This document summarizes thyroid pathophysiology and scintigraphy findings. It discusses: I. Goiter which can be present in hypo-, hyper-, or euthyroid states. II. Hyperthyroidism, including Graves' disease, toxic adenoma, and toxic multinodular goiter. III. Hypothyroidism. IV. Thyroiditis such as Hashimoto's thyroiditis. V. Thyroid carcinoma including papillary, follicular, medullary, and anaplastic types. It also describes abnormal scintigraphy findings including ectopic thyroid tissue, hot/cold nodules, multinodular goiter, diffuse toxic goiter, thyroiditis, and metastasis of

1. THYROID PATHOPHYSIOLOGY
SCINTIGRAPHY
NMT631

2. 2
THYROID PATHOPHYSIOLOGY
I. Goiter
II. Hyperthyroidism
a. Graves’ Disease
b. Toxic adenoma
c. Toxic multinodular goiter
III. Hypothyroidism
IV. Thyroiditis
V. Thyroid carcinoma

3. 3
I. Goiter:
• enlarged thyroid gland
– May be present in hypo-, hyper-, and euthyroid
states

4. I. Goiter:
– Physiological goiter: enlargement due to
increased demand of thyroid hormones (eg:
puberty, pregnancy, etc)
– Simple goiter: results from dietary iodine
deficiency (Low iodine → Low T3/T4 levels
→ ↑ TSH → chronic thyroid excitation &
hyperplasia.
– Excessive goiterogens: eg: cabbage, turnip
& some drugs can suppress T3/T4 levels and
lead to goiter formation
4

5. 5
II. Hyperthyroidism
(thyrotoxicosis)
- All metabolic activities accelerated
Symptoms:
loss of weight
tiredness,
fine tremors,
heat intolerance,
wet/warm skin,
easily excitable,
difficulty sleeping,
menstrual disturbances,
diarrhea and anxiety;
May or may not have goiter or exopthalmia.

6. II. Hyperthyroidism (thyrotoxicosis)
- Different types
a. Graves’ Disease (diffuse toxic
goiter)
b. Toxic adenoma (autonomous
functioning nodule)
c. Toxic multinodular goiter
- Treatment options
Suppressive thyroid medication
Surgery
Radioiodine therapy
6
Patient with hyperthyroidism. A wide-eyed,
staring gaze, caused by overactivity of the
sympathetic nervous system, is one of the
classic features of this disorder. In Graves
disease, one of the most important causes of
hyperthyroidism, accumulation of loose
connective tissue behind the orbits also adds
to the protuberant appearance of the eyes.

7. 7
• autoimmune disease
• accounts for 85% of cases of hyperthyroidism
• Symptoms: goiter, exophthalmos + other hyperthyroid symptoms
Abnormal antibodies that mimic TSH stimulates excess thyroid hormone
production and cause negative feedback for TSH production.
II. Hyperthyroidism-
a. Graves’ Disease
Results in High T3/T4
and low TSH levels
in blood

8. 8
• autonomously
functioning thyroid
nodule
• increased serum levels
of T3 and/or T4 and
suppression of serum
TSH.
• Patient is not
exopthalmous
II. Hyperthyroidism-
b. Toxic adenoma

9. 9
Multiple autonomously functioning
overactive nodules producing excess
thyroid hormones (increased serum
levels of T3 and/or T4 and
suppression of serum TSH)
• 2nd most common cause of
hyperthyroidism
• commonly found in areas of iodine
deficiency and arises from a long-
standing simple goiter
• Patient not exopthalmous and often
seen in the elderly
II. Hyperthyroidism-
c. Toxic multinodular goiter

10. 10
III. Hypothyroidism
- Primary: thyroid gland
failure or congenital
absence
- Secondary:
pituitary/hypothalmic
failure
The rate of metabolism slows causing mental and physical sluggishness.

11. 11
IV. Thyroiditis
• Multiple causes:
- automimmune (Hashimoto’s
disease)
viral or bacterial
• Patient may exhibit symptoms of hyper-
or hypothyroidism depending on stage of
disease

12. IV. Thyroiditis
Hashimoto's disease
(chronic thyroiditis)
- Most common of thyroiditis
- caused by a reaction of the immune system against the thyroid
gland (autoimmune disorder)
- causes hypothyroidism
- most often seen in
middle-aged women
12

