Practical Therapeutics Drugs 14: 376-382 (1977) e ADIS Press 1977
Thyroid Disease: Recognition and Management B£.W. Brownlie Christchurch Hospital. Christchurch
Thyroid dysfunction is a common cause of ill health, but too often diagnosis is made only after some considerable delay. During the last 10 years there has been a marked increase in our understanding of the pathophysiology of thyroid disorders. This has largely been due to the development of specific radioimmunoassays for the measurement of serum thyroxine (T4 ) , serum tri-iodothyronine (TJ ) and thyrotrophin (TSH). The physiological importance of the second major thyroid hormone T J has been established and a new syndrome recognised - T J toxicosis, where thyrotoxicosis occurs in patients with elevated serum T J but normal serum T 4 levels. The ability to measure plasma TSH has led to a better understanding of the factors regulating the pituitary-thyroid axis and has provided a very sensitive index of early thyroid failure - lack of the negative feedback of normal thyroid hormone on the pituitary , leading to an elevation in TSH.
index. Although the total serum T 4 level is usually an adequate index of thyroid function, the value should always be adjusted for serum protein abnormalities with the calculation of a free thyroxine index (free T4 index). Unfortunately, different laboratories express
J. The Rational Use of Thyroid Function Tests The availability of specific thyroid function tests should lead to earlier diagnosis. The best routine thyroid function test to screen patients for hypothyroidism or thyrotoxicosis is the free thyroxine
a
Thyroid Disease
377
tives, and in patients with complicating illness such as renal failure. The free thyroxine index alone is usually sufficient in most clinical situations, but occasionally additional tests are necessary (see table 0. If marginal or discordant results are obtained, clinical reassessment and possibly repeat tests should be arranged . Radioisotopic thyroid scans (fig. I) are of some value in the assessment of thyroid nodules - a 'cold' nodule is one which does not actively take up isotope and may indicate degenerative, cystic or neoplastic change; a 'hot' nodule with increased isotope uptake is often associated with thyrotoxicosis.
2. Recognition and Management ofIndividual Thyroid Diseases 2.1 Thyrotoxicosis
c
Fig. t. ggmTc Pertechnetate thyroid scans. a) Diffuse thyroid hyperplasia - Graves' disease. b) Toxic multinodular goitre. c) Toxic uninodular goitre - toxic goitre .
their results in a variety of ways. e.g. free thyroxine index. adjusted serum T 4' etc. The adjustment of total serum T 4 levels for serum protein change is especially important in patients on drugs such as oral contracep-
2. J.J Recognition The clinical diagnosis of the young woman with classical textbook features including eye signs should not prove to be too difficult, but recent attention has been drawn to the large pool of undiagnosed elderly patients with thyrotoxicosis . In the Canterbury area of New Zealand, which was an iodine deficiency area prior to the introduction of iodised salt more than 30 years ago. the majority of thyrotoxic patients are in the 50 plus age group. Many such patients have longstanding goitres and non-specific symptoms. Cardiac failure with atrial fibrillation may be the first indication of thyrotoxicosis . Usually. a free T 4 index alone is sufficient to confirm the clinical diagnosis of thyrotoxicosis, but a serum T J is invaluable if the results are marginal. When the clinical picture is suggestive of thyrotoxicosis and the laboratory results
Thyroid Disease: Recognition and Management B£.W. Brownlie Christchurch Hospital. Christchurch
Thyroid dysfunction is a common cause of ill health, but too often diagnosis is made only after some considerable delay. During the last 10 years there has been a marked increase in our understanding of the pathophysiology of thyroid disorders. This has largely been due to the development of specific radioimmunoassays for the measurement of serum thyroxine (T4 ) , serum tri-iodothyronine (TJ ) and thyrotrophin (TSH). The physiological importance of the second major thyroid hormone T J has been established and a new syndrome recognised - T J toxicosis, where thyrotoxicosis occurs in patients with elevated serum T J but normal serum T 4 levels. The ability to measure plasma TSH has led to a better understanding of the factors regulating the pituitary-thyroid axis and has provided a very sensitive index of early thyroid failure - lack of the negative feedback of normal thyroid hormone on the pituitary , leading to an elevation in TSH.
index. Although the total serum T 4 level is usually an adequate index of thyroid function, the value should always be adjusted for serum protein abnormalities with the calculation of a free thyroxine index (free T4 index). Unfortunately, different laboratories express
J. The Rational Use of Thyroid Function Tests The availability of specific thyroid function tests should lead to earlier diagnosis. The best routine thyroid function test to screen patients for hypothyroidism or thyrotoxicosis is the free thyroxine
a
Thyroid Disease
377
tives, and in patients with complicating illness such as renal failure. The free thyroxine index alone is usually sufficient in most clinical situations, but occasionally additional tests are necessary (see table 0. If marginal or discordant results are obtained, clinical reassessment and possibly repeat tests should be arranged . Radioisotopic thyroid scans (fig. I) are of some value in the assessment of thyroid nodules - a 'cold' nodule is one which does not actively take up isotope and may indicate degenerative, cystic or neoplastic change; a 'hot' nodule with increased isotope uptake is often associated with thyrotoxicosis.
2. Recognition and Management ofIndividual Thyroid Diseases 2.1 Thyrotoxicosis
c
Fig. t. ggmTc Pertechnetate thyroid scans. a) Diffuse thyroid hyperplasia - Graves' disease. b) Toxic multinodular goitre. c) Toxic uninodular goitre - toxic goitre .
their results in a variety of ways. e.g. free thyroxine index. adjusted serum T 4' etc. The adjustment of total serum T 4 levels for serum protein change is especially important in patients on drugs such as oral contracep-
2. J.J Recognition The clinical diagnosis of the young woman with classical textbook features including eye signs should not prove to be too difficult, but recent attention has been drawn to the large pool of undiagnosed elderly patients with thyrotoxicosis . In the Canterbury area of New Zealand, which was an iodine deficiency area prior to the introduction of iodised salt more than 30 years ago. the majority of thyrotoxic patients are in the 50 plus age group. Many such patients have longstanding goitres and non-specific symptoms. Cardiac failure with atrial fibrillation may be the first indication of thyrotoxicosis . Usually. a free T 4 index alone is sufficient to confirm the clinical diagnosis of thyrotoxicosis, but a serum T J is invaluable if the results are marginal. When the clinical picture is suggestive of thyrotoxicosis and the laboratory results
