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The Diagnosis of Thyrotoxicosis WILLIAM R. GREIG

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The Diagnosis of Thyrotoxicosis WILLIAM R. GREIG Postgrad Med J: first published as 10.1136/pgmj.49.573.469 on 1 July 1973. Downloaded from Postgraduate Medical Journal (July 1973) 49, 469-476. The diagnosis of thyrotoxicosis WILLIAM R. GREIG IAIN R. MCDOUGALL M.D., Ph.D., F.R.C.P. M.B., Ph.D., M.R.C.P. HENRY W. GRAY M.B., M.R.C.P. University Department of Medicine and Nuclear Medicine and Thyroid Clinics, Royal Infirmary, Glasgow Summary intrinsically overactive discrete adenoma in the Thyrotoxicosis is a clinical syndrome due to excessive thyroid, as distinct from a toxic multinodular goitre amounts of thyroid hormone in the circulation and (see below). Rarely, thyrotoxicosis is the result of tissues. Graves' disease, goitre and exophthalmos, is metastatic untreated follicular carcinoma, and over- the commonest variety, but in some parts of the world treatment of hypothyroidism may cause some of the thyrotoxicosis supervenes on the background of a long clinical features. Very occasionally thyrotoxicosis is standing nodular goitre. Other varieties such as ectopic seen in patients with trophoblastic tumours or other TSH syndromes are very rare. visceral tumours, and this is usually attributed to the The diagnostic sequence in practice starts with artificial production of thyroid stimulating hormone clinical suspicion and a decision can often be made on (TSH) or TSH-like substances by the deranged by copyright. the symptoms and signs alone. It is, however, always tumour cells (ectopic TSH syndromes). Sometimes advisable to confirm the presence or absence of thyro- patients with active acromegaly are also thyrotoxic, toxicosis. There has been re-orientation in the simple but this does not seem to be due to excess TSH test procedure used in this respect. Measurements such stimulation; other rare types of thyrotoxicosis as serum TSH and serum TSH response to TRH and probably include some people whose hypothalamus measurements of serum LATS levels are available is unresponsive to a high normal blood thyroid only in a few centres and are not discussed in detail. hormone level and they proceed to secrete an in- Tests based on the carriage of thyroid hormones in appropriate amount of TSH-releasing hormone the blood are preferable to in vivo radionuclide studies, (TRH) and consequently the blood TSH is raised, http://pmj.bmj.com/ particularly when the patient is thought to be euthyroid. leading to thyrotoxicosis. We advise a serum PB1271 and serum total thyroxine The very great majority ofthyrotoxic patients have, estimation in all patients. If the data are abnormal we however, either toxic goitre with exophthalmos add a serum T3 resin estimation to check whether the (Graves' disease) or toxic multinodular goitre with- values are due, for example, to iodine contamination or out exophthalmos. In Western Europe and the altered binding. U.S.A., for example, Graves' disease is much more but We advise radionuclide studies in all doubtful cases common than toxic multinodular goitre, the on September 28, 2021 by guest. Protected and measurements such as the 4 hr or 24 hr 1311 uptake latter is not rare in older patients; there is usually a and the 48 hr serum PB1311 are very helpful. A thyroid history of long-standing goitre and recent thyro- uptake suppression test may be required if there is still toxicosis. Toxic multinodular goitre is more com- doubt. In general thosepatients goingfor thyroidectomy monly seen in countries such as Norway and or 1311 therapy should have a scan performed. With Tasmania with epidemiological but moderate iodine improved technology much safer radionuclides, such deficiency, and there is evidence that when this has as 1231 or 99mTc, may be usable when thyrotoxicosis is been corrected the prevalence of thyrotoxicosis suspected in children or during pregnancy. increases; presumably the iodine deficiency curtails the potentially thyrotoxic thyroid. Causation The fundamental cause of Graves' disease is not Thyrotoxicosis is a common clinical disorder and known but it seems that the primary disorder lies a consequence of too much thyroxine (tetraiodo- outside the thyroid. Certainly it is not due to too thyronine-T4) and/or triiodothyronine (T3) in much pituitary TSH (in fact TSH is not detectable circulation and tissues. There are a number of rare in the blood of people with active Graves' disease causes; exceptionally it arises because there is a true and the pituitary responds poorly to TSH-releasing Postgrad Med J: first published as 10.1136/pgmj.49.573.469 on 1 July 1973. Downloaded from 470 W. R. Greig, I. R. McDougall and H. W. Gray hormone-TRH). The syndrome of Graves' disease orientate the busy doctor in this respect. Emphasis also has extrathyroidal tissue abnormalities; the will, of course, be put on simple tests and those using exophthalmos and periorbital swelling are almost radionuclides, but it is hoped this will be done in the invariable, but sometimes there is in addition pre- context