ESSENTIALS OF DIAGNOSIS
Sweating, weight loss or gain, anxiety, palpitations, loose stools, heat intolerance, menstrual irregularity.
Tachycardia; warm, moist skin; stare; tremor.
Graves disease is most common cause of hyperthyroidism; palpable goiter (sometimes with bruit) seen in most patients; ophthalmopathy also common.
Suppressed TSH in primary hyperthyroidism; usually increased T4, FT4, T3, FT3.
The term “thyrotoxicosis” refers to the clinical manifestations associated with elevated serum levels of T4 or T3 that are excessive for the individual (hyperthyroidism). Serum TSH levels are suppressed in primary hyperthyroidism. However, certain drugs and conditions can affect laboratory tests and lead to the erroneous diagnosis of hyperthyroidism in euthyroid individuals (Table 26–4). The causes of hyperthyroidism are many and diverse, as described below.
Table 26–4.Factors that can cause aberrations in laboratory tests that may be mistaken for spontaneous clinical primary hyperthyroidism.1 ||Download (.pdf) Table 26–4. Factors that can cause aberrations in laboratory tests that may be mistaken for spontaneous clinical primary hyperthyroidism.1
|High Serum T4 or T3 ||Low Serum TSH |
Collection vial contains gel barrier for T3
Acute psychiatric problems (30%)
Acute medical illness (eg, acute intermittent porphyria)
Acute or chronic active hepatitis, primary biliary cirrhosis
AIDS (increased thyroid-binding globulin)
Familial thyroid-binding abnormalities
Familial resistance to thyroid (Refetoff syndrome)
Pregnancy: morning sickness, hyperemesis gravidarum
Heparin (dialysis method)
Thyroid hormone therapy (excessive or factitious)
Autonomous thyroid or thyroid nodule
Corticosteroid administration (acute)
Calcium channel blockers (nifedipine, verapamil)
hCG-secreting trophoblastic tumors
Nonthyroidal illness (severe)
Pregnancy (especially with morning sickness)
Suppression after recent therapy for hyperthyroidism
TSH variants not detected by commercial assays
Graves disease (known as Basedow disease in Europe) is the most common cause of thyrotoxicosis. It is an autoimmune disorder affecting the thyroid gland, characterized by an increase in synthesis and release of thyroid hormones (eFigure 26–7); autoantibodies known as thyroid-stimulating immunoglobulins (TSI) or TSH receptor antibodies bind to the TSH receptor in thyroid cell membranes and stimulate the gland to hyperfunction.
Graves disease. (Used, with permission, from P Forsham, MD.)
Graves disease is much more common in women than in men (8:1), and its onset is usually between the ages of 20 and 40 years. It may be accompanied by infiltrative ophthalmopathy (Graves exophthalmos) and, less commonly, by infiltrative dermopathy (pretibial ...