Week 3 - C - Week 3 - Thyroid gland pathology Flashcards
What is the weight of the thyroid gland?
25-30g
What is the evagination from which the thyroid gland develops and how does it travel to the anterior neck?
The thyroid gland develops from an evagination of the developing pharyngeal epithelium that descends as part of the thyroglossal duct from the foramen cecum at the base of the tongue to its normal position in the anterior neck.
When the thyroid gland fails to fully descend, and ectopic thyroid tissue arises at the base of the tongue, what is this known as?
Lingual thyroid
Does lingual thyroid normally require treatment? What is a disadvantage of surgery?
Does not normally require treatment and surgery can render the patient hypothyoird
What are the round structures containing the thyroglobulin containing colloid?
Follicles
What are the cells located within the follicle known as?
follicular cells
What are the cells located in the thyroid which secrete calctionin? What does an increase in calcitonin caus?
These are the parafollicular cells (C cells)
Calcitonin causes a decrease in blood calcium levels
How does parathyroid hormone increase blood calcium level from bone? vs How does calcitonin decrease blood calcium levels from bone?
PTH increase osteoclast activity leading to breakdown of bone and calcium release into the blood
Calcitonin lowers blood calcium levels by suppressing osteoclast activity in the bones and increasing the amount of calcium excreted in the urine
What are the large purple objects? What are the small dark purple cells? What are the cells that are intermediate size?
Large purple are colloid Follicular cells Parafollicular cells (C cells)
What is the release of hormones from hypothalamus to thyroid?
Thyrotropin releasing hromone (TPH) is released from the hypothalamus stimulating the release of thyroid stimulating hormone (TSH) from anterior pituitary which when acting on the follicular cell causes the release of T3 and T4 into the bloodstream
Tropic hormones are hormones that have other endocrine glands as their target. Name at least 2 of the four tropic hormones of the anterior pituitary gland?
follicle-stimulating hormone (FSH) luteinizing hormone (LH), adrenocorticotropic hormone (ACTH) and thyroid-stimulating hormone (TSH).
TSH binds to TSH receptor on surface of thyroid epithelial cell (follicular cell), how does this binding cause the release of T3 and T4?
The binding of TSH cause the activation of Gproteins converting GTP to GDP and the production of cAMP cAMP increases the production and release of T3 and T4
What is 85% of hyperthyroidism due to?
85% due to Grave’s disease
What are two potential other causes of hyperthyroidism? (one is to do with ovaries)
TSH secreting pituitary adenoma Struma ovarii - a rare ovarian tumour which may cause hyperthyroidism (contains mostly throid tissue)
Polymorphisms in immune regulation associated genes can cause an under/over active thyroid Polymporphisms in what two genes can make you more susceptible to thyroid dysnfunction? (the two genes appear to be involved in many autoimmune conditions according to articles online)
CTLA4 gene and PtPN22 gene
If the patient has hyperthyroidism symptoms and is above or below 40, what do you think?
Below 40 - grave’s disease Above 40- multi-nodular goitre
What is the main group of antibodies in grave’s disease known as?
Anti-TSH receptor antibodies (anti-Trabs)
What are the three anti-TSH antibodies? Which can cause hypothyroidism?
Thyroid stimulating immunoglobulin Thyroid growth stimulating immunoglobulin TSH binding inhibitory immunoglobulin - this can cause hypothyroidism as it blocks the binding of TSH
What is the triad of features in graves’ disease?
Hyperthyroidism - diffuse enlargement of the thyroid gland Exopthalmos Preitibial myxoedema
What are the majority of cases of hypothyroidism due to?
Hashimoto’s thyroditis
What are the haplotypes associated with ashimoto’s thyroditis?
HLA-DR3 and HLA DR5
What are other ways in which you can get hypothyroidism?
Iodine deficiency Iodine excess - needs to be high excess Drugs such as lithium and amiodarone
What are the two common antibodies in hashimoto’s? When bound cause antibody dependent cell mediated cytotoxicity
Anti-TPO(thyroid peroxidase) antibodies Anti- thyroglobulin antibodies The release of the chemical inflammation mediators can cause cell death of the thyroid follicles CD8 +ve cells may mediate destruction of thyroid epithelium
In grave’s can see the lymphoid follicles and the normal follicles
Lymphoid follicles and beginning to lose the thyroid follicles and with it the thyroid hormones
What may hashimoto’s thyroditis be preceded by? (it is a name for the transient hyperfunction)
Hashitoxicosis Hashitoxicosis is a transient hyperthyroidism caused by inflammation associated with Hashimoto’s thyroiditis disturbing the thyroid follicles, resulting in excess release of thyroid hormone.
