementation in chronic obstructive pulmonary disease. Although some studies have discerned that low circulating levels of testosterone are common in males with chronic obstructive pulmonary disease, little is known about the prevalence, the underlying causes or functional consequences of hypogonadism in these patients. The use of systemic glucocorticosteroids and an influence of the systemic inflammatory response have been suggested as contributing to low testosterone levels. It can be hypothesised that low anabolic hormones will reduce muscle mass and eventually result in a diminished muscle function. Further evidence is required before testosterone replacement can be recommended for males with chronic obstructive pulmonary disease.

Anabolic Agents↗
PubMed1995

Commonly asked questions about thyroid function.

Thyroid function abnormalities in asymptomatic outpatients are common. When a patient is found to have an abnormality in thyrotropin (thyroid-stimulating hormone) or free or total thyroxine (T4), a review of the patient's medications and a careful neck examination will usually provide the explanation. Further diagnostic laboratory studies should include additional tests of T4 or thyrotropin. Determining the presence of antimicrosomal antibodies is useful for further assessment of "subclinical" hypothyroidism, and measures of protein binding (T4-binding capacity or T4-binding protein electrophoresis) help confirm a suspected congenital or acquired abnormality of T4 binding. Recognition of euthyroid hypothyroxinemia and hyperthyroxinemia is important in order to avoid intervention with inappropriate treatment. Management of subclinical hypothyroidism and hyperthyroidism necessitates clinical judgment about the patient's symptom profile and risks for long-standing or progressive thyroid dysfunction.

Humans↗
PubMed1983

Thyroid disease in hemochromatosis. Increased incidence in homozygous men.

The thyroid function of 49 patients homozygous for the hemochromatosis allele was studied by measurement of serum thyroxine and thyrotropin concentrations. Of 34 homozygous men, three were found to be hypothyroid (thyroxine, less than 3.0 micrograms/dL and thyrotropin, greater than 40 ImU/mL) and one was hyperthyroid (thyroxine, 24 micrograms/dL). All 15 homozygous women had normal thyroid function. The hypothyroid patients had elevated titers of antithyroid antibodies. Histologic examination of the thyroid at autopsy of one hypothyroid patient showed notable iron accumulation and fibrosis with modest lymphocytic infiltration. The causative importance of iron deposition in thyroid diseases associated with hemochromatosis was suggested by the reversal of the usual sex ratio of thyroid dysfunction. Men with hemochromatosis had a much greater iron load than women, and they also had a surprisingly higher incidence of thyroid disease. Iron may have caused injury to the thyroid, followed by the development of antithyroid antibodies and hypothyroidism. The frequency of thyroid disorders in men with hemochromatosis is about 80 times that of men in the general population.

Adult↗
PubMed1991

Testicular dysfunction with amiodarone use.

Amiodarone, an antiarrhythmic drug approved for use in patients who survive cardiac arrest, has been associated with infiltration of or inflammatory changes in various tissues. To date thyroid dysfunction has been the only endocrine disturbance noted. In an initial group of seven amiodarone-treated men undergoing evaluation for sexual dysfunction, an elevation in serum gonadotropin concentration was detected, suggesting testicular dysfunction. Because of this finding, gonadal function was prospectively evaluated in 44 men (18 who had been treated with amiodarone for greater than 1 year and 26 survivors of cardiac arrest who had been treated with antiarrhythmic drugs other than amiodarone). Amiodarone-treated men had higher serum follicle-stimulating hormone (41.8 +/- 22.8 vs. 14.4 +/- 10.4 mIU/ml, p less than 0.001) and luteinizing hormone (34.8 +/- 26.4 vs. 10.1 +/- 5.2 mIU/ml, p less than 0.001) concentrations compared with control subjects. Although serum total and free testosterone levels were comparable between the two patient groups, these levels were inversely correlated (r = -0.53, p less than 0.05; r = -0.62, p less than 0.01, respectively) with cumulative amiodarone dose. Hyperresponsiveness to the administration of gonadotropin-releasing hormone was noted in the 10 amiodarone-treated men evaluated by this diagnostic test. Sexual dysfunction was common in both groups (70% of control subjects and 82% of amiodarone-treated subjects), although atrophic testes were more commonly observed in amiodarone-treated men (p less than 0.05). Because of the elevated serum gonadotropin level, it is concluded that testicular dysfunction may result from prolonged amiodarone treatment.

