Graves' disease and thyroxine-binding globulin deficiency

Thyroxine-binding globulin (TBG) deficiency has been frequently described in single patients and in many families. Most people with abnormal TBG concentrations are euthyroid. Cases of Graves' disease and TBG deficit have rarely been reported. We describe the case of a person with Graves' disease and TBG deficiency. Because of this condition, the patient had a misdiagnosis during part of his clinical history, and therefore underwent unnecessary therapy.

Diagnosis of amiodarone-iodine-induced thyrotoxicosis(AIIT) associated with severe nonthyroidal illness

A rare case of amiodarone-iodine-induced thyrotoxicosis (AIIT) associated with nonthyroidal illness is reported. Serum total thyroxine (TT4) and free T4 (FT4) concentrations were elevated and serum TSH was undetectable as frequently observed also in euthyroid amiodarone-treated patients. At variance with common forms of AIIT, serum total triiodothyronine (TT3) was reduced due to low-T3 syndrome. The laboratory diagnosis was made on the basis of elevated free T3 (FT3) levels. Thus, in patients with severe nonthyroidal illness submitted to chronic amiodarone treatment, thyroid status can only be determined by free hormone measurement, particularly FT3 in the case of thyrotoxicosis.

Adverse cardiovascular responses to thyrotropin-releasing hormone (200 micrograms) in cardiac patients

Although a pressor effect of 500 micrograms i.v. thyrotropin-releasing hormone (TRH) in noncardiac patients has been reported, the effect of a lesser dose of TRH (200 micrograms) in cardiac patients has not been evaluated. We performed a 200 micrograms i.v. TRH test to exclude thyrotoxicosis in 20 cardiac patients, aged 38 to 42 years. No clinical side effects were noted, but increments in systolic and diastolic blood pressure of 21.8 +/- 2.7 and 17.3 +/- 1.6 mm Hg (SE), respectively, were documented. Mean arterial pressure rose from 104.9 +/- 2.9 to 123.7 +/- 5.5 mm Hg (SE) after TRH (P less than 0.001). In nine patients the pressor response persisted for 5 to 20 min, and blood pressures of 220 mm Hg systolic and 145 mm Hg diastolic were recorded. We conclude that the 200 micrograms TRH i.v. has a significant pressor effect.

Immunoradiometric assay of serum thyroid stimulating hormone (TSH) as a first-line test in a mixed hospital population

An immunoradiometric assay of thyroid stimulating hormone (TSH-IRMA) was evaluated as a first-line test for the diagnosis of thyroid disease in a prospective study of 318 consecutive patients in a major city hospital. The results of TSH-IRMA were compared with the diagnoses made by means of our usual diagnostic methods. Based on previous studies a serum TSH level of 0.15 mU/l was chosen as cutoff limit for calculation of diagnostic performance. For patients with serum TSH greater than 5.0 mU/l the results of TSH-IRMA were in accordance with the results of our routine radioimmunoassay. Patients with serum TSH levels between 0.15 mU/l and 5.0 mU/l were euthyroid (the diagnostic sensitivity was 100%). Consequently, the final diagnosis could be made with one test and within two days for 88% of patients. Patients with serum TSH less than 0.15 mU/l needed supplementary tests since only 32% of these patients had thyrotoxicosis, 32% had a non-toxic goiter, and 36% had no thyroid disease.

Euthyroid hyperthyroxinemia and inappropriate secretion of thyrotropin. Recognition and diagnosis

Various disease states associated with euthyroid hyperthyroxinemia and inappropriate thyrotropin secretion are becoming increasingly recognized. These diagnoses were established in six (11%) of 57 patients referred for evaluation of elevated free thyroxine index over an 11-month period. Failure to separate these entities from primary thyrotoxicosis may result in unnecessary thyroid ablative therapy and subsequent clinical confusion. Several illustrative patient summaries are presented to outline an approach to this clinical challenge.

