Radioactive Iodine Uptake
Radioactive Iodine Uptake: Excerpt from A Pocket Manual of Differential Diagnosis
Factors Causing Increased Uptake
Reflecting increased hormone synthesis
Excessive hormone losses
Chronic diarrhea states
Nephrosis
Soybean ingestion
Hyperthyroidism
Response to glandular hormone depletion
Rebound after suppression of TSH
Recovery phase of silent, subacute, or other transient destructive thyroiditis
Rebound phase after withdrawal of iodide or other antithyroid drugs (if TSH is elevated)
Not reflecting increased hormone synthesis
Iodide deficiency
Dietary
Excessive loss
Dehalogenase defect
Pregnancy
Hashimoto's thyroiditis (if TSH is elevated)
Inherited disorders of thyroid hormone synthesis (except for iodide trapping defects)
Lithium administration
Factors Causing Decreased Uptake
Reflecting decreased hormone synthesis
Primary hypofunction
Drugs (other than those containing iodide)
Major effect
Glucocorticoids (in large doses, acutely)
Paraaminobenzoic acid
Perchlorate
Salicylates (>5 g/day)
Sulfonamides
Thiocyanate
Thioamides
Carbimazole
Methimazole
Propylthiouracil
Minor effect
Aminoglutethimide
Phenylbutazone
Resorcinol (topical)
Sulfonylureas
Secondary (pituitary) or tertiary (hypothalamic) hypothyroidism
Some hormone biosynthetic defects (especially defects in iodide trapping)
Status post thyroidectomy, radioiodine, or external radiotherapy to the head/neck
Hashimoto's thyroiditis (end stage)
Transient thyroiditis (active phase)
Postpartum thyroiditis
Silent (painless) thyroiditis
Subacute (DeQuervain's, granulomatous) thyroiditis
Secondary hypofunction
Exogenous thyroid hormone
Not reflecting decreased hormone synthesis
Certain types of thyrotoxicosis
Rapid hormone release owing to very severe hyperthyroidism (rare)
Increased nonradioactive iodide exposure
Cardiac or renal failure with iodide retention
Increased dietary iodide
Pharmacologic iodide exposure
Amiodarone
Other iodine-containing drugs
Iodide-containing x-ray contrast agents
References
1. Larsen PR, Davies TF, Hay ID: The Thyroid Gland, pp. 410–412. See Bibliography, 3.
2. Cavalieri RR, McDougall IR: In Vivo Isotopic Tests and Imaging, pp. 355–357. See Bibliography, 4.
Book Source Details
- Book Title: A Pocket Manual of Differential Diagnosis
- Author(s): Stephen N. Adler, Dianne B. Gasbarra
- Year of Publication: 1999
- Copyright Details: A Pocket Manual of Differential Diagnosis, Copyright © 1999 Lippincott Williams & Wilkins.
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