Thyroid Disorders Flashcards
How does hypothyroidism present? [8]
Severe cases [4]
- Weight Gain
- Cold intolerance
- Brittle nails, thin/dry skin & hair
- Hyporeflexia, slow speech
- Lethargy & low mood
- Constipation
- Bradycardia
- Heavy periods
Severe cases can cause puffy face, large tongue, hoarseness and coma
How does hyperthyroidism present? [9]
- Weight loss
- Heat intolerance
- Hyperreflexia
- Bowel frequency
- Palpitations
- Light periods
- Sweaty palms
- Thyroid eye symptoms (bulging)
- Anxiety/irritibility
How does gender affect thyroid disease?
Both hyper and hypothyroidism are much more common in women
What are the types of Hypothyroidism? [3]
Primary
Subclinical
Secondary
What causes congenital Hypothyroidism? [2]
- developmental problems e.g. agenesis
- Dyshormogenensis (autosomal recessive condition preventing TH production)
What causes acquired Primary Hypothyroidism? [4]
- Autoimmune (hashimoto’s) thyroiditis
- Iatrogenic
- Chronic Iodine Deficiency
- Post-subacute thyroiditis
What can cause secondary or tertiary hypothyroidism? [4]
- Pituitary tumours
- Craniopharyngioma
- Pituitary surgery/radiotherapy
- Sheehan’s Syndrome
- Isolated TRH deficiency
What is Sheehan’s Syndrome? [2]
Post-partum ischaemic necrosis [1] of the pituitary due to blood loss/hypovolaemic shock of childbirth [1]
List some iatrogenic causes of primary hypothyroidism? [4]
Post op
Radioactive Iodine or Anti-Thyroids
Amiodarone (Sub-acute thyroiditis)
RT for H/N cancer
What tests would you run for suspected hypothyroidism? What are the expected results? [7]
- TFTs i.e. TSH & fT4
- Thyroid Peroxidase Antibodies
- FBC (MCV inc)
- Lipids (inc)
- Hyponatremia
- Elevated Muscle enzymes, ALT & CK
- Prolactin (inc)
Explain the results of the test for:
Lipids [1]
Hyponatremia [1]
Hyperprolactinemia [1]
Hypercholesterolaemia - decreased LDL receptors in liver
Na+ - Hyponatremia due to excess ADH from hypothyroidism
Hyperprolactinaemia - Increase TRH levels also stimulates an increase in prolactin levels
How will TFT’s (TSH, FT4) appear for each class of Hypothyroidism for:
Primary
Secondary
Subclinical
Primary - Low fT4 but high TSH
Secondary - Low fT4 & low or normal TSH
Subclinical - Normal fT4 & High TSH
What do we use to manage hypothyroidism? [4]
Levothyroxine (T4) tablets
Initial dose 50-100 mcg/day
Adjusted in steps of 25-50 mcg every 3-4w
Maintenance dose 100-200 mcg OD
Keep increasing until their TSH (primary disease) or fT4 (Secondary Disease) is normal.
What special cases affect how you use Levothyroxine? [4]
- IHD needs to be started lower and titrated slowly as it can trigger Angina
- Pregnant women need more T4
- Myxedema Coma needs IV T3
- Post-partum Thyroiditis needs to have the meds removed for 6 weeks and TFTs measured to see when it abates
What level is subclinical hypothyroidism [4]
Only if:
- TSH >10
- > 5 + Antibodies
- TSH elevated + symptoms (temporary trial therapy for symptom improvement)
- Pregnant or planning pregnancy
What are the risks of levothyroxine? [3]
Interactions [1]
- Thyrotoxicosis
- AF
- Osteopenia
Interactions: iron reduces absorption so give 2h apart
How does Goitre occur in hypothyroidism? [4]
No fT4
No -ve feedback
Excess TSH
Hyperstimulation -> Hyperplasia of Thyroid gland
What are the causes for Primary hyperthyroidism? [4]
Graves Disease - 70%
Toxic Multinodular Goitre - 20%
Thyroid Adenoma
Thyrotoxic phase of thyroiditis (eventual hypothyroidism)
What is Grave’s Disease? [2]
Autoimmune condition, TSH receptor antibodies [1] continuously stimulate the thyroid [1] causing Primary hyperthyroidism
What is Toxic Multinodular goitre?