Myocardial infarction in Graves' disease without coronary artery disease

A 45-year-old female without coronary risk factors showed a 20 kg decrease in body weight, hyperhydrosis, palpitations and dyspnea on exertion for 2 months, and nocturnal dyspnea for 1 month before admission. She did not notice chest pain indicative myocardial infarction or fever suggestive myocarditis. Graves' disease was confirmed by exophthalmos and elevated titers of T3 and T4 thyroid hormones. Cardiac catheterization studies demonstrated no significant coronary artery disease but showed akinesis of the anteroseptal and apical walls which suggested myocardial infarction. Thyroid hormone may directly influence myocardial oxygen supply and demand and, by some unknown mechanism, cause a critical imbalance in coronary circulation resulting in myocardial infarction.

The occurrence of organic disease of possible or probable aetiological significance in a population of 268 cases of first episode schizophrenia

In a sample of 268 cases of first-episode schizophrenia, 15 patients were found to have organic disease which appeared relevant to the mental state. There were three cases of syphilis, two cases of sarcoidosis, three of alcohol excess and two of drug abuse. There was one case each of carcinoma of the lung, autoimmune multisystem disease, cerebral cysticercosis, thyroid disease and previous head injury. In this series, identified organic disease was associated with less than 6% of cases of schizophrenia.

Abnormalities in pituitary thyroid axis function tests in patients with paroxysmal supraventricular arrhythmias

The study was carried out on 60 consecutive patients (23 males and 37 females) aged between 20 and 83 years (means +/- SD, 40.7 +/- 16) who arrived at our Cardiologic Unit with paroxysmal supraventricular arrhythmias (PSVA) including junctional paroxysmal tachycardia (n = 32), atrial fibrillation (n = 13), atrial flutter (n = 1), premature beats (n = 13) and with no obvious cardiovascular causes. Serum thyroxine and triiodothyronine were normal in all patients and thyroid scintiscan revealed normal shape and size thyroids without autonomously functioning nodule(s). Thyrotropin (TSH) response to thyrotropin releasing hormone (TRH) was normal in 44 subjects in whom normal serum free T4 (FT4) and free T3 (FT3) levels were measured. Six patients with normal FT4 and FT3 levels did not respond to TRH. Abnormalities in thyrotropin response to TRH were observed in 10 patients all exhibiting increased FT4 or also FT3 levels. Among these, 5 patients did not respond to TRH, whereas the remaining 5 exhibited a blunted TSH response to TRH. These results suggest that only in a small proportion (5/60) of consecutive patients with PSVA it is possible to recognize a status of "occult thyrotoxicosis" on the basis of the combined evaluation of free thyroid hormones and TSH response to TRH.

Amiodarone: a common source of iodine-induced thyrotoxicosis

Amiodarone, a iodine-rich drug widely used in the treatment of tachyarrhythmias, represents one of the most common sources of iodine-induced thyrotoxicosis. The data concerning 58 patients with amiodarone-iodine-induced thyrotoxicosis (AIIT) were analyzed in the present study. Prevalence of AIIT was higher in males than in females (M/F = 1.23/l). Thyrotoxicosis occurred either during treatment with or at various intervals after withdrawal of amiodarone. AIIT developed not only in patients with underlying thyroid disorders, but also in subjects with apparently normal thyroid gland. Classical symptoms of thyrotoxicosis were often lacking, the main clinical feature being a worsening of cardiac disorders. Biochemical diagnosis of AIIT was established by the finding of elevated serum total and free triiodothyronine levels, since elevated serum total and free thyroxine could be found also in euthyroid amiodarone-treated subjects. Twenty-four-hour thyroid radioiodine uptake was very low or undetectable in AIIT patients with apparently normal thyroid glands, while it was inappropriately elevated in patients with underlying thyroid disorders, despite iodine contamination. The role of autoimmune phenomena in the pathogenesis of AIIT appeared to be limited, because circulating thyroid autoantibodies were undetectable in AIIT patients without underlying thyroid disorders or with nodular goiter. Conversely, humoral features of thyroid autoimmunity were mostly found in AIIT patients with diffuse goiter. Treatment of AIIT appeared to be a difficult challenge. Among the 11 patients given no treatment, thyrotoxicosis spontaneously subsided in the 5 patients with apparently normal thyroid gland, whereas the 6 patients with nodular or diffuse goiter were still hyperthyroid 6-9 months after discontinuation of the drug. The administration of high doses (40 mg/day) of methimazole alone proved to be ineffective in most (14/16) patients given this treatment. Twenty-seven patients were treated by methimazole combined with potassium perchlorate (1 g/day). With one exception, euthyroidism was restored within 15-90 days in all cases with underlying thyroid abnormalities, and within 6-55 days in subjects with apparently normal thyroid gland. Thus, the combined treatment appears to be the most effective one, but, due to the potential toxicity of potassium perchlorate, it should be reserved to patients with severe thyrotoxicosis and should be carefully monitored.

