Clinical and pathological significance of asymptomatic atrophic thyroiditis. A condition of latent hypothyroidism

Asymptomatic Hypothyroidism and Hypercholesterolemia

Hypothyroidism is a cause of secondary hyperlipidaemia. This study investigates the frequency of biochemically diagnosed hypothyroidism and its relationship with plasma cholesterol concentration in apparently healthy people.

Thyroid function tests (total T4, TSH, and free T4) were performed on 272 apparently healthy men and women (179 vegetarians, 93 meat eaters) with a plasma cholesterol concentration above 7 mmol/l and on 90 individuals with a plasma cholesterol below 4.1 mmol/l who were matched for age, sex and dietary habits.

Six per cent of those with a plasma cholesterol above 7 mmol/l had biochemical evidence of hypothyroidism as defined by a TSH greater than 10 mIU/l (reference range 1–6) and a low free T4 below 10 pmol/l (reference range 10.1–25). Eighty per cent of these people had a high titre of thyroid anti-microsomal antibodies. Of the 90 individuals with a plasma cholesterol level below 4.1 and the 25 randomly selected participants none had biochemical evidence of hypothyroidism.

Hypothyroidism is relatively common in apparently healthy people with a raised plasma cholesterol. It appears no commoner in vegetarians than in meat eaters.

Central hypothyroidism in a patient with pituitary autoimmunity: evidence for TSH-independent thyroid hormone synthesis

CONTEXT

Acquired central hypothyroidism is rare, especially when isolated, and is typically associated with detectable, although biologically inactive, serum TSH.

OBJECTIVE

We describe a 56-yr-old woman with profound central hypothyroidism and partial central hypoadrenalism, in the absence of other endocrine abnormalities. In contrast to most cases of central hypothyroidism, serum TSH remained undetectable for 9 months before the initiation of thyroid hormone and hydrocortisone treatment. A test for pituitary autoantibody was moderately positive. Serum free T(4), serum T(3), and neck radioiodine uptake were low but detectable. The thyroid and pituitary glands appeared morphologically normal on neck ultrasound and head magnetic resonance imaging, respectively.

SETTINGS

The study was conducted in a tertiary academic medical center.

CONCLUSIONS

This case illustrates the variable clinical presentation of pituitary autoimmunity. The persistence of low but detectable thyroid hormone levels and radioiodine neck uptake in the absence of TSH suggests that significant TSH-independent thyroid hormone synthesis may occur in the normal thyroid.

[Thyroid dysfunction in women with suspected fibromyalgia]

BACKGROUND AND OBJECTIVE

Due to its prevalence, morbidity, and frequency rate, fibromyalgia (FM) represents a health problem and produces high healthcare resource utilization. Serum thyrotropin (TSH) measurement is recommended as a first-line laboratory test to exclude hypothyroidism as a cause of FM syndrome. The aim of this study was to analyze the prevalence of thyroid dysfunction (TD), the frequency of TSH measurement, the effect of levothyroxine treatment, and whether screening for TD is justified in women with suspected FM.

PATIENTS AND METHODS

A cross-sectional descriptive study was performed in 400 consecutive female outpatients with suspected FM and in 384 controls from January 2001 to October 2004. TSH measurement was used as the first line test to detect TD.

RESULTS

The prevalence of TD in patients with suspected FM (40/400; 10%; 95% CI: 7-13%) and controls was similar (46/384; 12%; 95% CI: 9-15%). No differences were found in the types and grades of TD. The prevalence of TD was higher in patients with suspected FM and connective tissue diseases (12%) than in those without these diseases (5%). The most frequent TD was subclinical hypothyroidism (5.5% in suspected FM and 6.7% in controls), and in 93% of these cases TSH concentrations were <10 mIU/L. FM persisted in all women with hypothyroidism even after euthyroidism was achieved with levothyroxine. A total of 870 TSH determinations were performed in 360 euthyroid patients with suspected FM.

CONCLUSIONS

The prevalence of TD in women with suspected FM does not differ from that in the general population. Screening for TD does not appear to be justified in women without diseases that increase their risk. In many cases the request for thyroid function tests is excessive. Treatment for hypothyroidism does not affect FM.