Most common cause [1] and its pathogenesis [2]
Presentation [4]
Multinodular Goitre producing excess thyroid hormones Dietary iodine deficiency Rise in TSH to compensate Hypertrophy and hyperplasia of thyroid follicular cells Presentation: Cosmetic problem Airway obstruction Dysphagia SVC syndrome
Whats the main cause of secondary hyperthyroidism? [1]
Pituitary Adenoma producing TSH
What is Thyrotoxicosis without hyperthyroidism?
Name 2 causes
Where you get excess thyroid hormone without hyperthyroidism [1]
Due to exogenous thyroxine [1] or destructive thyroiditis causing stores of thyroid hormones to be released [1]
What causes destructive thyroiditis? [2]
Post-partum
Amiodarone induced
How do you diagnose Hyperthyroidism? [3]
Clinical features - associated conditions of Graves’ disease [2]
Clinical dx, TFT test, TSH receptor antibody test
Associated conditions:
- Thyroid eye disease
- Pre-tibial myxoedema
How will TFT’s (TSH, FT4) appear for each class of Hyperthyroidism for:
Primary
Secondary
Subclinical
Primary - High fT4 & low TSH
Secondary - High fT4 & High TSH
Subclinical - Normal fT4 & low TSH
How is Hyperthyroidism treated? [3]
1st) Anti-thyroid Drugs (ATDs)
2nd) Radioiodine
Resection of thyroid or pituitary adenoma
What are anti-thyroid drugs used? [2]
Carbimazole
Propylthiouracil
When would we treat Subclinical hyperthyroidism? [3]
If:
- Elderly
- Persistant subclinical hyperthyroidism
- High cardiac risk patient
Risks of Hyperthyroidism treatments? [2]
Carbimazole causes agranulocytosis
Radioiodine makes ~70% of patients hypothyroid and can cause eye disease
How would you investigate a thyroid lump? [5]
- TFTs
- Technetium 99 Isotope scan
- US (solid or cystic)
- FNAC
- CXR (retrosternal extension, mets)
IF you suspect cancer a serum calcitonin to rule out MEdullary Thyroid Cancer
What are the main types of thyroid cancer? [6]
Differentiated thyroid carcinoma: papillary, follicular ca
Anaplastic, Lymphoma and medullary thyroid cancer.
What is medullary thyroid cancer? [2]
What gene mutation is associated? [1]
Treatment [2]
Cancer of C cells in the thyroid gland [1]
Produces calcitonin [1]
Associated with MEN 2 gene mutation
Tx: total thyroidectomy, nodal clearance, no role for radio iodine
Treatments for Thyroid cancers?
High Dose radioiodine
Long-Term levothyroxine to suppress the tumour
Lymphoma - External RT/chemo
Anaplastic - Can be delayed with external RT
Thyroidectomy - Only treatment that works on medullary thyroid cancer
When would we stop Levothyroxine for Thyroid cancer?
