Scintigraphic manifistation of thyrotoxicosis
Upcoming SlideShare
Loading in...5
×

Like this? Share it with your network

Share
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
No Downloads

Views

Total Views
376
On Slideshare
376
From Embeds
0
Number of Embeds
0

Actions

Shares
Downloads
12
Comments
0
Likes
2

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. Scintigraphic Manifestations of Thyrotoxicosis Dr. Ahmed Abdo Harwn Nuclear Medicine Consultant 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 1
  • 2. LEARNING OBJECTIVES Review the thyroid physiology and iodin metabolism Discuss the distinction between thyrotoxicosis and hyperthyroidism. Identify the thyroid uptake and Scintigraphy findings in both the common and uncommon causes of thyrotoxicosis. Describe the therapeutic approach for the patient with thyrotoxicosis. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 2
  • 3. Thyroid physiology Follicle • is the functional unit composed of thyroid follicular cells (Thyrocyts) that surround secreted colloid. The follicular cell • polarized—the basolateral surface is apposed to the bloodstream and an apical surface faces the follicular lumen. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 3
  • 4. Thyroid physiology Thyroid hormone level is monitored by: • hypothalamic supraoptic nuclei • thyrotrophs of the anterior pituitary gland. Reduced levels of thyroid hormone: • increase basal TSH production • enhance TRH-mediated stimulation of TSH TSH-R stimulate adenylate cyclase and activate cAMP cascade. • • • • This stimulate NIS to trap iodide Stimulate producing thyroglobulin Stimulate hormone synthesis Stimulate release of thyroid hormones. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 4
  • 5. Thyroid physiology High thyroid hormone • Suppress TSH gene expression secretion • Inhibit TRH stimulation of TSH Thyroid hormones return to its normal level The thyroid axis is a classic example of an endocrine feedback loop. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 5
  • 6. Iodine metabolism 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 6
  • 7. Deficiency: Goiter • Children-diffuse goiters, • Adults-nodular goiters. Hypothyroidism. Critinism: most extreme manifestation of IDD Decreased fertility rate increased infant mortality Mental retardation: •Worldwide, iodine deficiency is the leading cause of preventable mental retardation , low IQ , and poor mental and psychomotor development (predominantly in language and memory skills). •Reduction in IQ in affected youth from regions of severe and mild iodine deficiency. •exaggerated in the setting of concomitant deficiencies of selenium or vitamin A. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 7
  • 8. Daily allownce Normal daily Dietary intake:The US Institute of Medicine (IOM) recommended dietary allowance (RDA) • 150 mcg/d of iodine for adults and adolescents, • 220 mcg/d for pregnant women, • 290 mcg/d for lactating women, • 90-120 mcg/d for children aged 1-11 years. • The adequate intake for infants is 110-130 mcg/d. Absorption: GI • 100% regardless of the plasma level 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 8
  • 9. Excretion: • Kidneys: 80% of daily intake • 24-hour urine collection • a median of 50-100 mcg of iodine per liter is consistent with mild iodine deficiency, • 20-49 mcg of iodine per liter is consistent with moderate deficiency, • and less than 20 mcg of iodine per liter is consistent with severe deficiency. • Fecal loss 15 μg/day • Minimal amount in sweat. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 9
  • 10. Iodine Sources medications: Natural source: • • • • • Vitamin preparation • Cough medications • Amiodaron Drinking water Dairy products Sea food Kelp Red food coloring Supplement in • Bread (150 microgram per slice) • Cooking oil • Table salt (30 mcg / gram salt) 1 December 2011 Radiographic contrast • 100ml contains : 30, 000, 000 μg of iodine = 100, 000 times the normal daily dietary intake. Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 10
  • 11. Iodide pools: Intra-thyroidal organic iodine pool: • Greatest = 6000 μg iodine. Extra-thyroidal organic iodine pool: • ( thyroid hormones in circulation) = 500 µg Inorganic free iodide pool: • • • • in circulation =375 µg 300 µg from daily intake 60 µg from deiodination of thyroid hormones 10 µg thyroid iodide leakage 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 11