13. V. Thyroid carcinoma
Four types:
►Papillary
► Follicular
► Medullary
► Anaplastic
13

14. V. Thyroid carcinoma
Papillary
• about ½ of thyroid cancers
• slow growth
• excellent prognosis if detected early
14

15. V. Thyroid carcinoma
Follicular
• about ¼ of thyroid cancers
• aggressive than papillary
• Prognosis directly related to tumor size [less
than 1.0 cm good prognosis]
15

16. V. Thyroid carcinoma
Medullary
• arises from parafollicular C cells
• good prognosis if restricted to thyroid gland
• poor prognosis if metastasized
16

17. V. Thyroid carcinoma
Anaplastic
• least common type
• Undifferentiated
• poor prognosis
• poor response to therapy
17

18. V. Thyroid carcinoma
Treatment
۞ Treatment for papillary and follicular thyroid
carcinomas consists of thyroidectomy
followed by radioiodine ablation.
۞ Treatment of medullary carcinoma consists
of surgery and for anaplastic carcinoma the
treatment is only palliative.
18

19. V. Thyroid carcinoma
Statistics
19

20. 20
• Ectopic tissue
• Thyroid Nodules
–“Hot” nodules
– “Cold” nodules
– Multinodular gland
• Diffuse toxic goiter
• Thyroiditis
• Thyroid Carcinoma
The Abnormal Scan

21. 21
Ectopic thyroid tissue
The Abnormal Scan
May occur in Neck (lingual thyroid), pelvis or retrosternally in medastinum
A thyroid image showing no functioning thyroid tissue in the neck, but
an area of avid tracer accumulation lying in the midline which
corresponds to the posterior part of the tongue (lingual thyroid)
An Atlas of Clinical Nuclear Medicine
- Ignac Fogelman, Michael Maisey, Susan E. M. Clarke
marker

22. 22
Thyroid Nodules – Hot Nodule
• Increased radionuclide
concentration
• > 99% benign
• May function independent
of thyroid-pituitary axis
feedback mechanism
(autonomous nodules)
The Abnormal Scan
An Atlas of Clinical Nuclear Medicine
- Ignac Fogelman, Michael Maisey, Susan E. M. Clarke
A solitary “toxic” nodule
with suppression of the
reminder of the thyroid

23. 23
Thyroid Nodules – Cold Nodule
• Non-functioning thyroid nodule
• Large majority benign but a small
percentage (15-25%) cancerous
The Abnormal Scan
Pathological diagnosis confirmed
a benign adenoma in the region
of cold spot (arrows)
Cardiothoracic Surgery Network
An Atlas of Clinical Nuclear Medicine
- Ignac Fogelman, Michael Maisey, Susan E. M. Clarke

24. 24
Thyroid Nodules – Multinodular Goiter
(MNG)
• Typically presents as an enlarged thyroid with multiple hot
and/or cold nodules.
The Abnormal Scan
University Hospitals of Cleveland
Multiple cold nodules Multiple hot nodules

25. 25
Diffuse Toxic Goiter
(Graves’ disease)
Characteristic findings:
• Thyromegaly
• Increased activity throughout
the gland
• Frequently w/ pyrimidal lobe
• Increased perfusion and rapid
uptake of tracer
The Abnormal Scan
Pyramidal lobe
BrighamRAD Teaching Case
The intensity of thyroid gland uptake exceeds the uptake in both salivary glands (arrows), background
activity is markedly decreased, and the pyramidal lobe is clearly visible. All of these findings indicate
a hyperfunctioning gland. There is no focal photopenic or focal hot area to suggest a nodule.

26. 26
Chronic Thyroiditis
(Hashimoto’s thyroiditis)
• most common form of
inflammatory disease of the
thyroid
• Scan appearance varies from
‘uniform increased activity’ to
‘markedly depressed’ (sub-
acute thyroiditis) radioiodine
uptake.
• Positive thyroid antibodies
The Abnormal Scan
Sub-acute thyroiditis
MIR teaching file

27. 27
Thyroid Carcinoma
• Usually demonstrated as
cold nodules
• Whole body evaluations
for metastasis done
within 1-2 months of total
or partial thyroidectomy
The Abnormal Scan
Abnormal diffuse activity in lungs, right
neck, mediastinum, mid-abdomen, pelvis,
left thigh, right thigh indicating metastasis
MIR teaching file

28. 28
• Remind the patient not to swallow during imaging
• Contamination
– I-131 and I-123 sodium iodide are excreted in the urine,
saliva, and perspiration; 99mTc-Pertechnetate is excreted
through urine.
– Protect self and equipment
– Take precautions to prevent contamination artifacts on
images
Artifacts & Pitfalls