Withdraw from the thyroxine for 2 weeks as a trial and do a full body radioisotope scan to see if its all gone
Thyroid storm represents a severe form of thyrotoxicosis. What exaggeration of hyperthyroidism symptoms can be seen? [2]
Heat intolerance > fever
Rapid HR > arrhythmia
Subacute thyroiditis (de Quervain's) hypothyroidism Trigger [2] Symptoms [4] Ix and result [1] Prognosis [1] Rx [2]
Viral trigger: enterovirus, coxsackie
Symptoms: painful goitre, fever, myalgia
ESR increased
Self limiting, 6-8w
Short term steroids 40mg OD weaned over 4 week period, NSAIDs, symptomatic control with B-blockers
Toxic adenoma Define [1] Presentation [2] Pathogenesis: explain what is meant by thyroid autonomy [2] Diagnosis [1]
Benign tumor that produces excess thyroid hormones
Painless solitary nodule + thyrotoxicosis sx
Patho: somatic mutation > follicular cells secrete thyroid hormone independent of stimulation (thyroid autonomy)
Diagnosis: biopsy
Differentiated thyroid carcinomas
Follicular ca - what common mutations are found in patients? [2]
Describe prognosis of follicular [1]
Ix [3]
Papillary - associated with good prognosis
Follicular ca - BRAF mutation, RET/PTC gene re-arrangement
Prognosis:
- Good prognosis if resectable
Ix: TFT, US, FNA
Differentiated thyroid carcinoma
Poor prognostic factors [4]
Age <16, >45
Tumour size
Spread outside thyroid capsule
Metastases
Management of Differentiated thyroid carcinoma
Near total thyroidectomy
High dose radio iodine
Long term thyroxine
Other types of thyroid cancer
Anaplastic - describe progression of disease, response to treatment, recommended tx
Anaplastic - aggressive, locally invasive, not responsive to radio iodine, try external RT
Struma ovarii
Define [1]
Treatment [2]
Ovary has differentiated in thyroid cells
Tx: thyroidectomy > RAI
Thyroid eye disease
Ax
RF
Px [2]
Ax: any form of thyroid disease (can be hypo, hyper or euthyroid)
RF: smoking
Px: autoimmunity leads to inflammatory response and periorbital oedema
Thyroid eye disease
Symptoms [3]
Signs [5]
Sy:
- eye discomfort, grittiness
- increased tear production
- diplopia, reduced acuity
Signs:
- exophthalmos (appearance of protruding eyes)
- proptosis (eyes protrude beyond orbit (look above in same plane as forehead))
- conjunctival oedema, corneal ulceration, papilledema
- loss of colour vision
- afferent pupillary defect (optic nerve compression = URGENT expert advice rqd)
Thyroid eye disease mx
- Mild [3]
- Severe [4]
- Mild:
- artificial tears, sunglasses, avoid dust
- elevate head when sleeping to reduce periorbital oedema
- Fresnel prism on one lense of glasses for diplopia
- Severe:
- IV METHYLPREDNISLONE
- if gross oedema or opthalmoplegia, surgical decompression with inferior approach using spaces of paranasal sinuses for severe sight threatening disease or cosmetic reasons
- eyelid surgery for cosmetic and function
- orbital RT (improves opthalmoplegia but little effect on proptosis)
Amiodarone effects on thyroid gland
A large proportion of amiodarone is comprised of iodine (37% by weight)
Amiodarone induced thyrotoxicosis
* Type 1 AIT
* Type 2 AIT
Amiodarone induced hypothyroidism
How does amiodarone cause thyrotoxicosis and hypothyroidism?
- structurally similar to thyroxine or T4 AND high iodine content > excess thyroid hormone synthesis
- amiodarone inhibits deiodination, reducing peripheral conversion of T4 to T3 so T4 levels rise by 20-40% in first month
- hypothyroidism - The Wolff Chaikoff effect describes the phenomenon whereby a large iodine load prevents iodine organification necessary for thyroid hormone synthesis. Hence, amiodarone, with its large iodine content, inhibits thyroid hormone synthesis and can result in hypothyroidism.
Differentiate the presentation of Type 1 amiodarone induced thyrotoxicosis and Type 2
Type 1 AIT
* pre-existing thyroid dysfunction
* goitre
* radioiodine uptake scan normal
* same treatment as Graves disease thyrotoxicosis
Type 2 AIT
* Destructive thyroiditis, damage to follicular cells results in release of thyroid hormone
* radioiodine uptake scan reduced
* treated with steroids to reduce conversion of T4 to T3.
What is Riedel’s thyroiditis
Riedel’s thyroiditis is rare and caused by a chronic fibrosing process, leading to a characteristic ‘woody’ sen- sation on palpation of the thyroid gland. It is associated with fibrosis of other structures including salivary glands and bile ducts (sclerosing cholangitis) and retroperitoneal fibrosis. Patients are euthyroid. Surgery may be required for symptomatic management.
