Thyroid Pathology

Question 1

How much does the thyroid usually weigh?

Answer 1

20g

Question 2

Describe the histology of the normal thyroid

Answer 2

colloid protein is surrounded by epithelial thyroid cells - also contains lots of capillaries, some connective tissue and some C cells

Question 3

What is the origin of C cells?

Answer 3

neuroendocrine

Question 4

Why does the thyroid look very pink on an H&E stain?

Answer 4

because the colloid is filled with thyroglobulin - a protein which stains pink

Question 5

How can you differentiate between an inactive thyroid and an active thyroid histologically?

Answer 5

an inactive thyroid has low cuboidal cells and an active thyroid has tall cuboidal or columnar cells with scalloping of the colloid

Question 6

What is thyrotoxicosis?

Answer 6

elevated circulating T3 and T4 - includes hyperthyroidism but not necessarily hyperthyroidism

Question 7

What is a goitre?

Answer 7

enlargement of the thyroid - may be associated with hyperthyroidism, hypothyroidism or euthyroidism

Question 8

How does a diffuse non toxic ‘simple’ goitre occur?

Answer 8

low circulating thyroid hormones will lead to high TSH which will stimulate growth of the thyroid - usually occurs due to low dietary iodine - due to compensatory response the blood tests will be euthyroid

Question 9

What does a diffuse non toxic simple goitre look like histologically?

Answer 9

follicles will be lined by crowded hyperplastic cells, follicles of irregular size

Question 10

How does a simple goitre become multinodular?

Answer 10

over time with cycles of hyperplasia the follicles will either become large and nodular or will rupture and fibrose

Question 11

How can a multinodular goitre lead to hyperthyroidism?

Answer 11

if the nodules become autonomous and over produce thyroid hormones

Question 12

What is Pemberton’s sign and what causes it?

Answer 12

raising arms above head and face goes red - caused by an enlarged thyroid compressing on the venous system and causes venous congestion

Question 13

What does the thyroid look like histologically in Hashimoto’s?

Answer 13

mononuclear inflammatory infiltrate (lymphocytes, plasma cells, germinal centres), thyroid cells with abundant, granular, eosinophilic cytoplasm and increased interstitial connective tissue with fibrosis and scarring

Question 14

What does the gross pathology of a thyroid in Hashimoto’s look like?

Answer 14

a pale, small, nodular thyroid

Question 15

What is the pathophysiology of Hashimoto’s?

Answer 15

breakdown of tolerance to thyroid tissues causes damage by CD8 mediated cell death, cytokine mediated cell death, antibody mediated cell mediated cytotoxicity and antibodies block TSH

Question 16

What are the clinical features of Hashimoto’s?

Answer 16

hypothyroidism, goitre, anti-TG and anti-TPO antibodies, high TSH, low fT4

Question 17

What are the 3 clinical features of Grave’s disease?

Answer 17

hyperthyroidism, opthalmopathy, pretibial myxoedema

Question 18

What does the thyroid look like histologically in Grave’s disease?

Answer 18

follicular cells are tall and crowded, scalloping of colloid, paler staining colloid, lymphocytic infiltrate

Question 19

What is the gross pathology of a thyroid in Grave’s disease?

Answer 19

diffuse symmetrical enlargement that is soft

Question 20

What antibodies are present in Grave’s disease and what is their effect on the TSH receptor?

Answer 20

thyroid stimulating immunoglobulin which stimulates the TSH receptor, thyroid growth stimulating immunoglobulin which stimulates the TSH receptor and TSH-binding inhibitor immunoglobulins which stimulate or inhibit the TSH receptor

Question 21

What causes the opthalmopathy in Grave’s disease?

Answer 21

the fibroblasts behind the eye express a TSH-like antigen and produce more hyaluronic acid and transform into adipocytes

Question 22

What type of hypersensitivity is Grave’s disease?

Answer 22

type II

Question 23

What type of hypersensitivity is Hashimoto’s?

Answer 23

type IV