  • 12. Excess amount of Iodide in Normal person. Excess amount of Iodide Intrathyroidal iodide level increases Intrathyroidal iodide reaches critical level Inhibit thyroid hormone formation (Wolff-Chaikoff effect) The hormone level goes down below the normal level Thyroid hormones level rises initially. 1 December 2011 Soon return to normal through an escape phenomenon. Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 12
  • 13. Excess Iodide in abnormal situation in chronic inflammation like Hashimot;s thyroiditis Iodine deficient areas Patients with MNG Excess amount of iodide Excess amount of iodide Increased thyroid hormone levels Increased thyroid hormone levels No ((Wolff-Chaikoff effect) (Wolff-Chaikoff effect) The hormone level goes down below the normal level No escape phenomenon Thyrotoxicosis (iodide-induced) (Jod-Basedow phenomenon) 1 December 2011 Hypothyroidism (iodide-induced) Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 13
  • 14. Thyroid Hormone synthesis Iodide trapping • Stimulated by TSH, TSI • Inhibited by competition from large molecules Like TcO4 , • Blocked by exogenous Thyroxin • loss of iodide trapping function in thyroid cancer associated with failure of radioiodine treatment. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 14
  • 15. Thyroid Hormone synthesis Organification (Oxidative iodination) & iodination • MIT or DIT • Stimulated by TSH • Inhibited by methimazole, PTU, lithium, excess iodide. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 15
  • 16. Thyroid Hormone synthesis Coupling of iodo-tyrosine 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 16
  • 17. Thyroid Hormone synthesis Release. (last come , first served) stimulated by TSH inhibited by lithium, excess iodide. 90% of the released thyroid hormone is in the form of T4, and 10% in the form of T3. The great majority of T3 (80-90%) is produced by the peripheral conversion of T4. The metabolic activity of thyroid hormone is determined by the amount of free T3 and free T4. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 17
  • 18. Thyroid hormone action Increases tissue O2 consumption Increases glucose use Regulate the body’s metabolism and heat production. Increases lipolysis Increases urinary nitrogen excretion 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 18
  • 19. Signs and symptoms 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 19
  • 20. Thyrotoxicosis • Clinical syndrome of increased systemic metabolism that results when the serum concentrations of free thyroxin, free triiodothyronine, or both are elevated Hyperthyroidism • Overactivity of the thyroid gland with a resultant increase in thyroid hormone synthesis and release into the systemic circulation 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 20
  • 21. Classification of thyrotoxicosis Increased thyroid function • • • • Graves disease Marine-Lenhart syndrome, toxic autonomous nodule, toxic multinodular goiter) Thyroid inflammation • subacute thyroiditis • silent thyroiditis, • Post partum thyroiditis Iodine-induced hyperthyroidism. Thyrotoxicosis of Extrathyroidal Origin • Factitious Hyperthyroidism, • Metastatic thyroid cancer, • Toxic struma ovarii Thyrotropin-induced hyperthyroidism (pituitary adenoma). 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 21
  • 22. Graves Disease (diffuse toxic goiter) History: • 24-year-old woman. Laboratory: • • • • T4 = 16.7 μg/dL, T3 = 311 ng/dL, TSH < 0.01 μIU/mL. 24-hour RAIU was 84%. Findings: • Enlarged gland. • The target-to-background activity is increased t • appearance of the pyramidal lobe (large arrow). 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 22
  • 23. Graves Disease (diffuse toxic goiter) PATH PHYSIOLOGY: • most common cause of thyrotoxicosis • an autoimmune disorder characterized by the presence of Thyroid Stimulating Immunoglobulin (TSI) or Thyroid-Stimulating Antibody (TSAb). • TSI is found in 90 to 95% of cases of Graves disease. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 23
  • 24. Graves Disease (diffuse toxic goiter) The RAIU • usually elevated at 24 hours. • Occasionally, normal in rapid iodine turnover, in severe cases. (4hrs is useful) 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 24
  • 25. Therapy Antithyroid medication: • Normal sized gland • mild severity. I-131 therapy • • • • modality of choice except in pregnant Lactating severe ophthalmopathy Surgery: Thyroidectomy • in marked thyromegaly with tracheal compression 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 25
