Thyroid pathology

Question 1

Why are biopsies not usually performed on the thyroid gland?

What is the alternative?

Answer 1

Thyroid gland is very vascular

Do FNA instead

Question 2

Describe the normal appearance of the thyroid gland?

Answer 2

Fleshy, mahogany coloured

Question 3

Describe the origin of the cells of the thyroid gland?

Answer 3

C cells are neuroendocrine in origin

Rest are of epithelial origin

Question 4

Describe the normal histology of the thyroid gland?

Answer 4

Round/oval follicles, various sizes

Epithelial cells line follicles

Follicles filled with colloid

Thin, fibrous septa with rich vascular supply

C cells (difficult to distinguish in H&E)

Question 5

Describe the different histological appearance of inactive and active thyroid follicles?

Answer 5

Inactive: low cuboidal cells, follicle filled with colloid

Active: tall cuboidal/columnar cells, scalloping of colloid (cells taking up colloid)

Question 6

Describe the metabolic symptoms of hypothyroidism?

Answer 6

Hypometabolic state:

cold intolerance

alopecia

cold, thickened skin

weight gain

fatigue

Question 7

Describe the effects of hypothyroidism on the nervous system and the consequences of this?

Answer 7

Sympathetic nervous system underactivity > bradycardia, angina, slow reflexes, constipation, decreased mood and concentration

Question 8

Which population is most affected by hypothyroidism?

Answer 8

Children

Question 9

What are the most common causes of hypothyroidism?

Answer 9

Iodine deficiency

Hashimoto’s disease

Question 10

What is thyrotoxicosis?

Answer 10

Elevated circulating fT3 and fT4

Includes hyperthyroidism

Question 11

Describe the metabolic effects of hyperthyroidism?

Answer 11

Hypermetabolic state:

heat intolerance

warm, flushed skin

fatigue

weight loss

osteoporosis

Question 12

Describe the effects of hyperthyroidism on the nervous system, and the consequences of this?

Answer 12

Sympathetic nervous system overactivity > palpitations, AF, cardiomegaly, tremor, anxiety, insomnia, diarrhoea

Question 13

What are the major causes of thyrotoxicosis?

Answer 13

Graves disease

Hyperfunctioning toxic multinodular goiter

Question 14

Describe the cause of a simple goiter?

Answer 14

Impaired synthesis of thyroid hormone > TSH elevation > thyroid growth stimulated

Question 15

Describe the thyroid hormone levels in a simple goiter?

Answer 15

Usually euthyroid, with slightly high TSH

Question 16

What is the most common cause of simple goiter?

Answer 16

Iodine deficiency

Question 17

Describe the histological appearrance of a simple goiter?

Answer 17

Hyperplasia

Crowded cells line follicles

Some follicles largr than others

Large colloid-filled cysts may be present

Question 18

Describe what happens to the thyroid follicles in a simple goiter with:

a) TSH resolution
b) TSH persistence

Answer 18

a) Follicles incolute
b) Follicles rupture, haemorrhage or grow larger

Question 19

Describe what can happen to a simple goiter over time?

Answer 19

Cycles of hyperplasia and involution > follicles can become large nodules > multinodular goiter

Question 20

What can multinodular goiter progress to?

What are the consequences of this?

Answer 20

Nodules can be autonomous (secrete thyroid hormone without TSH) > toxic multinodular goiter

Patient may become hyperhtyroid

Question 21

What is Pemberton’s sign?

When does it occur?

Answer 21

Enlarged thyroid > compresses SVC when arms raised > blood backlog in SVC

Question 22

Describe the histological appearrance of Hashimoto’s thyroiditis?

Answer 22

Mononuclear inflammatory infiltrate: lymphocytes, plasma cells, germinal centres

Hurthle cells: thyroid cells with abundant, eosinophilic, granular cytoplasm

Increased interstitial connective tissue: fibrosis/scarring

Question 23

Describe the gross pathology of Hashimoto’s thyroiditis?

Answer 23

Enlatge at first > atrophic

Cut surface: firm, tan-yellow, pale, nodular

Question 24

Describe the cause of Hashimoto’s thyroiditis?

Answer 24

Breakdown of tolerance to thyroid tissues

Damage by: CD8 cytotoxic cell-mediated death, cytokine-mediated cell death, TSH-blocking Abs

Question 25

Which population is most affected by Hashimoto's thyroiditis?

Answer 25

Females 45-65 yo

Question 26

Describe the clinical presentation of Hashimoto's thyroiditis?

Answer 26

Hypothyroidism Goiter High Anti-g Abs Very high Anti-TPO High TSH, low fT4

Question 27

Describe the triad of clinical findings in Graves disease?

Answer 27

1) Hyperhtyroidism due to diffuse, hyperfunctional enlargement of the thyroid 2) Infiltrative opthalmopathy \> exopthalmos 3) Localised infiltrative dermopathy (pretibial myxoedoma)

Question 28

What is the cause of Graves disease?

Answer 28

Stimulatory auto-Ab to TSH receptor

Question 29

Describe the histological appearance of Graves disease?

Answer 29

Tall, crowded follicular cells \> papillae Diffuse hypertrophy and hyperplasia Widespread scalloping Lymphocytic infiltrates

Question 30

Describe the gross pathology of Graves disease?

Answer 30

Diffuse symmetrical enlargement of thyroid Soft, meaty cut surface

Question 31

Name the auto-Abs that stimulate the TSH receptor in Graves disease?

Answer 31

Thyroid stimulating immunoglobulins (TSI)

Question 32

Which population is most susceptible to Graves disease?

Answer 32

Females 20-50 yo

Question 33

Describe the blood findings in a Graves disease patient?

Answer 33

Low TSH, high fT4 High Anti TPO Abs High TSI

Question 34

Describe what causes the opthalmopathy seen in Graves disease?

Answer 34

Retro-orbital hydrophilic mucopolysaccharides, oedema, lymphocytes, fibrosis and fat Fibroblasts are target and effector cells

Question 35

How can the symptoms of Graves disease be managed?

Answer 35

Beta blocker to reduce sympathetic overactivity

Question 36

Which type of hypersensitivites are Hashimoto's thyroiditis and Grave's disease?

Answer 36

Hashimoto's: T-cell mediated \> Type IV Graves: B-cell mediated \> Type II

Question 37

Describe the thyroid hormone levels in a patient with simple goiter?

Answer 37

Euthyroid