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

2. 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)

3. 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.

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

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

6. 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

7. 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.

8. 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.

9. 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

10. THYROID SCINTIGRAPHY
THYROID SCAN
WHOLE BODY IODINE SCAN

11. 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.

12. Thyroid Scan Technique: Preparation: No T4 at least 2 wks.
Radiopharmaceuticals:
Tc-99m Pertechnetate mCi iv.
I 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.

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

14. Normal Thyroid Scan

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

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

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

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

19. Diffuse toxic goiter (Graves’ Disease)

20. 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

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

22. Subacute Thyroiditis
Diffuse homogenous symmetrical decreased uptake.

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

24. Ectopic thyroid
Sublingual thyroid

25. 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

26. 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

27. Normal Whole body iodine Scan

28. 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

29. Residual thyroid tissue

30. Metastatic thyroid cancer

31. Metastatic thyroid cancer

32. Metastatic thyroid cancer

33. Thank you