Subclinical hypothyroidism: a review of neuropsychiatric aspects

The authors review current information about the prevalence, causes, course, and consequences of subclinical hypothyroidism. There is evidence that subclinical hypothyroidism may be associated with cognitive dysfunction, mood disturbance, and diminished response to standard psychiatric treatments. Recommendations are presented for the screening, evaluation and treatment of patients in whom subclinical hypothyroidism may be contributing to neuropsychiatric dysfunction.

The genetics of Hashimoto's disease

Despite strong epidemiologic evidence in favor of a genetic component in the etiology of HT, few hereditary risk factors have been consistently identified. These factors include the HLA and CTLA-4 genes. The mechanisms by which these genes confer increased susceptibility to HT are unclear. The identification of these genes has failed to explain completely the large hereditary effect observed in families of patients. More substantial genetic determinants must be hidden in the folds of the human genome and will most likely be detected in the near future. The powerful approach of linkage analysis will be supported by advancements in the description of the human genome and by technologic improvements in the ability to process large amounts of biologic data. Knowledge of such determinants will provide predictive tools to be used on clinical grounds and invaluable insight into the pathogenesis of this puzzling disease.

Clinical significance of measurements of antithyroid antibodies in the diagnosis of Hashimoto's thyroiditis: comparison with histological findings

Measurements of antithyroglobulin and antimicrosomal (antiperoxidase) antibodies have been performed widely for the clinical diagnosis of autoimmune thyroid diseases. The present study was designed to compare these antibody titers with histological findings of the thyroid in patients with diffuse goiter who were suspected of having Hashimoto's thyroiditis. One hundred and ten euthyroid or hypothyroid patients (10 males and 100 females; age 48 +/- 15 (SD) years old) with diffuse goiter were studied for the measurement of antithyroglobulin and antimicrosomal or antiperoxidase antibodies by a hemagglutination technique (TGHA and MCHA, respectively) and by a newly developed radioassay (TgAb and TPOAb, respectively). The antibody titers were compared with the histological findings obtained by needle biopsy. TgAb, TPOAb, TGHA, and MCHA were detected in 80 (96.4%), 61 (73.5%), 37 (44.6%), and 54 (65.1%) of 83 patients with histologically proven Hashimoto's thyroiditis, respectively, but in only one (3.7%) of 27 patients without any inflammatory changes in the biopsy specimen. In 55 patients with negative TGHA and MCHA, the TgAb positivity was more closely associated with the histological diagnosis of Hashimoto's thyroiditis than the TPOAb positivity was, the incidence of each antibody in Hashimoto's thyroiditis being 89.7% (26/29) and 27.6% (8/29), respectively. In conclusion, the histological diagnosis of Hashimoto's thyroiditis can most precisely be predicted by the newly developed radioassay for TgAb.

[Thyroid function and dysfunction in the elderly]

The consequences of aging function are appreciated in various ways. In fact most of the thyroid hormone abnormalities described in the elderly are secondary to associated disease or treatments. Health and nutritional status seem to be more determinant than age. However, there is an increased prevalence of dysthyroidism in the elderly. Symptoms may be misleading and induce severe general repercussions. Mild or occult forms of dysthyroidism characterized by abnormal TSH levels with normal free thyroid hormone levels are not uncommon. Their clinical significance and their prognosis without treatment are still unresolved. The frequency of dystrhyroidism during old age and the possibility of a specific treatment may be in favour of a screening by a systematic TSH determination in elderly patients.

Assessment of antibody dependent cell cytotoxicity in autoimmune thyroid disease using porcine thyroid cells

