Aetiology of hypothyroidism

Thyroid disease and high concentration of serum thyrotrophin in a population sample of women. A 4-year follow-up

In a population study in Göteborg, Sweden, comprising women in the age strata 44, 52, 56, 60 and 66 years, serum thyrotrophin (S-TSH) was determined in 283 women representative of the general population of women of these ages. No women with previously unknown hypothyroidism were found at the clinical examination; 47 (3.7%) were on thyroxine treatment, 9 (0.7%) because of spontaneous hypothyroidism. Sixteen women (1.2%) had markedly elevated S-TSH concentration (less than 14 mU/l). They were studied further by determination of thyroid hormones and circulating antithyroid microsomal and thyroglobulin antibodies, and those with goiter were subjected to fine-needle biopsy of the thyroid gland. They were furthermore followed for four years. Four euthyroid women were given thyroxine because of goiter and abnormal laboratory test results. Of nine individuals with high S-TSH concentration as well as high titers of thyroid antibodies and/or biopsy evidence of autoimmune thyroiditis, seven became hypothyroid within the four years of follow-up. The other two women had consistently elevated basal S-TSH concentration and exaggerated S-TSH response after thyroliberin administration. We conclude that the majority of individuals without previously recognized thyroid disease who have S-TSH concentration above 14 mU/l with the assay used will require thyroxine therapy within a few years. In one woman, however, with multinodular colloid goiter and high titer of antimicrosomal antibodies, the basal S-TSH concentration decreased during follow-up to a high normal value; the S-TSH response to thyroliberin was high borderline. She remained euthyroid during follow-up. The results suggest an annual incidence of spontaneous hypothyroidism of 1-2 cases per 1000 middle-aged females in Swedish west-coast population.

Primary idiopathic hypothalamic hypothyroidism. Report of four cases

One man and three women with hypothalamic hypothyroidism are described; they had isolated thyrotropin-releasing hormone deficiency, otherwise normal pituitary function, and no identifiable central nervous system anatomic abnormality. Serum thyrotropin levels were low and thyrotropic response to thyrotropin-releasing hormone was uniformly present, consistent with a hypothalamic cause of hypothyroidism. In two patients, hypothyroidism was transient and spontaneously resolved; in one of them, it was recurrent. Because hypothalamic hypothyroidism is mild and potentially reversible, it is suggested that such patients have follow-up evaluation before therapy is initiated in order to avoid unnecessary treatment.

Use of a single thyroxine test to evaluate ambulatory medical patients for suspected hypothyroidism

Previous recommendations for the use of thyroid function tests to diagnose patients with possible hypothyroidism have discounted the value of a total thyroxine (T4) test because many clinically hypothyroid patients have T4 levels that fall within the "normal" range. The authors examined the predictive value of a total T4 measurement in the evaluation of ambulatory general medical patients suspected of having hypothyroidism. Pregnant patients and those who were taking medications that interfere with thyroid homeostasis were excluded. Simultaneous T4 and thyrotropin (TSH) tests of 93 consecutive outpatients suspected to have hypothyroidism but found to be euthyroid and 27 patients discovered to be hypothyroid (TSH greater than 10 microU/ml) were examined. A T4 of 7.0 microliter/dl or less had a sensitivity of 93% with a false-positive rate of 19%. A T4 greater than 8.0 microgram/dl appeared to exclude hypothyroidism (negative posttest probability of 100%). It may be possible to achieve cost savings without loss of diagnostic accuracy by using a single total T4 measurement for the initial evaluation of suspected hypothyroidism in selected outpatients.

Myxoedema followed by TSAb-induced hyperthyroidism: report of 2 cases

The development of spontaneous hyperthyroidism following primary hypothyroidism is an unusual occurrence. We report two cases of confirmed primary hypothyroidism who subsequently became hyperthyroid. Thyroid stimulating antibodies were present in the sera of both patients during the hyperthyroid state. The significance of this sequence of events is discussed and a possible explanation proposed.

When does rheumatoid disease start?

Stored serum specimens collected in connection with a community-oriented epidemiologic study were available from 30 subjects who later developed seropositive rheumatoid arthritis. In 9 of these pre-rheumatoid specimens, the Rose-Waaler test result was positive, and in 16, the latex fixation test was positive. Two-thirds of the samples were positive when the interval between taking the blood specimen and onset of the disease was less than 4 years, and one-third were positive when the interval was greater than or equal to 4 years. The occurrence of rheumatoid factor preceded the onset of clinical disease more often in males than in females.

Development of adrenocortical failure in non-Addisonian patients with antibodies to adrenal cortex. A clinical follow-up study

Out of 1036 sera tested for the presence of antibodies to adrenal cortex using the indirect immunofluorescence (IFL) method, fifteen out of 323 patients with Graves' thyrotoxicosis, 6/105 Hashimoto's thyroiditis, 3/29 myxoedema, 2/49 asymptomatic autoimmune thyroiditis, 1/12 subacute thyroiditis, and 4/130 with myasthenia gravis were positive. Thirty antibody-positive non-addisonian patients were tested for subclinical adrenocortical failure and followed up over a period of 1-3.5 years. Three women with Graves' disease had biochemical signs of early Addison's disease at the first Synacthen test. Two young women with controlled Graves' thyrotoxicosis developed a diminished adrenocortical reserve within 2 and 3 years, respectively; one of them developed anovulatory cycles which did not respond to clomiphene treatment. Both patients had high titres of complement-fixing adrenal antibodies before the adrenal failure could be recognized by functional tests. One elderly female patient in whom a euthyroid goitre with adrenal and thyroid antibodies was detected in 1977, developed Graves' thyrotoxicosis in 1980. These observations indicate that antibodies to adrenal cortex have a high clinical significance and may allow the early diagnosis of Addison's disease even in the absence of specific clinical symptoms.

Thyroid growth-blocking antibodies in primary myxoedema

Adult primary myxoedema is usually due to an autoimmune thryoiditis characterized by progressive shrinking of the thyroid gland, loss of epithelium, dense infiltration by sensitized lymphocytes and plasma cells with final replacement of the gland by a fibrous scar. Antibodies directed against thyroglobulin (TgHA) and microsomal antibodies (McHA), detectable years before the onset of hormonal failure, and cell-mediated immune mechanisms contribute to the pathogenesis. When 90% of the gland is destroyed, the secretion of thyroid hormones (T3/T4) falls below normal needs and pituitary thyrotrophs react by producing over 100 times the normal amount of thyroid-stimulating hormone (TSH) which should normally lead to regrowth of the gland as happens in goitrous Hashimoto thyroiditis. The inability of the thyroid in primary myxoedema to respond to the trophic action of TSH suggested that blocking antibodies exist in this disease which compete with TSH for its receptors. The trophic effect of TSH can be assayed in vitro by measuring DNA-synthesis by Feulgen cytophotometry; elevated pentose-shunt oxidative activity correlates with DNA synthesis. Here we report that immunoglobulins from patients with adult, primary myxoedema block the trophic effect of TSH, as assessed by this in vitro system. This is in marked contrast to the growth stimulation induced by immunoglobulins from patients with thyrotoxic Graves' disease with prominent goitres.