Thyroid Flashcards
Where is the TSH receptor located?
- surface of thyroid epithelial cells
What is used to control the production of T3 and T4?
- Inhibitory feedback loops
Explain thyroiditis?
- inflammation of the thyroid gland
Cause of thyroiditis?
- Autoimmune (Hashimotos, Graves)
- De Quervains
- Infection
What causes the symptoms of hyperthyroidism?
- Increased T3 and T4
Hyperthyroidism is also known as what?
- Thyrotoxicosis
What are some causes of hyperthyroidism?
- Graves
- Adenoma
- Thyroiditis
- Ectopic production
What are some symptoms of hyperthyroidism?
- anxiety
- palpitations
- weight loss
- loose stool
- heat intolerance
What investigations should be done for hyperthyroidism?
- TSH
- T3 and T4
What investigation can be performed to test for Grave’s disease?
- TSH receptor antibodies
TRAb
What is the first line treatment for hyperthyroidism?
- carbimazole
What treatments can be used for hyperthyroidism?
- carbimazole
- propylthiouracil
- radioactive iodine
- b blockers
Grave’s disease is what type of condition?
- autoimmune
What antibodies are associated with Grave’s disease?
- TSH receptor antibodies
What triad of features of hyperthyroidism can be seen?
- exophthalmos
- pretibial myxoedema
- acropathy
Symptoms of de quervain’s thyroiditis?
- fever
- neck pain
- dysphagia
What is the phases of de quervains thyroiditis?
- initial hyperthyroidism
- followed by hypothyroidism
What is a thyroid storm?
- rare presentation
- acute increased production of thyroid hormone
- admission
Hashimoto’s thyroiditis is what condition?
- autoimmune
- hypothyroidism
What are some causes of hypothyroidism?
- Hashimotos
- iodine deficiency
- drugs for hyperthyroidism
- post-surgery
Symptoms of hypothyroidism?
- weight gain
- fatigue
- hair loss
- oedema
Treatment for hypothyroidism
- levothyroxine
What age group does Hashimoto’s thyroiditis typically effect?
- 40-50
What autoimmune sign is seen in Hashimoto’s thyroiditis?
- anti-thyroid antibodies
Hashimoto’s thyroiditis increases the risk of other auto-immune conditions? True or false
- True
Goitre describes what?
- any enlargement of the thyroid gland
- hyper or hypothyroidism can cause
What often causes a goitre?
- lack of dietary iodine
Diffuse goitre?
- iodine deficiency
- usually normal thyroid function
Multi-nodular goitre?
- evolution from long standing simple goitre
- low risk of malignancy
What are the different carcinomas of the thyroid?
- papillary
- follicular
- medullary
- anaplastic
What is an example of a thyroid adenoma?
- follicular adenoma
What may cause a papillary carcinoma?
- ionising radiation
What may cause a follicular carcinoma?
- iodine deficiency
What is the most common form of thyroid cancer?
- papillary carcinoma
What does papillary carcinoma arise from?
- follicular cells
What spread would papillary carcinoma tend to spread via?
- lymphatic
What are symptoms of papillary thyroid carcinoma?
- lesion
- hoarseness
- dysphagia
What is the 2nd most common type of thyroid cancer?
- follicular carcinoma
What is the spread route of follicular carcinoma?
- haematogenous
What cell type does medullary thyroid carcinoma arise from?
- c-cells
Explain anaplastic carcinomas of the thyroid?
- undifferentiated
- aggressive
When does the thyroid gland begin to develop?
- 4th week of embryogenesis
Where does the thyroid gland originate?
- thickening of the back of tongue
- foramen caecum
Where does the thyroid gland descend down?
- thyroglossal duct
Remnant of the thyroglossal due can be called?
- pyramidal lobe
What spinal level does the thyroid gland sit?
- C5-T1
What is the arterial supply to the thyroid gland
- superior and inferior thyroid artery
Explain the steps in thyroid hormone synthesis
- thyroglobulin synthesis
- uptake and concentration of iodide
- oxidation of iodide to iodine
- iodination of thyroglobulin
- formation of MIT and DIT
- T3 and T4
What is the most abundant thyroid hormone?
- T4
What is the most potent thyroid hormone?
- T3
- 4 times more potent than T4
What transports the thyroid hormones?
- Thyroxine binding globulin
- TBG
What is the role of de-iodinases?
- derogates T3 and T4
- Mainly D3 and D1 involved
Where would the de-iodinases enzyme D3 be found?
- fetal tissue
- placenta
- brain (except pituitary)
What investigations should be performed for a solitary thyroid nodule?