Antibody Dependent Cell Cytotoxicity (ADCC) appears to be involved in Autoimmune Thyroid Disease (AITD). Homologous system may trigger non-specific reactions which might obscure specific ADCC. Heterologous target cells may be useful for studying ADCC, provided relevant antigen(s) are expressed. We therefore tested the capacity of porcine thyroid cells to elicit ADCC reaction in the presence of sera from various patients with AITD. Porcine thyroid cells were used in a 4-hr chromium release assay in the presence of 1/10 heat inactivated human sera and human peripheral blood lymphocytes at a 30:1 effector-target ratio. There was a significant correlation (r = 0.64; P < 0.01) between ADCC activities tested on human or porcine thyroid cells. Serum or IgG effects on porcine thyroid ADCC were dose-dependent between 1/10 to 1/10,000 dilutions. Non-thyroid cell systems were unaffected by thyroid cytotoxic sera. Porcine thyrocyte susceptibility to ADCC peaked at the fourth day of culture and was enhanced by addition of TSH or TSH and methimazole in the culture medium. Using this heterologous system, we demonstrated ADCC activity in a significant proportion of patients with thyroiditis (14/19), Graves' opthalmopathy (19/44) or of mothers of children with congenital hypothyroidism (14/39) and in the children themselves (15/39). Discrepancies observed in some sera between ADCC activity and antithyroperoxidase antibody suggest that thyroperoxidase is not the only antigen involved in ADCC. These results indicate that porcine thyroid cells appear suitable for ADCC assay in patients with AITD. Also this system should be helpful to characterize the antigen-antibody involved.

Increased mean serum thyrotropin in apparently euthyroid hypercholesterolemic patients: does it mean occult hypothyroidism?

Serum thyroid hormones and antithyroid autoantibodies (AAB) were assayed in 87 randomly selected hypercholesterolemic persons compared to 80 controls with normal serum total cholesterol (TC). Of the 87 hypercholesterolemic persons 22 (25%) had positive AAB compared to 5 (6%) controls. Furthermore, 8 of the hypercholesterolemic patients had a serum TSH level above 5 mU/l, i.e. the had subclinical hypothyroidism, not diagnosed before, whereas thyroid function was normal in all normocholesterolemic persons. The new and unexpected finding was that the hypercholesterolemic persons had on average a significantly higher serum TSH than the controls, and this was true even when persons with positive AAB were excluded. There was a significant correlation between TC and serum TSH. It is concluded that hypothyroidism may not be an all-or-none phenomenon, and that many hypercholesterolemic persons with thyroid tests within the conventional normal range may have a slight impairment of their thyroid function.

Thyroid stimulating hormone elevation without antithyroid antibody elevation in nursing home patients

OBJECTIVES

To investigate the relationship between antithyroid antibody elevation and thyrotropin (TSH) elevation.

SETTING

Large state veterans home.

METHODS

Seven hundred seventy-six residents were screened for TSH elevation. Seventy-two residents with TSH elevation and no history of thyroid disease or recent iodine exposure later had determinations of antithyroglobulin and antimicrosomal antibodies. The relationship between TSH levels and antibody titers was explored.

RESULTS

Eleven percent of the residents had TSH elevation. Thirty-two percent of men and 64% of women with TSH elevation had elevation of antithyroid antibodies. Those residents with the highest antithyroid antibody titers had significantly greater TSH elevation.

CONCLUSION

Previous investigators have found similar percentages of individuals with TSH elevation who lack antithyroid antibody elevation. We hypothesize that TSH elevation without elevated antibody titers may be the result of a previously described involutional histologic lesion of the thyroid.

Follow-up of mild hypothyroidism in a nursing home

The course of untreated mild hypothyroidism was followed in 67 nursing home residents (mean age 78 years). The diagnosis was based on a normal free thyroxine index (FTI) and elevated thyrotropin concentration (TSH 4.6 to 15.0 microIU/mL, nl less than or equal to 4.5 microIU/mL. FTI and FSH were measured in follow-up 42-378 (mean 161) days after the diagnosis of mild hypothyroidism had been made. In 45 patients initial TSH was less than 6.8 microIU/mL; in 23 of these subjects TSH returned to normal during the observation period, whereas in 22 TSH remained elevated. In all 22 residents whose initial TSH was greater than 6.8 microIU/mL, TSH remained elevated at follow-up. In 4 subjects whose initial TSH concentrations ranged from 5.0 to 9.6 microIU/mL, FTI fell below normal 91-141 days after the diagnosis of mild hypothyroidism was made. Clinical progression of the signs or symptoms of hypothyroidism was not detected in the 4 patients who developed hypothyroxinemia. Three demonstrated positive thyroid antibody titers, and 1 had myasthenia gravis. These observations suggest a need for replacement therapy in debilitated patients with mild hypothyroidism and evidence of thyroid autoimmunity.

