Causes of primary hypothyroidism - congenital causes (2) - acquired causes (4)

Congenital - maldevelopment - dyshormonogenesis Acquired - hashimoto's thyroiditis/disease (autoimmune thyroiditis) - iatrogenic - from radioactive iodine, radiotherapy - chronic iodine deficiency - post partum thyroiditis

Causes of central (i.e. pituitary or hypothalamus) hypothyroidism - neoplastic (2) - infiltrative (1) - traumatic (3) - iatrogenic (2)

neoplastic - pituitary tumour (prevents TSH production) - hypothalamus trauma or tumour infiltrative -infection, e.g. TB, syphilis traumatic - head trauma - pituitary apoplexy - sheehan's syndrome (pituitary necrosis due to blood loss and hypovolemic shock post birth) iatrogenic - pituitary surgery - pituitary radiotherapy

Thyroid gland clinical Flashcards by Heo Mun Ho

Symptoms/signs of hypothyroidism (11) - think metabolism is lowered

Weight Gain
Lethargy
Cold intolerance
Constipation
Mental slowness
Depression
Myalgia/ muscle weakness
Dry Skin/Hair
Bradycardia
Slow reflexes
GOITRE

Severe hypothyroidism
-puffy face, large tongue, hoarse voice

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Symptoms/signs of hyperthyroidism (14) - think metabolism is increased

Weight loss
Anxiety/irritability
Heat intolerance
Bowel frequency increase - diarrhoea
Frequent urination
Light periods
Sweating
Hair loss/thinning
Palpitations
Hyper-reflexia/tremors
GOITRE
Red/dry eyes
Osteoporosis

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State the common tests of thyroid function and their interpretation, and the methods available for thyroid imaging.

TSH
FT4
FT3

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Describe the levels of TSH, FT4 and FT3 in

primary hypothyroidism
subclinical (compensated) hypothyroidism)
secondary hypothyroidism

Raised TSH, Low FT4 & FT3

Raised TSH, Normal FT4 & FT3

Low (or normal) TSH, Low FT4 & FT3

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How is congenital hypothyroidism identified/screened for

screened for after birth in heel prick test

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Management of hypothyroidism in the newborn

Levothyroxine

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Causes of primary hypothyroidism

congenital causes (2)
acquired causes (4)

Congenital

maldevelopment
dyshormonogenesis

Acquired

hashimoto’s thyroiditis/disease (autoimmune thyroiditis)
iatrogenic - from radioactive iodine, radiotherapy
chronic iodine deficiency
post partum thyroiditis

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Hashimoto’s thyroiditis aka

Chronic immune/lymphocytic thyroiditis

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Most common cause of primary hypothyroidism

Hashimoto’s disease (Autoimmune thyroiditis)

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Causes of central (i.e. pituitary or hypothalamus) hypothyroidism

neoplastic (2)
infiltrative (1)
traumatic (3)
iatrogenic (2)

neoplastic

pituitary tumour (prevents TSH production)
hypothalamus trauma or tumour

infiltrative
-infection, e.g. TB, syphilis

traumatic

head trauma
pituitary apoplexy
sheehan’s syndrome (pituitary necrosis due to blood loss and hypovolemic shock post birth)

iatrogenic

pituitary surgery
pituitary radiotherapy

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Signs of a pituitary mass causing hypothyroidism

Papilloedema

Bitemporal hemianopia

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Biochemical investigations of primary hypothyroidism (e.g. Hashimoto’s thyroiditis) + typical findings of these (5)

hint: 2 autoantibodies

serum TSH - high

free serum T4 (FT4) - low

Autoantibodies

thyroid peroxidase (TPO) antibodies - elevated
anti-thyroglobulin antibodies - elevated

serum cholesterol - high

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Treatment of primary hypothyroidism

Lifelong once daily levothyroxine (T4)

-initially 50 micrograms/day then adjust dose in increments of 12.5 to 25 micrograms to normalise TSH

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Pathogenesis of Hashimoto’s disease (5)

Autoimmune destruction of thyroid involving thyroid peroxidase antibodies attacking the gland

lymphocytic infiltrate into the gland
destruction of thyroid follicles
apoptosis of thyroid epithelial cells
extensive fibrosis
Hurthle cell change

