The diagnosis of Graves’ disease is usually easily made. The combination of eye signs, goiter, and any of the characteristic symptoms and signs of hyperthyroidism forms a picture that can hardly escape recognition (Fig -1). It is only in the atypical cases, or with coexisting disease, or in mild or early disease, that the diagnosis may be in doubt. The symptoms and signs have been described in detail in the section on manifestations of Graves’ disease. For convenience, the classic findings from the history and physical examination are grouped together in Table 1a and 1b.These occur with sufficient regularity that clinical diagnosis can be reasonably accurate. Scoring the presence or absence and severity of particular symptoms and signs can provide a clinical diagnostic index almost as reliable a diagnostic measure as laboratory tests(1).
Occasionally diagnosis is not at all obvious.In patients severely ill with other disease, in elderly patients with “apathetic hypothyroidism”, or when the presenting symptom is unusual, such as muscle weakness, or psychosis, the diagnosis depends on clinical alertness and laboratory tests. The diagnosis of Graves’ Disease does not depend on thyrotoxicosis. Ophthalmopathy, or pretibial myxedema are seen without goiter and thyrotoxicosis, or even with spontaneous hypothyroidism. While proper classification can be debated, these patients seem to represent one end of the spectrum of Graves’ Disease. Thus we are usually making two coincident diagnoses:1)- Is the patient hyperthyroid? and 2)- Is the cause of the problem Graves’ disease.
|Table 1a SYMPTOMS|
|Table 1b PHYSICAL SIGNS|
Hyperpigmentation or vitiligo
LABORATORY DIAGNOSIS OF GRAVE’S DISEASE
Serum Hormone Measurements
TSH and FT4 assay–
Once the question of thyrotoxicosis has been raised, laboratory data are required to verify the diagnosis, help estimate the severity of the condition, and assist in planning therapy. A single test such as the TSH or estimate of FT4 (free T4) may be enough, but in view of the sources of error in all determinations, most clinicians prefer to assess two more or less independent measures of thyroid function. For this purpose, an assessment of FT4 and sensitive TSH are suitable. As an initial single test, a sensitive TSH assay may be most cost-effective and specific. TSH should be 0 – .1 µU/ml in significant thyrotoxicosis, although values of .1 – .3 are seen in patients with mild illness, especially with smoldering toxic multinodular goiter in older patients(1.1). TSH can be low in some elderly patients without evidence of thyroid disease. TSH can be normal — or elevated — only if there are spurious test results from antibodies, or the thyrotoxicosis is TSH-driven, as in a pituitary TSH-secreting adenoma or pituitary resistance to thyroid hormone.
Measurement of FT4 or FTI(Free thyroxine index)is also usually diagnostic.The degree of elevation of the FT4 above normal provides an estimate of the severity of the disease. During replacement therapy with thyroxine the range of both FTI and FT4 values tend to be about 20% above the normal range, possibly because only T4 , rather than T4 and T3 from the thyroid, is providing the initial supply of hormone. Thus many patients will have an FT4 or FTI above normal when appropriately replaced and while TSH is in the normal range. Except for this, elevations of FT4 not due to thyrotoxicosis are unusual, and causes are given in Table 3. Of course the Total T4 level may normally be as high as 16 or 20 µg/dl in pregnancy, and can be elevated without thyrotoxicosis in patients with familial hyperthyroxinemia due to abnormal albumin, the presence of hereditary excess TBG, the presence of antibodies binding T4 , the thyroid hormone resistance syndrome, and conditions listed in Table 3. The T4 level may be normal in thyrotoxic patients who have depressed serum levels of T4 -binding protein or because of severe illness, even though they are toxic. Thus, thyrotoxicosis may exist when the total T4 level is in the normal range.However measurement of FT4, FT3, or FTI usually obv