Thyroid disease in the elderly

As people in our society live longer, it is important for clinicians to know more about problems commonly seen in the elderly. Thyroid problems are especially important to understand because they do occur with rather high frequency, and their mode of presentation is frequently different from those seen in younger patients. The thyroid gland does undergo certain age-related changes in anatomy and physiology, but overall the thyroid is able to produce a normal amount of thyroid hormone throughout the years. Hypothyroidism is frequently difficult to diagnose in the elderly, because many of the symptoms of hypothyroidism can easily be confused with symptoms of aging. When hypothyroidism is looked for in large population studies of elderly patients, the incidence varies from 1% to as high as 17%, with women being more commonly affected than men, and subclinical hypothyroidism being more common than overt hypothyroidism. Virtually all cases of hypothyroidism are due to autoimmune thyroid disease, with most patients having measurable titers of thyroid autoantibodies. The therapy of hypothyroidism is done with extreme caution, as older patients are frequently very sensitive to the effects of excess thyroid hormone. In addition, the metabolism of thyroid hormone slows down with age, making the full replacement dose much less in an older patient than in a younger one. Hyperthyroidism is also quite common, occurring in from 0.5% to 3% of all elderly patients. The presentation is frequently atypical, as patients often lack the hyperdynamic symptomatology and instead have a more sedated, apathetic presentation. Weight loss and cardiac symptoms frequently predominate, and the presence of a goiter is frequently absent, making the diagnosis less obvious than in a younger patient. Therapy is usually radioactive iodine, after an adequate course of antithyroid drugs, to render the patient euthyroid. Thyroid nodules do occur with increasing frequency in the elderly, but most of them are not malignant. Fine-needle aspiration for cytology is very helpful in determining which patients should be referred for surgery. Well-differentiated cancers do predominate, but their course is frequently less predictable than in younger patients. Lymphoma of the thyroid and undifferentiated cancers do occur with increasing frequency in the elderly. Multinodular goiter, usually of longstanding, is frequently seen in elderly patients, and thyroid hormone suppressive therapy not only is not indicated but may contribute to exogenous hyperthyroidism.

The presence of antithyroid antibodies in patients with affective and nonaffective psychiatric disorders

We determined the frequency of antithyroglobulin and antimicrosomal antibodies in 173 consecutively admitted psychiatric inpatients. (We found antithyroid antibodies in 8% (5/65) of patients with DSM-III major depression, 13% (4/31) with biploar disorder, and in 0% (0/4) of those with schizoaffective disorder.) The rate of antibody occurrence was unrelated to lithium exposure either within individual diagnostic categories or for the sample as a whole. The overall frequency of positive antithyroid antibody titers in patients with DSM-III affective disorder, 9% (9/99), did not differ from that in patients with nonaffective disorders, 10% (7/68). However, patients with bipolar affective disorder-mixed or bipolar affective disorder-depressed had a higher rate of positive antithyroid antibody titers than other patients. Our findings confirm earlier reports that thyroid disorders may be particularly common in patients with bipolar affective disorder, even in the absence of lithium exposure. However, as antithyroid antibodies also occurred at a relatively high rate in nonaffective disorders, the possible psychiatric effects of autoimmune thyroiditis do not appear to be limited to affective dysregulation.

Prevalence of thyroid disorders in psychogeriatric inpatients. A possible relationship of hypothyroidism with neurotic depression but not with dementia

Thyroid disorders are known to manifest occasionally as isolated psychiatric disorders. In order to determine whether thyroid dysfunctions could play a significant role in the pathogenesis of psychiatric disorders in the elderly, the prevalence of thyroid disorders was compared in a group of psychogeriatric patients and in a group of nonpsychiatric elderly patients. Thyroid function screening was performed in 157 patients consecutively admitted to a psychogeriatric unit, and the prevalence of hypothyroidism was determined in the different groups of psychiatric disorders (senile and multi-infarct dementia, organic brain syndrome of other etiologies, psychotic depression, neurotic depression, chronic delusional state, acute confusional state, and personality disorder). Thyroid function screening was performed similarly in 104 unselected elderly patients admitted to the medico-surgical admission unit of the University hospital to assess the prevalence of hypothyroidism in a general, nonpsychiatric, elderly population. Eight patients were diagnosed as hypothyroid based on an elevated basal thyrotropin (TSH) and on thyrotropin-releasing hormone (TRH) test in the total number of patients, two in the nonpsychiatric and six in the psychiatric group. Three had clinical hypothyroidism, with decreased total and free T4 and T3 plasma levels in addition to increased basal TSH, five had biochemical hypothyroidism, with normal T4 and T3 levels and an excess TSH response to oral TRH. The prevalence of hypothyroidism in the two groups did not differ significantly (1.9% in the nonpsychiatric versus 3.8% in the psychiatric group). The prevalence of hypothyroidism in a subgroup of 88 patients with senile and multi-infarct dementia was 2.3%.(ABSTRACT TRUNCATED AT 250 WORDS)