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Special situations where treatment of hypothyroidism (referring to dose of levothyroxine) differs to usual

IHD
-start at lower dose and increase cautiously as can precipitate angina

Pregnancy
-need increased dose as increased demand for thyroid hormone in foetus

Myxedema (aka SEVERE HYPOTHYRDOIDISM) coma
-may need IV T3

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What is myxoedema + what do you get it in

aka SEVERE HYPOTHYRDOIDISM

deposits of chains of sugar molecules (complex mucopolysaccharides) in the skin cause myxoedema
these compounds attract water, which lead to swelling

-swelling of face and esp lower legs

get it in hypo and hyperthyroidism (esp graves)

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Levothyroxine doesn’t usually have side effects but over-treatment can lead to what side effect

Hyperthyroidism symptoms - sweating, chest pain, weight loss, palpitations

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Why is there the need to increase dose of levothyroxine during pregnancy

as extra thyroid hormone needed for foetal nervous development

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Causes of a goitre (6)

Physiological

puberty
pregnancy

Autoimmune thyroiditis

grave’s disease
hashimoto’s disease

Non-autoimmune thyroiditis

Iodine deficiency

Dyshormogenesis

Goitrogens

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Types of goitres (5)

Multinodular goitre

Diffuse goitre (colloid or simple)

Cysts

Tumours (adenoma or carcinoma or lymphoma)

Miscellaneous causes (sarcoidosis, TB)

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A solitary thyroid nodule has risk of what

malignancy

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Investigations of a solitary thyroid nodule/ potential thyroid cancer (5)

TFTs - TSH, fT4

Ultrasound - differentiates benign v malignant

Fine needle aspiration (FNA) biopsy

Laryngoscopy - if vocal cords paralysed, suggests malignancy

Isotope thyroid scan - to look for hot/cold nodule

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Nodules detected on a thyroid scan can be hot or cold

-what’s the difference

Thyroid scan involves giving radioactive iodine to see if there’s any region that’s over-producing or under-producing thyroid hormone

Hot nodule - a nodular region of the thyroid gland that takes up large amounts of radioactive iodine relative to the rest of the thyroid gland so it’s producing too much hormone and shows up darker

Cold nodule - nodule is composed of cells that do not make thyroid hormone (don’t absorb iodine) (i.e. non functioning nodule) so appears as defect/hole in the scan

Do cold or hot solitary thyroid nodules have high risk of malignancy

Cold

Types of thyroid cancer (4)

(Well) Differentiated thyroid carcinoma (good prognosis) - papillary - follicular Anaplastic (poor prognosis; aggressive) Lymphoma (poor prognosis; rare) Medullary

Most common type of thyroid cancer

Papillary thyroid cancer

What underlies pathogenesis of most thyroid cancers

Genetic mutations

Papillary thyroid carcinomas often spread to where

local lymph nodes

Follicular thyroid carcinomas often spread to where

Lung/bone via blood rather than lymph

Thyroid cancer management - differentiated thyroid cancers (3) - anaplastic (1) - medullary (2) - lymphoma (2)

Differentiated - thyroidectomy - radioactive iodine ablation after surgery - long term levothyroxine - to suppress TSH Anaplastic -palliative surgery if possible but treatment based on chemoradiotherapy as it's aggressive and spreads so surgery not that helpful Medullary - thyroidectomy - then thyroid replacement (levothyroxine) - replacement rather than suppression as medullary cancer not TSH sensitive Lymphoma - chemotherapy - radiotherapy

Describe anaplastic thyroid cancer - characteristic - spread

Aggressive Locally invasive and can metastasise doesn't respond to radioactive iodine treatment

Thyroid lymphomas are rare and generally arise from pre-existing what

Hashimoto's thyroiditis

Medullary thyroid cancer is a tumour of what cells of the thyroid

parafollicular C cells

Medullary thyroid cancer is often associated with what genetic syndrome

Multiple endocrine neoplasia (MEN) type II

MEN type II (a genetic syndrome) predisposes you to what conditions (3)

Medullary thyroid cancer Phaeochromocytoma Hyperparathyrodism

Clinical features of thyroid cancer (5)