  • 26. Marine-Lenhart Syndrome History: • 52-year-old woman. Laboratory values: • free T4 = 2.9 ng/dL, • T3 = 181 ng/dL, • TSH < 0.01 μIU/mL. Scan: • enlarged thyroid • diffusely increased radiotracer trapping, as in Graves disease per se. • However, within the gland are distinct cold nodules . 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 26
  • 27. Marine-Lenhart Syndrome Graves disease • coexists with TSH-dependent cold thyroid nodules Other names: • Graves disease coexistent with a multinodular goiter. • Nodular Graves disease. The RAIU • Elevated. Therapy: • Further evaluation for the cold nodules. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 27
  • 28. Toxic Autonomous Nodule (toxic adenoma) History: • 49-year-old woman LAB: • • • • T4 = 15.1 μg/dL, T3 = 304 ng/dL, TSH < 0.01 μIU/mL The 24-hour RAIU was elevated (46%). Scan : • hot nodule occupies most or all of the right thyroid lobe with near-total suppression of the left lobe . • The background activity is diminished to such an extent that the salivary glands are barely visualized. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 28
  • 29. Toxic Autonomous Nodule (toxic adenoma) Mechanism of formation: • TSH receptors on the adenoma surface undergo gene mutation, resulting in their continuous activation The RAIU • mildly to moderately elevated or occasionally is in the upper range of normal. Therapy: • I-131 is the preferred therapy • surgical removal of the toxic nodule. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 29
  • 30. Toxic Multinodular Goiter History: • 71-year-old man with anxiety and weight loss. Laboratory values: • T4 = 12.1 μg/dL, • T3 = 299 ng/dL, • TSH < 0.01 μIU/mL • The RAIU was 17% at 6 hours and 37% at 24 hours. Scan: • enlarged thyroid with overall nonuniform uptake. • Areas of both increased and decreased activity are scattered throughout the gland 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 30
  • 31. Toxic Multinodular Goiter Clinical diagnosis • on palpation and diagnostic imaging of multiple (ie, two or more) nodules in the thyroid. • The thyroid hormone levels are mildly elevated and the TSH level is suppressed Scintigraphy : • heterogeneous appearance • Functioning (hot) nodules scattered within suppressed extranodular thyroid tissue. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 31
  • 32. Toxic Multinodular Goiter The RAIU: • normal or slightly elevated. Therapy: • I-131 is most frequently used • Surgical • very large goiter, with airway compression • substernal extension of the goiter 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 32
  • 33. Subacute thyroiditis History: • 32-year-old woman with relatively rapid onset of palpitations, insomnia, anxiety, neck pain, and mood swings, all of which were preceded by an upper respiratory tract infection. Physical examination: • neck tenderness. Laboratory values: • • • • Free T4 = 2.5 ng/dL, free T3 = 640 ng/L, TSH < 0.01 μIU/mL. The 24-hour RAIU was 0.5%. Scan: • minimal thyroid activity (arrow) only slightly higher than background activity. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 33
  • 34. Subacute thyroiditis Other names: • subacute granulomatous thyroiditis • giant cell thyroiditis, • de Quervain thyroiditis Cause: upper respiratory tract infection with postviral inflammatory response (giant cell infiltration ) follicular swelling stretching of the thyroid capsule with subsequent pain and tenderness to palpation disruption with release of stored thyroid hormone. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 34
  • 35. Subacute thyroiditis RAIU • very low since the affected thyroid is unable to transport or organify iodine. Scintigrahy: • no or minimal activity within the gland Treatment: • Supportive: Salicylates and other nonsteroidal antiinflammatory. • steroids are the most effective therapy. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 35
  • 36. Silent Thyroiditis History: • 28-year-old woman. Thyrotoxic • No neck tenderness. Laboratory values: • • • • T4 = 21 μg/dL, T3 = 289 ng/dL, TSH < 0.02 μIU/mL. The 24-hour RAIU was 0.6%. Scan: • barely visible thyroid • prominent salivary glands • a large-core needle biopsy was performed, which demonstrated lymphocytic infiltrations within the thyroid parenchyma. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 36
