Clinical Thyroid Disease Flashcards by Zain Aslam

What are the 4 categories of thyroid disease?

Hyperthyroidism
Hypothyroidism
Goitre
Thyroid cancer

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What is the thyroid hormone pathway (from hypothalamus to thyroid?

TRH released onto anterior pit gland

TSH released from AP gland to thyroid

T3 = tri-iodothyronine
T4 - thyroxine both are released from thyroid

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Hypothyroid signs and symptoms ?

Everything slows down

Weight gain
Lethargy
Feeling cold
Constipation
Heavy periods
Dry skin/hair
Brady-cardia 
Slow reflexes

GOITRE

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Symptoms of hyperthyroidism?

Weight loss
Anxiety 
HEat intolerance
Bowel frequency 
Light periods
Palpitations 
Hyper-reflexia

GOITE

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What will hormone levels be if it is 1y hypo-T? Where does the problem lie?

Raised TSH
Low FT4 and FT3

Thyroid gland

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What will hormone levels be if it is 2y hypo-t

Low TSH
Low FT4 and FT3

Pit gland

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What is subclinical hypoT? What will hormone levels look like here?

When the pit gland goes into overdrive to maintain normal FT3 and FT4 levels

Raised TSH and Normal FT4 and FT3

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Prevalence of hypoT?

Commonest endocrine disease after diabetes

More common in women

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Causes of 1y hypoT?

Congenital
or
Acquired

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Describe the congenital causes of hypoT?

Can be developmental = agenesis/maldevelopment

Or due to dyshormonogenesis = trapping/organification/dehalogenase

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What is dyshormonogenesis?

A rare condition due to genetic defects in the synthesis of thyroid hormones

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Describe the acquired causes of hypoT?

Autoimmune - hashimotos
Iatrogenic
Chronic iodine deficiency
Post-subacute thyroiditis

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Name some iatrogenic causes of hypoT?

Postop/post-radioactive iodine
External radiotherapy for head and neck cancers
Antithyroid drugs

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Cause of 2y/3y hypothyroidism?

Pituitary or hypothalamic damage

Tumours
Post surgery etc

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Investigations for hypothyroidism?

Look for levels of TSH/FT4

Auto-antibodies :TPO - thyroid peroxidase antibodies

FBC - MCV will be increased
Lipids - hypercholesterolaemia

Hypernatremia

Increased muscle enzymes

Hyperprolactinaemia

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Treatment for hypothyroidism?

Levothyroxine (LT4) (T4 tablets) - 50mcg/day and increase after 2 weeks to 100mcg _ test regularly during this time to find perfect levels
After stabalisation organise annual check ups

There is also Liothyronine (T3)

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Is there a benefit to taking both levothyroxine and liothyronine together?

No - best to just take levothyroxine

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Half life of T4?

4 days

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What situations should special consideration be taken in regards to treatment?

Ischaemic heart disease
Pregnancy
Post-partum thyroiditis
Myxedema coma

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What special care should be taken if patient has ischaemic heart disease?

Start at a lower dose 25 mcg and increase cautiously - due to risk of precipitating angina

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What special care should be taken if patient is pregnant? Why?

Need an increase in LT4 dose by about 25% and keep TSH in a lower normal range and FT4 in a higher normal range

Should treat subclinical if planning on getting pregnant

Because hypothyroidism linked to foetal loss and lower IQ

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What special care should be taken if patient has post-partum thyroiditis?

You should trial a withdraw and measure TFTs in 6 weeks

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What special care should be taken if patient has myxedema coma

This is a very rare emergency and you may need IV T3 steroids

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What is myxedema coma?

Severe hypothyroidism leading to a decreased mental status, hypothermia and other symptoms connected to slowing of multiple organs

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When should treatment for subclinical hypothyroidism be considered?

Consider treatment if TSH is above 10 Above 5 with +ve thyroid antibodies Elevated TSH with symptoms

How should treatment be carried out in subclinical hypothyroidism?

Trial of therapy for 3/4 months and continue if symptomatic improvement

What is the risks of overtreatment in subclinical hypoT?

Afib Osteopenia - Bone density that is lower than normal peak density but not low enough to be osteoporosis

Causes of goitre?