Artefactual increase in serum thyrotropin concentration caused by heterophilic antibodies with specificity for IgG of the family Bovidea

A 19-year-old white woman presented with symptoms compatible with mild hyperthyroidism and biochemical evidence suggestive of autonomous thyrotropin (TSH) secretion. Intensive investigation of the pituitary-thyroid axis suggested that the basal concentrations of TSH were artefactually increased owing to heterophilic antibodies in the patient's serum with a broad specificity for immunoglobulin class G of the family Bovidea. These heterophilic antibodies complexed with the ovine antisera to human thyrotropin that are used in the RIA system, in particular blocking the binding of TSH but also partly blocking interaction with the second antibody. When TSH was measured immunometrically or by an RIA with TSH-specific antisera of rabbit origin, the concentrations measured were within the appropriate reference intervals. The blocking effect can be overcome by including large quantities of non-TSH-specific ovine IgG in assay incubation mixtures. Interference of this type is generally not appreciated and its incidence is poorly characterized, but it may have implications for any method in which antibodies are used as reagents.

Prediction of relapse in Graves' disease

In order to predict remission in Graves' disease, it is important to recognize abnormalities of thyroid function in euthyroid subjects who are prone to be thyrotoxic as well as in those who are untreated thyrotoxic patients. Changes in thyroid function during thionamide therapy and in remission are also very important to understand the remission and the relapse in Graves' disease. From the careful analysis of thyroid-related abnormalities in each stage of the clinical course of Graves' disease, it is suggested that to bring patients into remission by thionamide therapy is merely to return them to a thyroid functional status prior to the development of clinical active Graves' disease. Various methods employed to predict remission are useful in differentiating active patients from those in remission but none of them can predict the duration of remission.

Thyrotoxicosis in the very old

The records of 25 patients older than 75 years of age with the diagnosis of hyperthyroidism were reviewed. The mean age of the group (22 women and three men) was 81.5 years, the eldest being 95 years old. Twenty-one patients had Graves' disease, three had multinodular goiter, and one had toxic adenoma. Major presenting symptoms included weight loss (44 percent), palpitations (36 percent), and weakness (32 percent). The average number of thyrotoxic symptoms was only two per patient. Two patients were asymptomatic. Clinical signs included fine skin (40 percent), tremor (36 percent), atrial fibrillation (32 percent), and tachycardia (28 percent). The thyroid was palpable in only three patients with Graves' disease. Mean blood thyroxine level was 15.6 micrograms/dl (range, 11.5 to 24); blood triiodothyronine level was elevated in only half of the patients. One patient had triiodothyronine toxicosis. Mean 24-hour radioiodine uptake was 52 percent. Five patients had normal uptake. No correlation could be established between age, clinical symptoms, signs, and hormone blood levels. Because signs and symptoms of hyperthyroidism in the very old may be too subtle for clinical diagnosis, all elderly subjects should have periodic screening of blood thyroxine levels.

Admission thyroid function testing in elderly patients

The free thyroxine index (FTI) was measured in 307 elderly patients admitted to two geriatric units. The initial FTI was abnormal in 41 (13.3%), being raised in 27 and low in 14 patients. On further testing, these abnormalities were found to be either transient or of no clinical significance in 36 of the 41 patients (88%). Only five of the 307 patients (1.6%) were finally treated for previously undiagnosed thyroid disease and of these three improved (1%). Thyroid disease identified by routine screening, and not suspected from the history and clinical findings, was present in only two patients (0.7%). In view of these findings we suggest that thyroid screening is no more justified in the elderly than in younger hospitalised patients.