A high prevalence of thyroglobulin autoantibodies in adults with and without thyroid disease as measured with a sensitive solid-phase immunosorbent radioassay

Sera from 228 patients with thyroid disease and 140 healthy subjects without clinical or biochemical evidence of thyroid disease, were tested using a sensitive solid-phase immunosorbent radioassay (RIA) and a passive hemagglutination test (TRC test) for thyroglobulin antibodies (Tg-ab). With the RIA technique, Tg-ab was found in 27% of the controls (36% of the women and 15% of the men), whereas only 0.7% of them were Tg-ab positive with the TRC test. All individuals with primary hypothyroidism were Tg-ab positive with the RIA, compared with only 56% with the TRC test. Tg-ab (RIA) were found in 43/53 (81%) of the patients with toxic diffuse goiter, and in 30-40% of the patients with toxic nodular goiter, toxic adenoma, atoxic goiter, and thyroid carcinoma, the TRC test being positive in 10-17% of these patients. The high prevalence of Tg-ab in the healthy population suggests that subclinical thyroiditis is more frequent than has been assumed from antibody measurements made with less sensitive methods, and is in agreement with the prevalences reported from autopsy studies.

Natural history of primary myxedema

It is generally admitted that primary myxedema in adults is the outcome of autoimmune atrophic thyroiditis. The present review traces the natural history of this process from its incipient biologic and genetic anomalies up to its protracted asymptomatic course, clinical development, and eventual lethal complications. The apprehension of preclinical hypothyroidism may change a clinician's outlook on early diagnosis and therapy.

Relationship of circulating thyroid antibodies to coronary artery disease

A study of the relationship between circulating thyroid antibodies and coronary artery disease was performed. In 180 patients, the state of the coronary arteries was determined by cardiac catheterization and antithyroglobulin and antimicrosomal antibodies were measured using immunoprecipitation. The prevalence of risk factors for coronary artery disease and the mean age of the groups with and without coronary artery disease were similar. There was no significant difference in the prevalence of thyroid antibodies in patients with or without coronary artery disease.

Hypothyroidism associated with positive results of the perchlorate discharge test in elderly patients

In 172 patients over the age of 55, determinations were made of thyrotropin concentrations in plasma. Although they showed such symptoms or signs of hypothyroidism as puffy face, dry skin, general malaise, cold intolerance, or constipation, there were no clinical indications of overt hypothyroidism. All the patients were apparently in a normal nutritional state, without any specific medication that might cause thyroid abnormalities. Seventeen (six men and 11 women, 9.9 percent) of the 172 patients, aged 58 to 83, had elevated plasma thyrotropin levels, ranging from 12.1 microU/ml to 170 microU/nl. To investigate the characteristics of hypothyroidism in the elderly, the perchlorate discharge test was performed in these patients. In 15 of the 17 patients, 123I thyroid uptake diminished markedly immediately after the administration of 1 g perchlorate. Thirteen of these 15 patients showed markedly diminished thyroxine (T4) levels in serum, whereas the magnitude of diminution in serum 3,5,3'-triiodothyronine (T3) values was small. Two patients with the negative discharge results showed normal T4 and T3 levels in serum. Four patients had a very small goiter, and the remaining 13 patients had no detectable goiter. Fifteen of the 17 patients had no detectable circulating thyroid antibodies in repeated determinations, and the histologic features of Hashimoto's thyroiditis were not found in the thyroid specimens obtained from two patients. These findings suggest the existence of hypothyroidism attributable to iodine organification defect without evidence of autoimmune thyroiditis in some cases in elderly patients.