MAIN SIGN (may be the only sign people get)- palpable thyroid nodule - firm, immobile If advanced - hoarseness - dysphagia - dyspnoea - cervical lymphadenopathy

Describe the levels of TSH, FT4 and FT3 in - primary hyperthyroidism - subclinical (compensated) hyperthyroidism) - secondary hyperthyroidism

High FT4, FT3; Low TSH Normal FT4, FT3; Low TSH High FT4, FT3; High or normal TSH

Cause of secondary hyperthyroidism (rare)

Pituitary adenoma secreting TSH

Pathogenesis of grave's disease

Immune system produces TSH receptor antibodies which excessively stimulate thyroid gland to produce thyroid hormones, and consequently also causing hypertrophy of gland

Biochemical investigations of grave's disease (4)

serum TSH - low serum T4/T3 - high detectable TSH receptor antibodies - specific to grave's high thyroid uptake of radioactive iodine test

Untreated hyperthyroidism, particularly in older people, may result in what complications

cardiac arrhythmias, high-output cardiac failure, bone mineral loss

Symptoms (3) /signs (7) of grave's disease

Symptoms - heat sensitivity - sweating - palpitations/ fast irregular heartbeat --> AF Signs - Graves' ophthalmopathy - upper eyelid retraction, EXOPHTHALMOS, red etc - PRETIBIAL MYXOEDEMA (thyroid dermopathy) - acropachy - soft-tissue swelling of the hands and clubbing of the fingers - fine tremor - weight loss - DIFFUSE goitre

Causes of thyrotoxicosis without hyperthyroidism (3)

Post partum thyroditis Subacute (de Quervain's) thyroiditis Excessive therapeutic thyroxine

What is subacute (de Quervain's) thyroiditis

Painful swelling of the thyroid gland thought to be triggered by a viral infection, such as mumps or the flu fever and pain in the neck causes initial hyperthyroidism followed by transit hypothyroidism

Palpitations and shakes/temors associated with thyrotoxicosis can be treated with

beta blockers

Treatment of grave's disease (hyperthyroidism) (4)

Antithyroid drugs - carbimazole - propylthiouracil Radioactive iodine therapy +/- steroids Thyroidectomy ``` beta blockers (propanolol) -reduce symptoms of tremor, tachycardia and palpitations; doesn't cure the condition ```

Antithyroid drugs given for hyperthyroidism can be given in what different regimens + which is favoured

Titration regimen - start high dose then reduce gradually when thyroid levels improve Block-replace - blocking thyroid with constant dose then replacing with thyroxine when thyroid levels improve Titration regimen because less side effects

Who should radioactive iodine not be given to

Pregnant/breast feeding women

Possible complications of treatment of hyperthyroidism | -side effects of radioactive iodine, antithyroid drugs (propylthiouracil, carbimazole)

High dose radioactive iodine -risk of hypothyroidism Antithyroid drugs - propylthiouracil can be liver toxic - carbimazole and propylthiouracil may cause agranulocytosis

What is cretinism

severe hypothyroidism in the newborn - classically the result of maternal iodine deficiency --> physical and mental impairment

In early stages of Hashimoto's disease, damage to the thyroid follicles actually may cause a transient phase of what

hyperthyroidism due to release of thyroglobulin after damage of thyroid follicles

Histological features of Hashimoto's disease (4)

Dense lymphocyte and plasma cell infiltration --> lymphoid follicles Colloid content reduced Hurthle cell change - thyroid epithelium enlarge and develop eosinophilic granular cytoplasm Fibrosis

Histological features of Grave's disease (3)

Hyperplasia of acinar epithelium Reduced colloid content Accumulation of lymphocytes with lymphoid follicle formation

Why does grave's disease cause opthlamopathy

Because ocular fibroblast cells also have TSH receptor which the TSH receptor antibodies can attack

Are most follicular adenomas (thyroid tumour) functioning or non-functioning

Non-functioning

Follicular adenoma v follicular carcinoma

Follicular adenoma - encapsulated tumour Follicular carcinoma - malignant cells breach capsule and spread outmatch thyroid

What thyroid cancer is characterised by psammoma bodies

papillary carcinoma