Pathology of the thyroid gland Flashcards
What does the thyroid gland develop from embryologically?
an evagination of pharnygeal epithelium
What causes inlgual thyroid?
failure of descne of thyroid from tongue
How do you tell a thyroglossal duct cyst?
will move on swallowing; in the midline of the neck
What type of cells surrounds each follicle?
flat to cuboidla follicaular epithelial cells
What does TSH bind to in the thyroid?
TSH receptor on surface of thyroid epithelial cells
How does binding to the TSH receptor induce release of T3 and T4?
G proteins stimulate production of cAMP which increases production and release of T3 and T4
What do T3 and T4 bind to the nucleus?
thyroid response elements
Aside from Grave’s, what else can cause hyperthyroidism?
hyperfunctioning nodules/ tumours, thyroiditis; TSH secreting pituitary adenoma; ectopic production (struma ovarii); factitious (exogenous intake)
What are the 2 autoimmune diseases affecting the thyroid gland?
Hashimoto’s thyroiditis and Grave’s disease
What are antibodies produced against in Grave’s disease?
TSH receptor; thyroid peroxisomes; thyroglobulin
What are the types of anti-TSH receptor antibody in Grave’s disease?
thyroid stimulaating immunoglobulin; thyroid growth stimulating immunoglobulin; TSH biding inhibitor immunoglobulin
What is the most specific Ab for Grave’s?
thyroid stimulating immunoglobulin
What might the presesnce of TSH binding inhibitor immunoglobulin hlpe explain?
episodes of hypofunction
What are the triad of features seen with Grave’s disease?
hyperthyroidisim with diffuse enlargement of the thyroid; eye changes; pretibial myxoedema
What do the eye changes in Grave’s result from?
fibroblasts etc. expressing TSH receptors
What are the antibodies found in Hashimoto’s thyroiditis?
anti-thyroglobulin and anti-peroxidase
What is the difference in antibodies in Hashimoto’s and Grave’s and why does this cause differences in clinical picture?
the main antibody in Grave’s is anti-TSH receptor antibody, which stimulates the receptor to produce more T3 and T4 but is not affected by the feedbakc loop. In Hashimoto’s, the main antibodies are made against thyroglobulin- a precursor of T3 and T4 and peroxidase- an ezyme used to make T3 and T4
What is Hashitoxicosis?
transient hyperfunction before decrease in function in Hashimoto’s
What are pts with Hashimoto’s more at risk of developing in the thyroid?
B cell NHL (lymphoma)
What causes diffuse goitre?
reduced T3/T4 production causes rise in TSH stimulating gland enlargement to maintain euthyroid state
What can cause diffuse goitre?
ingestion of substances limiting T3/T4 production; inborn errors of metabolism (dyshormonogenesis)
What is seen on blood tests in patients with diffuse goitre?
T3/T4 normal but TSH high or upper limit of normal
What do patients usually present with with diffuse goitre?
mass effects (usually euthyroid)
What can dyshormonogenesis lead to in children?
cretinism
What does multi-nodular goitre develop from?
long-standing simple goitre- recurrent hyperplasia and involution
What should you suspect in patients with multi-nodular goitre?
thyroid neoplasm
Why can people with multi-nodular goitre develop hyperthyroidism?
may develop an autonomous nodule
What is the type of adenoma seen with thyroids?
follicular adenoma
What types of carcinoma are seen in the thyroid?
papillary; follicular; medullary; anaplastic
What are the features of a follicular adenoma?
discrete solitary mass; encapsulated by a surroudning collagen cuff; compaosed of neoplastic thyroid follicles
What can an adenoma be difficult to distinguish from?
dominant nodule in multinodular goitre; follicular carcinoma
Are thyroid carcinomas more common in females or males?
females
What age group gets thyroid carcinoma?
early adulthood
What type of carcinoma is associated with ionising radiation?
papillary carcinoma
What type of carcinoma is associated with iodine deficiency?
follicular carcinoma
What is the most common form of thyroid cancer?
papillary carcinoma
How does papillary carcinoma usually present?
solitary nodule- can be mulitofcal; often cystic; may be calcified- Psammoma bodies on biopsy
What is the difference between the spread of papillary and follicular carcinoma?
papillary goes through lymph whereas follicular tends to spread haematogenously
How do you distinguish between follicular carcinoma and adenoma?
carcinoma will have vascular or capsular invasion
What cells are medullary thyroid carcinomas derived from?
c-cells
What does amyloid represent?
deposition of an abnormally folded protein
What is anaplastic carcinoma?
undifferentiated and aggressive tumours- may arise in patients with a Hx of differentiated thyroid chancer whic hhas then dedifferentiated
How many parathyroid glands do most people have?
4
What type of cells are parathyroid glands composed of?
chief cells
How do chief cells appear?
roudn cells with moderate cytoplasm and bland roudn central nuclei
What type of cell suppports the chief cells in the parathyroid?
oxyphil cells
What type of cytoplams do oxyphil cells have?
acidophilic
What does PTH do?
acts on calcium homeostasis
What does hyperparathyroidism normally result from?
small adenomas
What else can causes hyperparathyroidism?
hyperplasia; carcinoma
What is the difference between an adenoma nad hyperplasia in the parathyroid glands?
adenoma is a single gland involved but hyperplasia typically involves all the glands
What causes secondary hyperparathyroidism?
chronic hypocalcaemia
What is tertiary hyperparathyroidism?
when parathyroid activity becomes autonomous - hypercalcaemia
What are the consequences of hyperparathyroidism?
bone disease; nephrolithiasis; GI complications- constipation; nausea; peptic ulcer disease; pancreatitis; glla stones; CNS- depression; lethargy; seizures; calcification of aortic and mitral valves; wekaness anf fatigue
What congenital problem can cause hypoparathyroidism?
diGeorge syndrom
What is seen with hypoparathyroidism?
tetany; altered mental state; parkinsonism; calcification of lens and cataract formation; prolonged QT interval in ECG