of the general diagnostic process. tibial myxoedema, finger clubbing and acropachy. In young people there may be slight enlargement of Clinical diagnosis neck lymph nodes, a just palpable spleen and, if Nobody would disagree that the most important special X-rays are carried out, the thymus may be first step in making a diagnosis of thyrotoxicosis is seen to be enlarged too. Some insight into those to suspect it. Obviously a previous or family history apparently linked observations has been given by is helpful and the presence of eye signs and a goitre the discovery of an unusual 7S IgG immunoglobulin have high diagnostic value too. The clinical index in the neat sera of 50 %, or the concentrated sera of (Table 1) described by Crooks, Murray & Wayne 80%, of patients with active Graves' disease. This (1959) is very helpful to the general physician, in substance, when tested in appropriately prepared that patients can be segregated into three general mice or guinea pigs causes prolonged thyroid stimula- categories on the basis of the symptoms and signs. tion (long acting thyroid stimulator-LATS). Its There will be those who appear to be definitely not prevalence and titres are high in those patients with thyrotoxic (total diagnostic score less than 11), those extrathyroidal tissue manifestations of Graves' who appear to be unequivocally thyrotoxic (total disease and the peripheral lymphocytes from the diagnostic score greater than 19) and those in whom same patients can be induced to synthesise LATS in the diagnosis is doubtful (total diagnostic score vivo. There is, however, a generally poor correlation between 11 and 19). Patients who have a history of between blood LATS titres and the severity of thyro- treated thyrotoxicosis are a special group where the toxicosis, the degree of exophthalmos and the res- index is not applicable, since some signs such as ponse to therapy whether by antithyroid drugs, goitre and exophthalmos are residual even when the operation or radioiodine. Nevertheless, the discovery patient is in remission. This index is also not applic- of LATS should open new avenues of thought and able to those patients with unusual forms of thyro-by copyright. research. Included in the general problem area is the toxicosis, such as ectopic TSH syndrome. These need to explain the inheritance of the tendency to rarer forms of thyrotoxicosis will not be further dis- develop the condition, its association with common cussed. Thyrotoxicosis in the newborn and in preg- conditions such as pernicious anaemia and rheuma- nancy pose special diagnostic problems and thyro- toid arthritis, the mode of action of LATS in the toxicosis occurring in underprivileged regions of thyroid itself and its association with other anti- severe iodine deficiency also give rise to diagnostic thyroid antibodies. difficulty. The demonstration of LATS has certainly The best physicians are not infallible; since thyro- explained why some mothers with treated or un- toxicosis can be corrected, if not cured, and each ofhttp://pmj.bmj.com/ treated thyrotoxicosis produce babies with congeni- the three treatments have their respective hazards tal or neonatal hyperthyroidism. The LATS and two are destructive (operation and radioiodine), immunoglobulin passes the placenta, and if in high it is essential that at least one reliable test is carried enough titre stimulates the young thyroid. This out even when the situation seems clear. The choice of thyrotoxicosis remits spontaneously, although tem- a single test obviously depends on local, regional and porary drug control may be necessary, as the LATS sometimes national resources. Nevertheless a few disappears from the circulation. This usually takes can laid down. guiding principles be on September 28, 2021 by guest. Protected place within a few weeks of birth. These comments are made to emphasize our rela- Serum PB1271, total thyroxine and T3 resin tests (Figs. tive ignorance about the processes involved in the 1-4 and Tables 2 and 3). initiation and maintenance of the commonest The author's view is that enough is now known syndrome of clinical thyrotoxicosis. Although about in vitro measurements of blood hormone levels direct measurements of blood TSH, blood TSH to advise their application in the first stage of diag- response to TRH and blood LATS levels are likely nostic decision making. In our view all patients to clarify some aetiological problems and even help should have chemical estimations of the serum pro- with diagnostically difficult cases, they are still tein bound iodine (PB1271), preferably carried out research tools. by autoanalyser; they should also have an estimation The ordinary clinician responsible for making of the serum total thyroxine using, for example, a diagnostic and therapeutic decisions about large competitive binding assay system of the type pro- numbers of patients, only some of whom will have duced by the Radiochemical Centre, Amersham thyrotoxicosis, really wants to know what there is in (Thyopac 4). When the serum PB1271 or the serum the laboratory to help him.
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