  • 37. Silent Thyroiditis Other names: • painless thyroiditis, • atypical thyroiditis, • subacute lymphocytic thyroiditis) Cause: • Autoimmune disease • The thyroid peroxidase antibody levels are elevated, as well as the thyroglobulin antibody titer. • An autoimmune response initiates an infiltration of lymphocytes, leading to disruption, with subsequent release of excess thyroid hormone, • No neck pain or tenderness due to less follicular swelling compared with the giant cell infiltration and edema characteristic of subacute thyroiditis. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 37
  • 38. Silent Thyroiditis Self-limiting Course: Lasts from several weeks to several months followed by a period of transient hypothyroidism, which in turn is followed by complete recovery to the euthyroid state. This disorder can recur at any time, and about 10% of patients will have recurrent episodes of thyroiditis. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 38
  • 39. Silent Thyroiditis TFT: • Serum T3 and T4 levels are high • TSH level is very low. RAIU • very low, as with subacute thyroiditis, secondary to cell damage. Thyroid Abs • The thyroid peroxidase antibody levels, and the thyroglobulin antibody are elevated ESR is normal. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 39
  • 40. Silent Thyroiditis Acute phase: minimal radiotracer concentration by the thyroid on scans because of the associated follicular cell damage the RAIU increases and the Recovery scan demonstrates diffusely phase increased activity ―rebound‖ phenomenon. confusion with Graves disease 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 40
  • 41. Postpartum thyroiditis seen in • 5 % of post-partum patients. Pathophysiology: • It is subtype of silent thyroiditis that appears 2 to 12 months after delivery (most commonly between 4 to 6 months). The course of the disease : • similar to silent thyroiditis • thyrotoxicosis lasts 2 to 6 weeks and this is followed by • a period of hypothyroidism which also lasts 2 to 6 weeks. Prognosis: • 20-33% of patients with postpartum thyroiditis will become permanently hypothyroid. Recurrence: • The disorder tends to recur with multiple pregnancies 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 41
  • 42. Iodine-induced Hyperthyroidism (Jod-Basedow phenomenon). History: • 68-year-old man. • His history was significant for amiodarone therapy for intractable atrial fibrillation. Laboratory values: • • • • free T4 = 1.7 ng/dL, T3 = 351 ng/dL, TSH = 0.05 μIU/mL. The 24-hour RAIU was 2.7%. Scan: • decreased radiotracer trapping throughout the thyroid. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 42
  • 43. Iodine-induced Hyperthyroidism (JodBasedow phenomenon). Cause: • occurs insidiously when there is an excessive exposure to iodine in multinodular goiter, in endemically iodine-deficient areas. • Does not occur in normal person due to protective mechanism Wolff-Chaikoff effect. thyroid hormone levels: • are elevated, • TSH level is suppressed, RAIU • low (The RAIU is inversely proportional to the iodine pool within the thyroid.) Scintigraphy : • diminished tracer concentration uniformly, Treatment: • Antithyroid drugs in high doses, with or without potassium perchlorate, which blocks further iodine uptake by the gland • If this regimen is unsuccessful, steroids are warranted 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 43
  • 44. History: • 72-year-old male physician who was admitted to the hospital with multiple premature ventricular contractions. thyroid function testing, • • • • free T4 = 5.5 ng/dL T3 = 150 ng/dL, TSH < 0.01 μIU/mL. The I-123 RAIU at 24 hours was low (2%). Scan: • shows decreased activity throughout the thyroid. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 44
  • 45. Factitious Hyperthyroidism DDx iodine-induced hyperthyroidism was not considered because there was no known previous iodine administration. silent thyroiditis. The thyroid peroxidase Ant and antithyroid Ab are not elevated. serum thyroglobulin level, which was undetectable; confirming the diagnosis of ????????????? When confronted with this information, the patient admitted he was secretly taking L-thyroxine to ―enhance sexual potency.‖ 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 45
