Diagnostic Considerations
Diagnostic considerations include factitious hyperthyroidism, which is hyperthyroidism secondary to intentional consumption of thyroid hormone. In this condition, thyroid hormone consumption causes suppression of thyroglobulin secretion by the thyroid. Factitious hyperthyroidism is common in medical personnel, who have easy access to medication containing thyroid hormone and may abuse it for weight loss or an energy boost.
Differential Diagnoses
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Severe proptosis, periorbital edema, and eyelid retraction from thyroid-related orbitopathy. This patient also had optic nerve dysfunction and chemosis (conjunctival edema) from thyroid-related orbitopathy.
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Color flow ultrasonogram in patient with Graves disease. Generalized hypervascularity is visible throughout gland (note red areas), which often can be heard as hum or bruit with stethoscope.
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Absence of iodine 123 (123I) radioactive iodine uptake in patient with thyrotoxicosis and subacute painless or lymphocytic thyroiditis. Laboratory studies at time of scan demonstrated the following: thyroid-stimulating hormone (TSH), less than 0.06 mIU/mL; total thyroxine (T4), 21.2 µg/dL (reference range, 4.5-11); total triiodothyronine (T3), 213 ng/dL (reference range, 90-180); T3-to-T4 ratio, 10; and erythrocyte sedimentation rate (ESR), 10 mm/hr. Absence of thyroid uptake, low T3-to-T4 ratio, and low ESR confirm diagnosis of subacute painless thyroiditis.
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Three multinuclear giant cell granulomas observed in fine-needle aspiration biopsy of thyroid from patient with thyrotoxicosis from subacute painful or granulomatous thyroiditis.
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Scan in patient with toxic multinodular goiter. 5-Hour 123I-iodine uptake was elevated at 28% (normal 5-15%). Note multiple foci of variably increased tracer uptake.
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Iodine 123 (123I) nuclear scintigraphy: 123I scans of normal thyroid gland (A) and common hyperthyroid conditions with elevated radioiodine uptake, including Graves disease (B), toxic multinodular goiter (C), and toxic adenoma (D).
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Gross photo of subtotal thyroidectomy for diffuse toxic goiter (Graves Disease) showing homogenous enlargement without nodules.
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Low-power photomicrograph showing diffuse papillary hyperplasia (hallmark histologic feature of Graves disease).
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High-power photomicrograph showing papillary hyperplasia of follicular cells with increased nuclear size and small nucleoli.
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Bilateral erythematous infiltrative plaques on lower extremities in 42-year-old man with Graves disease are consistent with pretibial myxedema. Myxedematous changes of skin usually occur in pretibial areas and resemble orange peel in color and texture.
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Hypothalamic-pituitary-thyroid axis feedback. Schematic representation of negative feedback system that regulates thyroid hormone levels. TRH = thyrotropin-releasing hormone; TSH = thyroid-stimulating hormone.
Tables
Common Forms (85-90% of Cases) |
24-Hour RAIU Over Neck* |
Diffuse toxic goiter (Graves disease) |
Increased (moderate to high: 40-100%) |
Toxic multinodular goiter (Plummer disease) |
Increased (mild to moderate: 25-60%) |
Thyrotoxic phase of subacute thyroiditis |
Decreased (very low: < 2%) |
Toxic adenoma |
Increased (mild to moderate: 25-60%) |
Less Common Forms |
|
Iodide-induced thyrotoxicosis |
Variable but usually low (< 25%) |
Thyrotoxicosis factitia |
Decreased (very low: < 2%) |
Uncommon Forms |
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Pituitary tumors producing TSH |
Increased (mild to moderate: 25-60%) |
Excess human chorionic gonadotropin (molar pregnancy/choriocarcinoma) |
Increased (variable: 25-100%) |
Pituitary resistance to thyroid hormone |
Increased (mild to moderate: 25-60%) |
Metastatic thyroid carcinoma |
Decreased |
Struma ovarii with thyrotoxicosis |
Decreased |
RAIU = radioactive iodine uptake; TSH = thyroid-stimulating hormone. * A normal 6-hour RAIU is approximately 2-16%; a 24-hour RAIU is about 8-25% but is modified according to the iodine content of the patient’s diet. RAIU or scanning should not be performed in a woman who is pregnant (with the exception of a molar pregnancy) or breastfeeding. |
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