"Symptomless" autoimmune thyroiditis in depression

The magnitude of the thyroid-stimulating hormone (TSH) response induced by thyrotropin-releasing hormone (TRH) helps identify patients whose thyroid is failing. Many of these patients have been found to have Hashimoto's thyroiditis, symptomless autoimmune thyroiditis (SAT), and subclinical hypothyroidism. While patients with SAT are clinically euthyroid, what might be "symptomless" for the endocrinologist might be a syndrome presenting with psychiatric symptoms to the psychiatrist. As a preliminary test of this hypothesis, we tested 100 consecutive admissions to a psychiatric hospital who complained of depression or lack of energy. Fifteen (15%) of 100 patients were identified from the baseline thyroxin (T4), triiodothyronine (T3) resin uptake (RU), T3 radioimmunoassay (T3RIA), TSH, and TRH test who met criteria for either subclinical, mild, or overt hypothyroidism. Of these 15 patients, 9 (60%) had positive thyroid microsomal antibodies with titers of greater than or equal to 1:10. Our data suggest that SAT is not symptomless and may be an important diagnosis to consider in the evaluation of depressed, anergic, or atypical patients.

Autoimmune lymphocytic thyroiditis in dogs

Primary diseases of the thyroid gland, especially lymphocytic thyroiditis and idiopathic follicular atrophy, were the most common lesions associated with clinical hypothyroidism in pet dogs. Lymphocytic thyroiditis resembled naturally occurring lymphocytic thyroiditis in the Obese-strain of White Leghorn chickens and Hashimoto's thyroiditis in man. The morphology of the thyroid lesion and frequent occurrence of circulating thyroglobulin autoantibodies suggested that lymphocytic thyroiditis was immune-mediated in pet dogs. Thyroid lesions similar to naturally occurring autoimmune thyroiditis in experimental dogs were induced by a local thyroidal graft-versus-host reaction. The lesions observed in the thyroid lobe which was not injected with immunocompetent cells appeared to develop from the formation of thyroid antibodies in the gland by migrating host lymphocytes. Autoimmune lymphocytic thyroiditis occurred secondary to an unrelated immune response occurring in target tissue.

Primary biliary cirrhosis--a revised clinical spectrum

The presentation or method of detection of 93 patients with primary biliary cirrhosis (PBC) from Northern England is reported. Almost half (45/93) the patients had no symptoms of liver disease when PBC was diagnosed; in many of them serum antimitochondrial activity (AMA) was detected during immunological screening for other diseases. 13 patients with normal liver function tests had symptomless PBC. Liver histology in 6 of these was diagnostic for PBC, and 7 had histology suggestive of PBC; all had a positive AMA titre greater than or equal to 1/40. The mortality of the symptom-free AMA-positive patients over a mean follow-up of 4-5 years did not differ from that of the general population. Only 1 out of 45 initially symptom-free patients died in the follow-up period (8 months-12 years). 37 patients had disorders which may be associated with PBC--including 16 with thyroid disease, 9 with rheumatoid arthritis, and 5 with mixed connective tissue disease. It is suggest that, as with autoimmune thyroid disease, overt organ damage never develops in many patients with symptomless PBC.

Histologic and ultrastructural evaluation of thyroid lesions associated with hypothyroidism in dogs

Thyroid lesions in 16 pet dogs with hypothyroidism were evaluated by light and electron microscopy. Lymphocytic thyroiditis, found in seven dogs, was characterized by diffuse infiltration of the thyroid gland by lymphocytes, plasma cells and macrophages with formation of some lymphoid nodules and destruction of follicles, progressing to replacement of most of the thyroid by fibrous connective tissue. The basement membrane around follicles was thick and had electron-dense deposits. The morphology of the thyroid lesions and the presence of circulating thyroglobulin autoantibodies suggested that lymphocytic thyroiditis was immune-mediated. Idiopathic follicular atrophy, found in nine dogs, was characterized by loss of thyroid parenchyma and replacement by adipose connective tissue. Degeneration of individual follicular cells was present in the early stage, with exfoliation into the colloid and interfollicular area. Most of the thyroid gland consisted of adipose connective tissue with either interspersed small follicles or individual follicular cells that had dilated rough endoplasmic reticulum, large Golgi apparatus, and intracytoplasmic microfollicles in the advanced stage. Follicular atrophy was a degenerative lesion of follicular cells of unknown cause, not associated with inflammatory destruction in the thyroid gland.

