NUCLEAR ENDOCRINOLOGY Thyroid BY Ahmed Ramadan assistant lecturer clinical oncology & Nuclear medicine dep. Mansoura university

THYROID Nuclear medicine Diagnostic: In-vitro thyroid function tests: serum T3, T4, FT3*, FT4,TSH, Tg, TgAb. In-vivo thyroid function tests : RAI uptake, Thyroid scan, I-131 WBS. Therapeutic: Hyperthyroidism Differentiated thyroid cancer (DTC)

ANATOMY 2 lobes connected with “isthmus” Anterior to 2nd-4th tracheal rings- C5-T1 vertebrae Thyroid tends to increase weight with age (N=20g) Arteries: Superior, inferior thyroid A. Veins: Superior, middle, & inferior thyroid V.

Histology Follicular cells (F-cells): secrete hormones T3 (triidothyronine) T4 (thyroxine) Parafollicular cells (C-cells): secrete hormone Calcitonin

Hypothalamic-Pituitary-Thyroid Axis Physiology Hypothalamic-Pituitary-Thyroid Axis HYPO-THALAMUS TRH PITUITAY GLAND TSH THYROIDGLAND T3 & T4 Feedback

Thyroid Hormone Synthesis Physiology Thyroid Hormone Synthesis Iodide trapping: into follicular cells Organification : Tyrosine + I- inactive iodotyrosines: 3-monoiodotyrosine (MIT) & 3,5- diido tyrosine (DIT) incorporated into Tg & stored as colloid. Coupling : MIT + DIT T3 DIT + DIT T4 Proteolysis or release : proteolysis of Tg produces the active hormones T3 & T4, then secreted into the blood. Peroxidase

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: To determine the amount of thyroid tissue left after surgery. To detect thyroid metastases associated with thyroid cancer, To show the comparative function of different parts of the glands, 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

Indications (Anatomical &Functional) 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 T4 at least 2 wks. Radiopharmaceuticals: Tc-99m Pertechnetate 0.5-4.0 mCi 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 Solitary Hot Nodule: Hyperfunctioning adenoma(s) Ant RAO Solitary Hot Nodule: Hyperfunctioning adenoma(s) Anatomical variant Thyroid carcinoma Compensatory hypertrophy

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

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

Diffuse toxic goiter (Graves’ Disease)

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

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

Subacute Thyroiditis Diffuse homogenous symmetrical decreased uptake.

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

Ectopic thyroid Sublingual thyroid

Whole body iodine Scan Indications 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 (T4) 4-6 wks prior to WBS, TSH > 30 mIU/L Radiopharmaceutical: Diagnostic dose of I-131: 2-5 mCi 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

Metastatic thyroid cancer

Metastatic thyroid cancer

Thank you