Diagnosis of thyroid disease(Radio active iodine uptake) pptx

This slide is mainly about radioactive uptake of iodine in diagnosis of thyroid

1. Thyroid diagnosis

2. The thyroid uptake and scan is a radiologic diagnostic tool used to determine the thyroid function and pathologies. This diagnostic procedure works on the principle of the unstable nuclide of the atom, which tries to attain stability by releasing an alpha, beta, and gamma rays

3. The test uses a radioactive tracer, which is a protein or a molecule attached to radioactive material. The radioactive tracer is administered into the patient, and a probe measures the amount of iodine uptake by the thyroid gland. The thyroid scan checks for the even spread of the tracer in the gland. 

4. More than 20 radioactive tracers exist, of which two isotopes of iodine I-123 and I-131 and 99m-technetium pertechnetate , are the usual agents used in this test. I-131 has a longer half-life than I-123, so I-123 is used more frequently than I-131 due to less radiation exposure to the body. 99m-Technetium pertechnetate is an analog of iodine, so it gets transported to the thyroid gland similarly to iodine.   111In-pentoxide, thallium-201 ( 201T1), 99mTc-sestamibi, 99mTc-tetrofosmin are some of the less commonly used radioactive tracers in this test. [1]  This test is different than radioactive iodine therapy, which treats thyroid cancers

5. Procedure Clinicians usually perform the thyroid uptake and scan in the outpatient setting. . The patient can be allergic to the radiotracer, so careful evaluation is necessary. If a patient is taking antithyroid medications such as methimazole or propylthiouracil , they should receive instructions to hold these medications for at least five days.  Prior studies of the thyroid gland and baseline TSH and free T4 levels are necessary before the test. In thyroid cancer patients, thyroglobulin and thyroglobulin antibodies may also need to be checked.

6. Radiotracer is given to the patient intravenously or orally. The timing of radiotracer administration before the scan varies according to the route . The patients are asked to take oral radiotracer 24 hours before the scan, or they are injected with radiotracer 30 minutes before the scan. Sodium iodide symporters located on the cells of the thyroid gland are responsible for uptaking radioactive iodine. The patient will then lie down on the movable examination table, and the gamma camera takes serial images of the thyroid gland from three different angles. The patient should lie still at the time of capturing images. The clinical history, thyroid examination, and the thyroid function tests, all merit consideration while interpreting the results of this test

7. Indications The indications of thyroid uptake and scan are as follows  [3][4][5] : Differential diagnosis of hyperthyroidism Suspected thyroid cancer Suspected metastasis of thyroid cancer Thyroid nodule Thyroid inflammation Determine the efficacy of radioactive iodine therapy Organification (incorporation of iodine into thyroglobulin) defects Determine congenital thyroid defects

8. Potential diagnosis Graves disease. Toxic nodular goiter Toxic adenoma Thyroiditis Congenital defect of thyroid hormone synthesis Iodine deficiency The recovery from subacute, silent, or postpartum thyroiditis Destructive thyroiditisSubacute thyroiditis Silent thyroiditis Postpartum thyroiditis 

9. The normal values of thyroid uptake of radiotracer are 3 to 16% at 6 hours and 8 to 25% at 24 hours. These values may change according to laboratory standard techniques or patient dietary habits. The thyroid gland can uptake more or less than normal. More than normal uptake of radioactive iodine by the thyroid gland indicates hyperactive thyroid and less than normal uptake infers hypoactive thyroid gland, or interference with the uptake 

10. Following are some of the causes of increased uptake of radiotracer: 1) Hyperthyroidism due to Graves, multinodular goiter or thyroid adenoma 2) Goiter 3) Early-stage of Hashimoto thyroiditis 4) Iodine deficiency 5) The recovery phase from subacute , silent, or postpartum thyroiditis 6) Pregnancy 7) Lithium carbonate therapy 8) Withdrawl of antithyroid medication 9) Rebound after the suppression of thyrotropin 10) Congenital defects of thyroid hormone synthesis Some of the causes of decreased uptake of radiotracer are as follows: P rimary hypothyroidism 2) Central hypothyroidism 3) Destructive thyroiditis Subacute thyroiditis Silent thyroiditis Postpartum thyroiditis 4) Excess iodine 5) Dietary supplements 6) Radiological contrast 7) Medications Amiodarone,Antithyroid drugs, Perchlorate, Thiocyanate , Sulphonamides, Sulphonylurea , High-dose glucocorticosteroids , Topical iodine 8) Post-thyroidectomy 9) External neck radiation

11. Factors that clinician should consider before conducting thyroid uptake and scan are as follows  [7] : Diarrhea that can decrease the absorption of the dye if given orally Head CT with oral or intravenous contrast within the past two weeks Unacceptable quantity of iodine in the diet Hypochloremia that can increase the absorption of the radiotracer Iodine containing drugs (amiodarone) Thyroid hormone replacement and antithyroid drugs Chronic renal failure that impairs iodide clearance, expands the iodide pool, and lowers the %RAIU