Natural history of autoimmune thyroiditis

One hundred and sixty-three asymptomatic people with thyroid antibodies or raised serum thyrotrophin (TSH) concentrations, or both, and 209 age-matched and sex-matched controls without either marker of thyroid disorder were followed up for four years to determine the natural history of autoimmune thyroiditis. Mildly raised TSH concentrations alone and the presence of thyroid antibodies alone did not significantly increase the risk of developing overt hypothyroidism during the four years compared with the controls. Overt hypothyroidism developed at the rate of 5% a year in women who initially had both raised TSH concentrations and thyroid antibodies. Prophylactic treatment with thyroxine may be justified in women found to have both markers of impending thyroid failure. The cost effectiveness of screening the adult population remains to be evaluated.

Thyroid autoantibodies in an Australian community

Little data are available concerning the prevalence of thyroid autoantibodies in the Australian community. The present study, performed in a non-iodine deficient area, reveals a high prevalence of microsomal and thyroglobulin autoantibodies in healthy females. The proportion of females with one or either antibody is almost three times greater than that observed for males, but, in both sexes, the prevalence does increase with age.

The cardiovascular and lipid status of pernicious anaemia patients with and without thyroid antibodies

A study has been undertaken of the cardiovascular and lipid status of patients with pernicious anaemia (PA). There was no evidence of elevated cholesterol, triglyceride and lipoprotein concentrations nor of an increased prevalence of ischaemic heart disease and peripheral vascular disease in those patients who had positive thyroid antibodies compared with those who had not. There were also no significant differences in cardiovascular or lipid status in the antibody positive patients between those who had an exaggerated thyroid stimulating hormone (TSH) response to thyrotrophin releasing hormone (TRH) and those who had a normal or impaired response. It is suggested that an exaggerated response to TRH in these PA patients usually indicates 'compensated euthyroidism' and not 'subclinical hypothyroidism' or 'premyxoedema' and that they are no more at risk for cardiovascular disease than are PA patients with no evidence of thyroid abnormality.

Thyroid function and antibody studies in pernicious anaemia

Thyroid antibodies were demonstrated in 57% of thirty pernicious anaemia patients without overt thyroid disease. Elevated basal thyroid stimulating hormone (TSH) levels and an enhaced TSH response to thyrotrophin releasing hormone (TRH) only occurred in thyroid antibody positive subjects; by contrast the thyroid antibody negative subjects in the older age group frequently and undetecable basal TSH levels and an impaired TRH response. Thyroid hormone concentrations provided no absolute evidence of hypothyroidism in any of the patients.

Thyroid and other autoantibodies in British and Japanese women: an epidemiological study of breast cancer

To define the role of asymptomatic autoimmune thyroiditis in the cause of breast cancer, the presence of circulating thyroid autoantibodies was studied in two populations, one with a high risk of breast cancer (British women) and one with a low risk (Japanese women). Ostensibly healthy women and patients with breast cancer from both countries were studied. There was no difference in the incidence of thyroid autoantibodies between women with breast cancer and healthy women in either race. The incidence of thyroid autoantibodies in healthy British women, however, was two to three times that in healthy Japanese women. The incidence of reticulin antibodies, was considerably higher in both groups of Japanese women. No remarkable differences in the incidence of antinuclear, smooth-muscle, antimitochondrial, gastric parietal cell, or liver-kidney microsomal antibodies were found between women with breast cancer and healthy women or between the two races. Only the incidence of antinuclear antibodies was marginally higher in Japanese patients with advanced cancer. These results indicate that asymptomatic autoimmune thyroid disease is more prevalent among British than among Japanese women, but they fail to provide direct evidence that autoimmune thyroid disease is associated with breast cancer. Prospective studies of women with autoimmune thyroiditis and studies of young women from low-risk and high-risk populations are needed.

