2: Pathology of the thyroid gland Flashcards
At what level is the thyroid gland found?
C5 - T1
Where does the thyroid gland start out during development?
Through which hole in the tongue does it move inferiorly?
Which passage carries it to the neck?
Tongue
Foramen caecum
Thyroglossal duct
What is a thyroid called when it fails to descend through the thyroglossal duct?
Lingual thyroid
If the thyroid gland descends too much during development, where can it end up?
Mediastinum
behind the sternum
What is a thyroglossal duct cyst?
Benign growth which moves with swallowing
The thyroid gland is an endocrine organ composed of ___, where the thyroid hormones are produced.
follicles
What chemical is found in thyroid follicles?
Thyroglobulin
Which cells produce T3 and T4?
Follicular cells
Which cells are found next to follicles and secrete calcitonin?
C cells (parafollicular cells)
hypothalamus
trh
anterior pituitary
tsh
thyroid gland
t3 and t4
target cells
When T3 / 4 levels are high, the secretion of hormones along the h.p.t axis is (increased / suppressed).
suppressed
What type of receptor are TSH receptors?
G protein receptors
Release of T3 and T4 are controlled by cyclic AMP
What do the thyroid hormones do?
Regulate metabolic rate
What happens to the size of the thyroid gland when it is
a) hyperactive
b) underactive?
hyperactive - enlarged
underactive - atrophied
What is thyroiditis?
Inflammation of the thyroid gland
Which type of thyroiditis causes hypofunction?
Hashimoto’s
What kind of thyroiditis causes hyperfunction?
Graves disease
Hashimoto’s disease causes ___thyroidism.
hypothyroidism
Graves disease causes ___thyroidism.
Why?
hyperthyroidism
Disease stimulates thyroid gland
Autoimmune thyroiditis has a large ___ component.
genetic
What are some genes associated with autoimmune thyroiditis?
CTLA-4
PTPN-22
What state occurs as a result of excess thyroid hormone in hyperthyroidism?
Thyrotoxicosis
Apart from hyperthyroidism, what else can cause thyrotoxicosis?
Thyroiditis
Ectopic thyroid gland
What is the most common cause of hyperthyroidism?
Graves disease
Apart from Graves disease, hyperthyroidism can also be caused by ___.
tumours
of both thyroid and other organs e.g pituitary
Graves disease is more common in (men / women).
women
What antibody is associated with Graves disease?
TSH receptor antibodies
What are the three main features seen in Graves disease?
Hyperthyroidism
Eye changes
Pretibial myoxedema (leg swelling)
What is the main cause of hypothyroidism?
Hashimoto’s thyroiditis
As with Graves and other thyroid diseases, Hashimoto’s thyroiditis mainly affects ___.
women
What are some other causes of hypothyroidism apart from Hashimoto’s?
Iodine deficiency
Drugs
Congenital
Tumours
Hashimoto’s thyroiditis involves a (sudden / gradual) change in thyroid function.
gradual failure
Which autoantibodies are raised in Hashimoto’s thyroiditis?
Anti-PTO antibodies (main ones)
Anti-thyroglobulin
Which cells are responsible for autoimmune destruction of the thyroid gland in Hashimoto’s thyroiditis?
T lymphocytes
Why are autoimmune thyroid conditions sometimes paradoxical?
Often there are short periods of HYPO in Graves and HYPER in Hashimoto’s
What cancer are people with Hashimoto’s thyroiditis at risk of?
Non-Hodgkins lymphoma of thyroid
What is a goitre?
Enlargement of thyroid gland
What commonly causes goitre?
Iodine deficiency
How do goitres occur in terms of iodine deficiency?
Reduced T3 / T4 production
Increased levels of TSH
Thyroid enlargement
Goitre is commonly associated with (hypo / hyperthyroidism).
hypothyroidism
What types of benign neoplasm can arise in the thyroid gland?
Adenomas - glandular tumours
Adenomas of the thyroid are derived from the ____ epithelium.
follicular
What type of malignant neoplasm arises in the thyroid?
Carcinomas
papillary
follicular
medullary - from c cells
anaplastic - wild, poor prognosis
What do thyroid adenomas look like?
Discrete
Solid
Benign thyroid adenomas are surrounded by a thick sheet of ___ which is well circumscribed.
collagen
Do thyroid adenomas function like normal thyroid tissue?
Usually non-functional
Are thyroid carcinomas common?
No
1.5% of all cancers
Most thyroid carcinomas come from the follicular epithelium.
Where do medullary carcinomas come from?
C cells
What is the most common type of thyroid carcinoma?
Papillary carcinoma
What are some associations with
a) papillary carcinoma
b) follicular carcinoma?
a) Ionising radiation e.g Chernobyl disaster
b) Iodine deficiency
Papillary carcinomas commonly spread through which system?
What may you find on general examination?
Lymphatic system
Enlarged lymph nodes
What symptoms do papillary carcinomas cause when enlarged?
Hoarseness
Dysphagia
Cough
Dyspnoea
Onset of symptoms suggest a (basic / advanced) papillary carcinoma.
advanced
Papillary carcinomas usually have a (good / bad) prognosis.
Good
95% live beyond 10 years
What is the second most common thyroid cancer?
Follicular carcinoma
Do follicular carinomas spread via the lymphatic system?
No, via bloodstream
Which type of thyroid carcinoma is derived from C cells?
Medullary carcinoma
What type of thyroid tumour is extremely aggressive and is least common?
Anaplastic carcinoma
What is the mortality of anaplastic carcinoma?
100%