12. Complications Radioactive iodine uptake and scan is a safe procedure. Some of the complications of this procedure are as follows  [8] : Pain at the injection site Hypersensitivity and anaphylaxis to radiotracer Exposure of the fetus or baby, if performed during pregnancy or lactating period

13. Patient Safety and Education The following precautions are necessary before performing a thyroid uptake scan: Pregnancy should be ruled out with either serum or urine pregnancy test, and the clinician should ask the patient to avoid pregnancy for six months after radioactive iodine administration. The patient should avoid breastfeeding after performing this test as radioactive iodine can be secreted in breast milk. This test should be administered by a trained professional. The patient should receive counseling regarding physical contact safety measures by avoiding the exposure of his/her urine, stool, saliva, vomit, blood, and body fluids as well as perspiration for 48 hours. Patients should also avoid public transportation and sitting close to others. Patients should carry documents indicating the date, provider information, and radionuclide used while traveling through port of entry within four months of the procedure. Patients should receive counseling on flushing twice after urinating or defecating for 24 to 48 hours after the procedure

14. Diagnosis of thyroid disease.

15. Diagnosis

16. Thyroid function study results in hyperthyroidism and thyrotoxicosis are as follows: Hyperthyroidism and thyrotoxicosis are marked by suppressed TSH levels and elevated T3 and T4 levels Patients may have normal free thyroxine levels but have elevation of T3 levels, with a suppressed TSH level; this condition is known as T3 thyrotoxicosis and is usually associated with early Graves disease and toxic thyroid adenoma Subclinical hyperthyroidism features decreased TSH and normal T3 and T4 levels

17. Autoantibody tests for hyperthyroidism include the following: Anti–thyroid peroxidase (anti-TPO) antibody - Elevation with autoimmune thyroid disease found in 85% of Graves patients. Autoantibody titers in hyperthyroidism and thyrotoxicosis are as follows: Graves disease - Significantly elevated anti-TPO, elevated TSI antibody (TSI ab) Toxic multinodular goiter - Low or absent anti-TPO and negative TSI ab Toxic adenoma - Low or absent anti-TPO and negative TSI ab Patients without active thyroid disease may have mildly positive anti-TPO and TSI ab Subacute thyroiditis - Low or absent anti-TPO and negative TSI

18. Treatment Oral rehydration for dehydrated patients Beta blockers for relief of neurologic and cardiovascular symptoms A non-selective beta blocker such as propranolol is preferred for control of neurologic symptoms, due to its penetration across the blood-brain barrier The beta-blocker dose is typically higher than one would normally need in a patient, because its catabolism is accelerated in hyperthyroidism For mild ophthalmopathy in the form of dry eyes, saline eye drops (acting as tear drops or astringents) may be used as needed, and tight-fitting sunglasses are recommended for outdoors In patients with significant ophthalmopathy and stare, in which they may not be able to close their eyes during sleep, use of an eye patch at night is recommended to prevent corneal abrasion For vision-threatening ophthalmopathy, high-dose glucocorticoids, with consideration of orbital decompression surgery, ocular radiation therapy, or a recently approved treatment from the US Food and Drug Administration (FDA), teprotumumab-trbw, a monoclonal antibody that blocks the insulin-like growth factor-1 receptor (IGF-1R) and ameliorates proptosis by reducing inflammation and preventing muscle and fat-tissue remodeling in the orbit

19. In adult men and nonpregnant women, used to control hyperthyroidism, for a so-called "cooling-down effect," before definitive therapy with radioactive iodine Methimazole is more potent and longer-acting than propylthiouracil Propylthiouracil is reserved for use in thyroid storm, first trimester of pregnancy, and methimazole allergy or intolerance Propylthiouracil reduces conversion of T4 to T3, hence giving it an advantage over methimazole in thyroid storm Antithyroid drug doses are titrated every 4 weeks until thyroid functions normalize Patients with Graves disease may experience remission after treatment for 12-18 months, but recurrences are common within the following year Toxic multinodular goiter and toxic adenoma will not go into remission

20. Radioactive iodine therapy Preferred therapy for hyperthyroidism Administered orally as a single dose in capsule or liquid form Causes fibrosis and destruction of the thyroid over weeks to many months Hypothyroidism is a common outcome Pregnancy, breast feeding, and recent lactation are contraindications Radioactive iodine should be avoided in children younger than 5 years  [ 4 ] Radioactive iodine is usually not given to patients with severe ophthalmopathy, because thyroid antigen, suddenly released as a result of destruction of the thyroid gland, interacts with receptors in orbital tissues and can aggravate ophthalmopathy Radioactive iodine is usually not given to patients who cannot comply with physician restrictions for avoidance of radiation exposure to others

21. Thyroidectomy Severe hyperthyroidism in children Pregnant women who are noncompliant with or intolerant of antithyroid medication Patients with very large goiters or severe ophthalmopathy Patients who refuse radioactive iodine therapy Refractory amiodarone-induced hyperthyroidism Patients who require normalization of thyroid functions quickly, such as pregnant women, women who desire pregnancy in the next 6 months, or patients with unstable cardiac conditions

22. Thank you!!