- TSH
- USS fine needle aspiration
What is the treatment for a low risk differentiated thyroid cancer?
- lobectomy
What is the treatment for a high risk differentiated thyroid cancer?
- total thyroidectomy
- also consider radioactive iodine
What tumour cell marker can be used for follow up patients with previous thyroid cancers?
- thyroglobulin (Tg)
What is the frequency of TSH measurements for patients with previous thyroid cancer?
- TSH every 6 months for 5 years
- TSH every year for a further 5 years
What puts an increased risk of thyroid lymphoma?
- hashimoto’s thyroditis
What is the diagnostic tool for thyroid lymphoma?
- core biopsy
Treatment of thyroid lymphoma?
- steriods
- r-chop chemo
- radiotherapy
What cells are involved in medullary thyroid carcinoma?
- c-cell
What investigations are done for multinodular goitre?
- TSH
- CT scan
Treatment for a multinodular goitre?
- leave alone?
- radioactive iodine
- surgery
Describe primary thyroid disease
- disease affecting the thyroid gland itself
Describe secondary thyroid disease?
- hypothalamic or pituitary disease
- no thyroid pathology
What thyroid hormones are measured?
- TSH
- Free T3
- Free T4
What does TSH levels reflect?
- reflects tissue thyroid hormone action
Where is T4 deionised to T3?
- liver
Explain the blood results you would expect with primary hyperthyroidism?
Free T3/4 = high
TSH = low
Explain the blood results you would expect with secondary hyperthyroidism?
Free T3/4 = high
TSH = high or normal
Explain the blood results you would expect with primary hypothyroidism?
Free T3/4 = low
TSH = High
Explain the blood results you would expect with secondary hypothyroidism?
Free T3/4 = low
TSH = normal or low
Define myxoedema
- severe hypothyroidism
- medical emergency
Explain pretibial myxoedema?
- rare clinical sign of Grave’s disease
What are some primary causes of hypothyroidism
- Hashimotos
- iodine deficiency
- post-radiotherapy
What are some secondary causes of hypothyroidism?
- infection
- malignancy
- trauma
Clinical features of hypothyroidism?
- weight gain
- decreased appetite
- constipation
- depression
- reduced heart rate
Treatment of hypothyroidism?
young pt - levothyroxine 50-100ug daily
elderly pt - levothyroxine 25-50ug daily
Once commencing levothyroxine when should you check TSH levels?
- after 2 months
In secondary hypothyroidism what blood result is unreliable?
- TSH
- use free t4/3
Hashimoto’s thyroiditis is associated with what autoantibody?
- TPO antibodies
Symptoms of a myxoedema coma?
- bradycardia
- heart block
- type 2 resp failure
Treatment of myxoedema coma
- rewarm
- antibiotics
- thyroxine
Define thyrotoxicosis?
- cels exposed to excess thyroid hormones
Symptoms of thyrotoxicosis
- palpitations, AF
- Tremor
- sweating
- heat intolerance
- weight loss
Causes of thyrotoxicosis which are not associated with hyperthyroidism?
- de quervains
- postpartum thyroditis
- over treatment of levothyroxine
What autoantibody is associated with Grave’s disease
- TSH receptor antibody (TRAb)
Symptoms of Grave’s disease
- pretibial myxoedema
- thyroid acropachy
- thyroid bruit
- eye disease
Symptoms of thyroid storm?
- resp and cardiac collapse
- exaggerated reflexes
What antithyroid drug should be used in the 1st trimester of pregnancy?
- propylthiouracil
What is a side effect of anti-thyroid drugs?
- agranulocytosis
Explain agranulocytosis?
- low WCC
- side effect of anti-thyroid drugs
- warn patient if fever, oral ulcer or oropharyngeal infection STOP DRUG
What is the beta-blocker of choice in hyperthyroidism?
- propranolol
When might radio iodine be used?
- relapse of Grave’s disease
What is radioactive iodine contraindicated in?
- pregnancy
Risk during thyroidectomy?
- recurrent laryngeal nerve palsy
- hypothyrodism
- hypoparathyroidism
Explain subacute thyroiditis?
- may be triggered by viral infection
- self-limiting
What is the affect of amiodarone on the thyroid?
- abnormal TFTs
- high free T4
- low free t3
- normal TSH
Explain subclinical thyroid disease?
- abnormal TSH
- normal T4/3
Indication of a high risk subclinical hypothyroidism?
- TPO antibody postitive
Post operative checks after thyroidectomy?
- calcium levels
- whole body iodine scanning