  • 46. History: • 53-year-old man with history of subtotal thyroidectomy for follicular thyroid cancer 5 years earlier. On suppressive dose of L-T4 • Presented with a mass compressing the lower thoracic spinal cord • Biopsy of the mass revealed metastatic follicular thyroid cancer. • In preparation for I-131 ablation, L-thyroxine therapy was stopped for 5 weeks. However, the thyrotoxic symptoms persisted; 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 46
  • 47. Lab: • free T4 level was 2.6 ng/dL, • the free T3 level was 752 ng/L, • the TSH level was 0.02 μIU/mL. Computed tomography (CT) of the chest • a destructive mass in the right lung. • The diagnosis of thyrotoxicosis caused by metastatic follicular thyroid cancer was made. I-131 ablation was then considered. Thallium-201 whole-body scanning was performed immediately before I-131 ablation. • Anterior Tl-201 whole-body image shows metastases in the right chest wall • thoracic spine. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 47
  • 48. 200 mCi (7,400 MBq) of I-131 was given as RAI treatment Postablation I-131 scan obtained 1 week • • • • show thyroid bed uptake right infraclavicular lymph node chest wall metastasis thoracic spine lesion 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 48
  • 49. Metastatic Thyroid Cancer Rare to develop thyrotoxicosis. pathogenesis is unknown, (thyroidstimulating immunoglobulins) The diagnosis: whole-body imaging or by postablation I-131 scanning. Treatment: • 131 • ?? Surgery in single metastasis is causing the thyrotoxicosis, 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 49
  • 50. History: • 81-year-old woman with thyrotoxicosis, ascites, and a pelvic mass. Laboratory values: • T4 = 13.7 μg/dL, • T3 = 200 ng/dL, • TSH < 0.01 μIU/mL. pelvic CT. • left ovarian mass 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 50
  • 51. Struma Ovarii Tc-99m pertechnetate: • decreased tracer activity in a small thyroid The 24-hour RAIU • 3%. Pelvic scan was also performed. • pelvic mass (arrowhead) displacing the bladder to the right (arrow). I-123 scan for pelvis. • Bottom left: I-123 image obtained after voiding shows the mass (arrow). 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 51
  • 52. Struma Ovarii After surgery: • Thyroid function soon returned to normal. Two months later: • 24-hour RAIU was 16%; • Tc-99m pertechnetate scanning shows normal tracer concentration. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 52
  • 53. Struma Ovarii very rare teratomatous ovarian tumour tumor that contains functioning thyroid tissue. It is usually benign and is most commonly discovered by the pathologist when an ovarian tumor is removed In a minority of cases, however, the tumor behaves autonomously and produces excess thyroid hormone. Strong clinical suspicion for their diagnosis, comes from signs and symptoms relating to the abdomen or pelvis. TFT: • Serum T3 and T4 levels are elevated, • TSH level is suppressed. • RAIU is low Thyroid scan • faint visualization of the gland or nonvisulaization. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 53
  • 54. TSH-induced Thyrotoxicosis History: • 33-year-old woman. Laboratory values: • free T4 = 2.0 ng/dL, • T3 = 191 ng/dL, • TSH = 37.1 μIU/mL. Tc-99m pertechnetate image: • relatively high target-to-background activity CT of the brain • revealed a pituitary tumor. Upon removal of the tumor, the symptoms subsided and thyroid function returned to normal. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 54
  • 55. Conclusions The patient with thyrotoxicosis is a diagnostic challenge to the clinician, symptoms can be mild to severe, signs can be subtle to obvious. Signs and symptoms are identical regardless of the cause. Cause must be determined for appropriate management and therapy. The history and physical examination, along with thyroid function tests, enable correct interpretation of the thyroid scan and to make the diagnosis of thyrotoxicosis RAIU and thyroid scintigraphy are useful in narrowing the differential diagnosis of Thyrotoxicosis 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 55
  • 56. References Harrison's Principles of Internal Medicine, 18e Nuclear Medicine 2e, Robert E. Henkin Radiographics, “Scintigraphic manifestation of thyrotoxicosis” Charles M. Intenso et al Iodine Deficiency Workup, • Author: Stephanie L Lee, MD, PhD; Chief Editor and et al. 1 December 2011 Scintigraphic manifistations of thyrotoxicosis – Dr.Ahmed Harwn 56