Adult↗
PubMed1990

Clinical aspects of Down syndrome from infancy to adulthood.

In past decades, most individuals with Down syndrome were usually not afforded adequate medical care. Many children with Down syndrome were institutionalized and they were often deprived of all but the most elementary medical services. Fortunately, there have been major improvements in the health care provision during the past 20 years. Professionals who are providing services to persons with Down syndrome need to be aware of those clinical conditions that are more often observed in this population. Certain congenital anomalies (congenital cataracts, anomalies of the gastrointestinal tract, and congenital heart disease) often require immediate attention, as some of them may be life threatening. During the subsequent childhood years a number of clinical conditions and disorders such as infectious diseases, increased nutritional intake, periodontitis, seizure disorders, sleep apnea, visual impairment, audiologic deficits, thyroid dysfunction, and skeletal problems usually occur at a higher prevalence. During adolescence specific aspects of maturation and certain health issues (skin infections, thyroid disorders, increased weight gain, and others) as well as mental health concerns need to be taken into consideration. Similar concerns may also be observed during adulthood which in addition is often marked by accelerated aging and the threat of Alzheimer disease in some persons with Down syndrome. Special attention needs to be paid to these disorders and conditions during the lifetime of a person with Down syndrome. Appropriate medical care should be provided to and no form of treatment should be withheld from a person with Down syndrome that would be given unhesitatingly to an individual without this chromosome disorder.

Adolescent↗
PubMedDate not supplied

Graves' ophthalmopathy. A clinical and immunologic review.

Graves' thyroid disease and the orbitopathy which often accompanies it have puzzled physicians and scientists for more than 150 years. Although certain histopathological features have been documented, it is not known what mechanisms are responsible for the systemic and/or ocular disorders. The ocular condition characteristic of Graves' disease may exist in the absence of clinical or biochemical evidence of thyroid dysfunction, and when the systemic and ocular condition exist together, they may follow completely different clinical courses. Because the relationship between the thyroid disorder and the orbitopathy is not established, the authors refer not to "thyroid ophthalmopathy," but to "Graves' ophthalmopathy." In this review, histopathological features of Graves' ophthalmopathy are reviewed. The differential diagnosis of the ophthalmopathy and approaches to its evaluation are discussed, notably the T-4 radioimmunoassay, T-3 resin uptake and TSH tests, as well as CT scanning and ultrasonography. The characteristics of Classes 0-6 ophthalmopathy are outlined and the management of cases in each class is considered. The possible immunological basis for Graves' ophthalmopathy is also reviewed.

Eye Diseases↗
PubMed1993

Lithium-associated transient thyrotoxicosis in 4 Chinese women with autoimmune thyroiditis.

Four Chinese female patients who suffered from manic-depressive disorder and underlying autoimmune thyroiditis developed transient episodes of thyrotoxicosis during maintenance lithium therapy. Endocrinologically speaking, three of them had "Hashitoxicosis", while the other had silent lymphocytic thyroiditis. Albeit rare among Western patients, such lithium-associated thyroid dysfunctions appeared to be more likely to occur in Hong Kong Chinese. They seemed to involve multiple aetiological factors, such as autoimmune thyroid disease, the toxic and immunomodulatory roles of lithium and perhaps genetic and dietary factors. Because of their self-limiting nature, the importance of avoiding unnecessary and potentially deleterious antithyroid treatment is emphasised.

Adolescent↗
PubMed1991

Incidence and prevalence of thyroid disease in elderly women: results from the longitudinal population study of elderly people in Gothenburg, Sweden.

The incidence and prevalence of thyroid dysfunction were estimated in a longitudinal study of a representative sample of elderly women at ages 70, 75, 79 and 81. Thyroid-stimulating-hormone concentrations were measured in frozen samples obtained at the ages of 70 and 75 that had been stored for ten and five years, respectively. At the ages of 79 and 81 the serum concentrations of thyroid-stimulating hormone were determined in connection with the sampling. For comparison, thyroid-stimulating-hormone concentrations were also measured in another representative population sample of women at ages 70 (n = 297) and 76 (n = 342), in whom measurements were carried out in direct connection to the clinical study. History of previous thyroid disease, e.g. thyroid surgery and thyroid hormone treatment, was obtained through a questionnaire. Information about previous treatment with radio-iodine was obtained from records. At the age of 70, 1.9% had had thyroid surgery but none had been treated with radio-iodine. L-Thyroxine had been prescribed for 3.5%, and another 3.9% had high thyroid-stimulating-hormone concentrations (greater than 10.0 mU/l) indicating thyroid hypofunction. Between 70 and 79 years of age, eight of the 514 women had developed high concentrations of thyroid-stimulating hormone and another two women had received treatment with L-thyroxine. Three women had received radio-iodine therapy. In addition, one woman at the age of 81 was discovered to have hyperthyroidism. The retrospective analysis showed that markedly elevated TSH concentrations had been present in several women for at least nine years.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