Natural course of symptomless autoimmune thyroiditis

Out of 18 subjects with symptomless autoimmune thyroiditis (S.A.T.) 5 (28%) became hypothyroid within 4 to 39 months of observation, whereas 13 (72%) remained euthyroid up to atleast 28 to 50 months. In all those who developed hypothyroidism the basal serum level of thyroid-stimulating hormone (T.S.H.) was already initially above normal (normal range 1-6--6-9 muU/ml) and 4 had markedly elevated concentrations (less than 19 muU/ml). All those subjects developing hypothyroidism also had initially an exaggerated response to thyrotropin-releasing hormone (T.R.H.) (upper normal limit, delta T.S.H. 30 muU/ml), and in 4 the response was much exaggerated (delta T.S.H. less than 70 muU/ml). In 3 of these subjects the basal T.S.H. and the response to T.R.H. were reassessed before starting the substitution therapy and in all there was a further increase in both values. The basal serum T.S.H. was initially also slightly increased in 2 and the response to T.R.H. slightly above normal in 4 subjects who remained euthyroid. The basal T.S.H. level became normal in both cases with elevated values; and the response to T.R.H. declined to a normal level in 3 of the latter 4 subjects, but showed a further increase in 1. The thyroglobulin antibody (TgA) titres were initially significantly elevated in 15 subjects and the thyroid microsomal antibodies (MsA) in 1. The TgA titres decreased during the observation period in all but 1 subject and a similar trend was observed as regards the MsA titres. It is concluded that within a few years of observation a substantial number of subjects with S.A.T. will be hypothyroid. A definitively increased basal serum T.S.H. level and a markedly exaggerated response to T.R.H. in the symptomless stage of the disease is connected with a high risk of late hypothyroidism.

Serum thyroxine in the early diagnosis of carbon disulfide poisoning

Serum thyroxine and blood lipids were assayed in 45 subjects exposed to carbon disulfide (CS2). A highly significant statistical reduction of thyroxine in relation to the exposure time was found and the levels appeared lower in the subjects with retinal vessel alterations. A significant interrelation between cholesterol and serum thyroxine was also evidenced. Serum thyroxine assay is suggested as a reliable test in the early diagnosis of CS2 poisoning.

Grades of hypothyroidism

Seventy-nine patients with hypothyroidism and autoimmune thyroid disease were studied, and allotted to one of four categories on the basis of clinical and biochemical features. Firstly, patients with overt hypothyroidism had obvious clinical features of hypothyroidism and abnormal results from routine tests of thyroid function. Secondly, those with mild hypothyroidism, however, had minor and non-specific symptoms, but the routine measurements of circulating thyroid hormone concentration generally lay within the normal range, although they were significantly lower than those seen in subclinical hypothyroidism or in normal subjects. The serum concentration of thyroid-stimulating hormone (TSH) was raised in this group and their symptoms resolve with treatment. Thirdly, patients with subclinical hypothyroidism were asymptomatic, had a raised serum TSH concentration, but all other measurements of thyroid function are indistinguishable from those recorded in people with autoimmune thyroid disease without disturbance of thyroid function and in normal subjects. Lastly, subjects with circulating thyroid antibodies, normal indices of thyroid function, and a normal serum TSH concentration were indistinguishable biochemically from normal subjects.Thus hypothyroidism is a graded phenomenon, the most valuable features for defining the individual grade being the clinical manifestations, the serum TSH concentration, and the presence of circulating antibodies to thyroid tissue.

Grades of hypothyroidism

Seventy-nine patients with hypothyroidism and autoimmune thyroid disease were studied, and allotted to one of four categories on the basis of clinical and biochemical features. Firstly, patients with overt hypothyroidism had obvious clinical features of hypothyroidism and abnormal results from routine tests of thyroid function. Secondly, those with mild hypothyroidism, however, had minor and non-specific symptoms, but the routine measurements of circulating thyroid hormone concentration generally lay within the normal range, although they were significantly lower than those seen in subclinical hypothyroidism or in normal subjects. The serum concentration of thyroid-stimulating hormone (TSH) was raised in this group and their symptoms resolve with treatment. Thirdly, patients with subclinical hypothyroidism were asymptomatic, had a raised serum TSH concentration, but all other measurements of thyroid function are indistinguishable from those recorded in people with autoimmune thyroid disease without disturbance of thyroid function and in normal subjects. Lastly, subjects with circulating thyroid antibodies, normal indices of thyroid function, and a normal serum TSH concentration were indistinguishable biochemically from normal subjects.Thus hypothyroidism is a graded phenomenon, the most valuable features for defining the individual grade being the clinical manifestations, the serum TSH concentration, and the presence of circulating antibodies to thyroid tissue.