When having hashimoto’s thyroitis, what lymphoma does this increase your risk of having?
B cell non-hodgkins lymphoma in the affected gland
What is the diffuse enlargement of the thyroid gland known as?
Goitre
What may hypothyroidism in children cause?
Abnormal mental development - cretinism Cretinism is a condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormone (congenital hypothyroidism) usually due to maternal hypothyroidism.
What effects may a multinodular goitre have on eg breathing, GI and vasculature?
May cause dysphagia, stridor and compresson blood vesselsleading to ischaemia of other structures
What do both grave’s and multi-nodular goitre show on scintigraphy?
Grave’s - shows symmetrical uptake of radiation Multi-nodular goitre - asymmetrical uptake
What is the benign tumour of the thyroid gland known as?
Follicular adenoma
What are the 4 types of carcinoma? (in order of most common to least) Which accounts for 80% of the thyroid cancers?
Papillary thyroid carcinoma - accounts for 80% Follicular thyroid carcinoma Medullary thyroid carcinoma - accounts for ~5% Anaplastic thyroid carcinoma
Where do medullary thyroid carcinomas arise?
Arise in parafollicular C cells in the thyroid gland Can measure levels of calcitonin to see an increase which can be indicative of medullary thyroid cancers
Discrete solitary mass encapsulated by a surrounding collagen cuff What is this?
Adenoma
What can an adenoma be difficult to distinguish from?
Difficult to distinguish from dominant nodule in mutli-nodular goitre
What can follicular adenomas secrete to cause thyrotoxicosis?
Can secrete thyroid hormones TSH independent
Mutation inwhat signalling pathways is present in functional adenomas? (functional adenomas - adenomas that secrete thyroid hormones)
Mutation in the TSHR signalling pathway
1.5% all cancers are thyroid cancers Which gender is more commonly affected?
Females are predominantly affected
What type of thyroid cancer does ionising radiation cause? What type does iodine deficiency cause?
Ionising radiation - papillary carcinoma Iodine deficiency - follicular carcinoma
What condition that cause tumours to develop in endocrine glands is medullary thyroid cancer involved in?
Multiple endocrine neoplasia 2 (MEN2)
Mutations in PI3K pathway cause which ype of thyroid cancer?
Follicular carcinoma
What is the most common form of thyroid cancer? Is it usually or solitary nodule or multi-nodular?
Papillary carcinoma Usually a solitary nodule
What are the lamellar calcified bodies present in papillary carcinomas?
Lamellar calcified bodies present are known as psammoma bodies
For papillary cancers, is there a good prognosis? (10year survival rate percentage)
Good prgnosis 95% survival at 10years
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The reasons they are called papillary cancerss due to the appearance of the cells
What is the second most common thyroid cancer? How is it differentiated from the benign adenoma version?
Follicular carcinoma Need vascular or capsular invasion to differentiate from folicular adenoma
What cells are medullary thyroid cancers derived from? What can it secrete? What gene is it associated with?
C cells Can secrete calcitonin Associated with the Ret gene
Medullary thyroid cancers are usually aggressive, how should they be treated?
Total thyroidectomy
What local effects can medullary thyroid cancer cause?
Dysphagia , hoarseness, and airway compromise
Medullary thyroid cancers can cause an increased prduction of VIP and ACTH, what can these cause?
Vasoactive intestinal peptide (VIP) can cause diarrhoea ACTH can cause cushing’s disease
Whattype of thyroid cancer tends to occur in older patients and is rapidly growing resulting in death in lot of patients?
Anaplastic thyroid carcinoma
Aspirates are interpreted without architecture – provide a minimally invasive assessment of the likelihood of malignancy - used for thyroid cytology (structure of cells) Thy 1 – insufficient/uninterpretable Thy 2 – benign Thy 3 – atypia probably benign/equivocal Thy 4 – atypia suspicious of malignancy Thy 5 – malignant What are follicular lesions graded as and why?
Due to the fact the relationship to the capsule is not assessed in an aspiration, the follicular lesions (adenomas or carcinomas) are graded as Thy 3
What conditions are parathyroid cancers associated with?
Can be associated with both MEN1 and MENIIa
What is the 22q11 deletion, that can result in hypoparathyroidism known as?
DiGeorge syndrome
Trousseau sign, Chovstek sign and QT prolongation (on ECG) What is this a deficiecny of and what is it caused by?
Hypocalcaemia Can be caused by hypoparathyroidism