Physiological - puberty, pregnancy Autoimmune - Graves, hashimotos Thyroiditis Iodine deficiency Dyshormogenesis

Goitre types

``` Multinodular Diffuse - colloid and simple Cysts Tumours - adenoma, carcinoma, lymphoma Misc. - Sarcoidosis, TB ```

What risk does a solitary thyroid nodule carry?

Risk of a malignancy - 5%

Solitary thyroid nodule investigations?

``` TFTs Ultrasound Isotope scanning Fine needle aspiration Chest and thoracic inlet X-rays if there is large retrosternal extensions ```

When would ultrasound scanning be useful?

Useful for separating into benign or malignant

When would isotope scanning be used?

If low TSH - hot nodule

What is a cold nodule?

A non-functioning thyroid nodule

What are the types of thyroid cancer?

Differentiated Anaplastic Lymphoma Medullary

What are the 2 differentiated cancers?

Papillary and follicular

Features of papillary?

Commonest Is multi-focal, local spread to lymph nodes Good prognosis

Features of follicular?

Usually a single lesion Mets to lung/bone Good prognosis of tumour is resectable

Management of differentiated thyroid cancer?

Prognosis is poorer compared to other thyroid disease Treatment is a near total thyroidectomy High dose radioiodine (ablative) Long term suppressive doses of thyroxine Follow ups with thyroglobulin and whole body iodine scanning following 2-4 weeks of thyroxine withdrawal

Is anaplastic cancer aggressive or not?

Aggressive and has poor prognosis - doesn't respond to radio-iodine External RT may be useful

Features of a lymphoma?

Rare May arise from pre-exisiting hashimotos thyroiditis Treatment - best is external RT combined with chemotherapy

Where does a medullary thyroid cancer arise from? What is it associated with? What hormone will be raised? Treatment and prognosis?

Parafollicular C cells` Associated with MEN 2 - phaeochromocytoma and hyperparathyroidism Serum calcitonin is raised Treatment - total thyroidectomy, there is NO role for radioiodine. Prognosis is variable

What are some 1y causes of thyrotoxicosis (hyperthyroidism)

Graves disease most common at 70% Toxic multinodular goitre Toxic adenoma

What are some 2y causes of thyrotoxicosis

Pituitary adenoma secreting TSH

When can their be thyrotoxicosis without hyperthyroidism?

Destructive thyroiditis | Excessive thyroxine administration (meds)

What can cause Destructive thyroiditis ?

Post-partum Amiodarone induced Subacute

Prevalance of graves?

2-3 per 1000 per year | More common in women

Graves features?

Autoimmune driven condition Thyroid peroxidase antibodies and TSH receptor antibodies involved

What part of the Hx should be taken into special consideration if a patient presents with suspected graves?

Family history of concurrent autoimmune disease

Graves disease diagnosis?

Test for TSH - will be low | T3 and T4 will be high

Symptoms specific to graves?

Clubbing like features Gynaecomastia Bulging eyes (Hyperthyroidism symptoms also)

Features of multi-nodular goitre?

Toxic nodules that secrete TH Seen in elderly and iodine def. patients Has a goitre but no graves disease and will not go into spontaneous remission

Features of subacute thyroiditis?

Also called de Quervain's Generally younger patients - less than 50 Viral trigger - enterovirus or coxsackie

Symptoms of subacute? Treatment?

Painful goitre with/without fever or myalgia. HAs an increased ESR May need short term steroid and NSAIDs

What is the overall management plan for hyperthyroidism

Beta blockers Anti thyroid drugs Radioactive iodine Surgery

What is the most commonly used anti thyroid med?

Carbimazole

How is carbimazole used?

2 ways - Titration or block regimens Titration - start on a high dose and gradually reduce to the lowest dose that works Block - block thyroid gland with a carbimazole then replace treatment with thyroxine before thyroid gland can recontinue Both have a 50% cure rate and a 30£ hypothyroidism rate, but block has higher side effects

When would ATDs be used over the others?

Elderly Cardiac complications Unwilling for RAI

2 ways RAI/radioiodine is used?

HIgh dose ablative - 90% cure but 70% hypothyroidism Variable calculated - 60-90% cure and less hypoTs

Risks of RAI?

High risk of hypothyroidism

Do patients usually choose ATD or RAI? What mode is usually given? When is it avoided?

ATD before RAI is tried Usually gived as a high dose albative Avouided in severe eye disease

What is subclinical HYPERthyroidism?

TSH is suppressed but there is normal FT3 and FT4