Thyroid autoantibodies in hospitalized chronic geriatric patients: prevalence, effects of age, nonthyroidal clinical state, and thyroid function.

OBJECTIVE: To investigate the effect of age, clinical condition, and thyroid function on the prevalence of thyroid autoantibody positivity in hospitalized chronic geriatric patients. DESIGN: A screening study of hospitalized chronic geriatric patients. PARTICIPANTS: 249 non-selected, hospitalized, chronic geriatric patients more than 60 years of age and 81 20 to 40-year-old healthy persons. MEASUREMENTS: Thyrotropin (TSH); thyroxine (T4) and free thyroxine (FT4); and triiodothyronine (T3), thyroglobulin (Tg), antibodies against thyroid peroxidase (AbTPO) and antibodies against thyroglobulin (AbTg) estimation in a screening study. RESULTS: AbTPO positivity (AbTPO+) was found more often than AbTg positivity (AbTg+) (15.3% vs 9.2%, P = .04), one being positive (Ab+) in 19.3%. The occurrence was higher in females than males (Ab+:27.1% vs 7.1%, P < .001; AbTPO+:21.9% vs 5.1%, P < .001; AbTg+:13.2% vs 3.1%, P = .0052). Among the Ab+ patients, AbTPO was more often positive than AbTg (40/48 vs 21/48, P < .001). The sensitivity, specificity, and positive predictive value of Ab positivity to detect a thyroid disorder were 0.35, 0.85 and 0.38, respectively. Within the population of euthyroid geriatric patients, the occurrence of AbTg+ (chi 2(2) = 8.65, P = .013) and Ab+ (chi 2(2) = 8.02, P = .018) correlated positively with the age of the patients, and there was also a female predominance (AbTPO+ 18% vs 3.7% in the males; AbTg+ 13% vs 2.4%; Ab+ 25.8% vs 6.1%). When compared with 20 to 40-year-old subjects, only the euthyroid > or = 80-year-old patients showed a significantly higher occurrence of Ab+ (26.2% vs 9.9% chi 2(1) = 5.64, P = .017). In the euthyroid > or = 80-year-old females, AbTPO+ was 25%, AbTg:22.2%, and Ab+: 36.1%!. The nonthyroidal clinical state of the euthyroid patients did not correlate with the antibody prevalence. CONCLUSIONS: In hospitalized chronic geriatric patients, AbTg and especially AbTPO positivity is frequent, even in euthyroid patients without goiter. This aspecific Ab positivity in the euthyroid state correlates to the age, but not to the severity of the nonthyroidal clinical condition of the patients and explains why the Ab positivity is not predictive enough for thyroid dysfunction in this subpopulation. Thus, in hospitalized chronic geriatric patients the AbTg and AbTPO titers should be examined only in cases where thyroid screening (TSH) reveals abnormal results.

Adult↗
PubMed1991

Autoimmune thyroiditis following interleukin-2 and LAK cell therapy for metastatic renal cell carcinoma: correlation with tumor regression.

A 63-year-old woman receiving recombinant interleukin-2 (rIL-2) + lymphokine activated killer cells for metastatic renal cell carcinoma developed autoimmune thyroiditis with clinical hypothyroidism and high titer anti-thyroglobulin and anti-microsomal antibodies. The onset of thyroid dysfunction was associated with tumor regression and resulted in complete response at the end of the treatment. Cytologic and cytofluorimetric studies on thyroid tissue showed two distinct populations, mainly consisting of small lymphocytes and large thyrocytes, and the latter expressed MHC class II antigens. After completion of rIL-2 treatment, hypothyroidism gradually decreased until resolution; complete tumor remission lasted 18 months. Mechanisms underlying the association between autoimmune thyroiditis and cancer regression are discussed.

Carcinoma, Renal Cell↗