NUCLEAR ENDOCRINOLOGY THYROID BY AHMED RAMADAN ASSISTANT LECTURER

NUCLEAR ENDOCRINOLOGY THYROID BY AHMED RAMADAN ASSISTANT LECTURER CLINICAL ONCOLOGY & NUCLEAR MEDICINE DEP. MANSOURA UNIVERSITY

THYROID Nuclear medicine Ø Diagnostic: In-vitro thyroid function tests: serum T 3, T 4, FT 3*, FT 4, TSH, Tg. Ab. § In-vivo thyroid function tests : RAI uptake, Thyroid scan, I-131 WBS. Ø Therapeutic: § Hyperthyroidism § Differentiated thyroid cancer (DTC) §

ANATOMY � 2 lobes connected with “isthmus” � Anterior to 2 nd-4 th tracheal rings- C 5 -T 1 vertebrae � Thyroid tends to increase weight with age (N=20 g) � Arteries: Superior, inferior thyroid A. � Veins: Superior, middle, & inferior thyroid V.

Histology Follicular cells (F-cells): secrete hormones § T 3 (triidothyronine) § T 4 (thyroxine) � � Parafollicular cells (C-cells): secrete hormone Calcitonin

Physiology Hypothalamic-Pituitary-Thyroid Axis TSH • HYPOTHALAMU S TRH • PITUITAY GLAND • THYROIDG LAND T 3 & T 4 Feedback

Physiology � � � § § � Thyroid Hormone Synthesis Iodide trapping: into follicular cells Peroxidase Organification : Tyrosine + I inactive iodotyrosines: 3 -monoiodotyrosine (MIT) & 3, 5 - diido tyrosine (DIT) incorporated into Tg & stored as colloid. Coupling : MIT + DIT T 3 DIT + DIT T 4 Proteolysis or release : proteolysis of Tg produces the active hormones T 3 & T 4, then secreted into the blood.

Factor interfering with RAI uptake � Iodine load: § Iodide-containing drugs eg. Amiodarone, KI in cough remedy, Betadine § Previous contrast studies eg. CT, IVP 4 -6 wks. § Sea food or iodine-containing food/supplements � Thyroid hormone medications > 2 wks. � Antithyroid drug > 1 wk.

THYROID SCINTIGRAPHY Imaging of thyroid can be useful for the following purposes: I. To determine the amount of thyroid tissue left after surgery. II. To detect thyroid metastases associated with thyroid cancer, III. To show the comparative function of different parts of the glands, IV. To measure the size and position of the thyroid prior to surgery or other treatments of the disease.

Common Thyroid Disorders � � � § § § � Thyroid nodules: Solitary vs multiple Hypothyroidism: Congenital & acquired Hyperthyroidism: Graves’ disease. Toxic adenoma. Multinodular toxic goiter. Thyroiditis: Acute. Subacute. Chronic Hashimoto’s thyroiditis. Thyroid Cancer: DTC, MTC, Others

THYROID SCINTIGRAPHY THYROID SCAN WHOLE BODY IODINE SCAN

Thyroid Scan Indications (Anatomical &Functional) � Evaluation of thyroid nodules : No. & type � Evaluation of congenital hypothyroidism : Agenesis. � Evaluation of neck masses : ectopic thyroid, thyroglossal cyst. � Evaluation of thyrotoxicosis.

Thyroid Scan Technique: � Preparation: No T 4 at least 2 wks. � Radiopharmaceuticals: § Tc-99 m Pertechnetate 0. 5 -4. 0 m. Ci iv. § I-123 50 - 100 µCi orally. � Equipment: Gamma camera with pinhole collimator ( Ant. , Ant. with mark, RAO, LAO) � Procedure: Static imaging at 20 min or 6 -24 hr respectively.

Normal Thyroid Scan Homogenous radioactive tracer distribution throughout thyroid & salivary glands. � No retrosternal extension. � Normal symmetrical uptake: (0. 4 -4. 0 %) �

Normal Thyroid Scan

Thyroid Nodule Solitary Cold Nodule: � Colloidal cyst � Hypofunctioning adenoma � Thyroid carcinoma � Others : focal thyroiditis, abscess, hematoma, lymphoma, metastasis, parathyroid adenoma, lymph node enlargement

Thyroid Nodule Ant n n Solitary Hot Nodule: Hyperfunctioning adenoma(s( Anatomical variant Thyroid carcinoma Compensatory hypertrophy RAO

Diffuse Simple goiter Enlarged both thyroid lobes. Ø Diffuse normal homogenous uptake of radioactive tracer. Ø

Diffuse toxic goiter (Graves’ Disease) Enlarged both thyroid lobes. Ø Diffuse increased homogenous uptake of radioactive tracer. Ø May be retrosternal extension Ø

Diffuse toxic goiter (Graves’ Disease)

Nodular toxic goiter (Plummer’s disease) Enlarged one or both thyroid lobes. Ø Heterogeneous distribution with multiple areas of increased radioactive tracer. Ø May be retrosternal extension Ø

multi. Nodular goiter Enlarged one or both thyroid lobes. Ø Heterogeneous distribution radioactive tracer. Ø May be retrosternal extension Ø

Subacute Thyroiditis Diffuse homogenous symmetrical decreased uptake.

Absent thyroid uptake Congenital agenesis. Ø Ectopic thyroid. Ø Surgically removed. Ø

Ectopic thyroid Sublingual thyroid

Whole body iodine Scan Indications ü ü ü Post-operative evaluation for thyroid remnant or functioning metastasis Follow up patients after I-131 ablation or I-131 treatment Rising Serum Tg. Suspected tumor recurrence Suspected functioning metastases , either local or distant metastases

Whole body iodine Scan Technique: Patient preparation: Withdraw thyroid H (T 4) 4 -6 wks prior to WBS, TSH > 30 m. IU/L Radiopharmaceutical: Diagnostic dose of I 131: 2 -5 m. Ci orally given. Equipment: Gamma camera with parallel hole high energy collimator Procedure: Anterior and posterior whole-body imaging at 72 hrs later. WBS can also performed after 3 -7 d of RAI Rx dose

Normal Whole body iodine Scan

Normal Whole body iodine Scan Tissues that often take up iodine and can be misinterpreted as metastases include the following: �salivary glands in the mouth, �esophagus (as a result of swallowing radioactive saliva), �thymus gland, �breasts in some women, �liver, stomach, colon, bladder

Residual thyroid tissue

Metastatic thyroid cancer

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