Thyroid Disorders Flashcards by Callum Donoher

What is the Isthmus of the Thyroid?

The bridge which connects the 2 lobes of the thyroid

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What is the name of the 2 blood vessels which supply the Thyroid gland with blood and which major blood vessel do they branch from?

Superior thyroid artery
Inferior thyroid artery

These 2 arteries branch from the common Carotid arteries

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Where is the thyroid cartilage in relation to the Thyroid gland?

Superior to the Thyroid

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Where is the Thyroid gland located in the body?

In the neck anterior to the lower larynx and upper trachea

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What is the embryological development of the Thyroid?

Originates in Foramen caecum and migrates down the Thyroglossal duct to where it then developed

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What is Fascia?

Tissue that separates out different organs

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What is the name of the Fascia that surrounds the thyroid?

Pretracheal fascia

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Why does the Thyroid move on swallowing?

The pretracheal fascia is connected to a special plane which moves up on swallowing and the Thyroid is found in here

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How can you tell if somebody a lump on someone’s neck is on the Thyroid?

Get them to swallow
If lump moves = on thyroid
If lump stays = not on thyroid

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Generally, what do Thyroid hormones do?

Control metabolic rate

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What systems of the body are affected by Thyroid disease and what are some symptoms?

Affect ALL systems:
Energy
Weight
Temperature
Heart rate
Nervous system
GI system
MSK
Skin

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How does Thyroid hormone regulate its own production? Longer explanation (Negative feedback)

When Thyroid levels are high it can INHIBIT:
-Anterior Pituitary reducing TSH synthesis
-Hypothalamus inhibiting TRH (Thyrotropin Releasing hormone) which means the Anterior Pituitary does receive stimulation to produce TSH so Thyroid is not simulated

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How does Thyroid hormone regulate its own production? (Short explanation)

High T4 inhibits Hypothalamus (TRH) and pituitary (TSH)

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What does Primary Hypothyroidism cause lack of?

Low free T4 (Thyroid hormone)

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If free T4 levels are low, the level of what hormone is likely to be high to try and compensate?

TSH

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What is Primary Hyperthyroidism?

Higher than normal levels of free T4

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In Hyperthyroidism, If levels of free T4 are high, what are the levels of TSH likely to be like?

Low

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How do you examine a patients Thyroid?

Feel the neck from behind
Should not feel if thyroid is enlarged
Swallow to feel if lump moving

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Imaging methods to check the Thyroid are:

Ultrasound
Radioisotope scan

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What radioisotope is usually used when imaging the Thyroid in a radioisotope scan and why?

Iodine
Iodine taken up into Thyroid gland
Thyroxine is made up of iodinated tyrosine

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What is a lingual Thyroid and why might it exist?

Thyroid tissue up by the tongue
Some of the thyroid remained at the Foreamen caecum and did not migrate fully down the Thyroglossal duct during embroylogical development

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What is goitre?

Lump or swelling on the front of the neck due to a swollen thyroid

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What is a retro sternal goitre?

Swollen thyroid gland in the chest behind the sternum can push windpipe to the side

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What is myxoedema?

Swelling of the skin due to build up of mucus and fluid

What are the symptoms of Hypothyroidism?

Tiredness Weight gain Cold intolerance Hange in appearance (myxoedema) Depression Constipation Puffy eyes

What are the signs of hypothyroidism?

Peri-orbital oedema (puffy swelling eyes) Bradycardia Cold peripheries Carpal tunnel syndrome (fluid builds up on median nerve)

What causes Hypothyroidism?

AUTOIMMUNE Hashimotos Thyroiditis Post-partum thyroiditis Dyshormonogensis (congenital defect of thyroid metabolism) Medication (Amioderone = slow release iodine) IODIINE DEFICIENCY (Can’t make Thyroxine)

What is Hashimotos Thyroiditis?

When autoimmune antibodies target the Thyroid gland causing the gland to become inflamed and swell producing GOITRE

Why are landlocked countries likely to have endemic goitres?

Lack of iodine in diets

How do we treat Hypothyroidism? Who should we be careful of treating?

Provide Lifelong thyroxine (T4) Be careful providing thyroxine to the elderly and people with heart disease since T4 increases heart rate

How can you tell if the dose of T4 being provided to treat Hypothyroidism is working?

Symptoms resolve If TSH is high, need to give more T4 If TSH low need to reduce amount of T4 given

What is a Myxoedema coma?

Severe Hypothyroidism Causes Hypothermia and fluid overload in heart pericardial effusion

How do we treat the emergency of Myxoedema coma?

Rapid IV fluids Hydrocortisone (Myxoedema coma usually happens alongside an Adrenal crisis) Gradual Rewarming

What is hydrocortisone?

A Glucocorticoid steroid drug

What is borderline/sub-clinical hypothyroidism?

When a patients fT4 levels are normal but on the lower range causing the Anterior pituitary to increase TSH levels

Would you normally treat sub clinical/borderline hypothyroidism straight away?

Not normally, monitor until symptoms warrant treatment since it usually corrects itself If woman is planning pregnancy, normally give Thyroxine since it is essential for healthy brain development

What is Malaise?

General feeling of weakness and illness

What are the symptoms of Hyperthyroidism?

Weight loss Irritability Insomnia Sweating Palpitations Tremor

What are the signs of hyperthyroidism?

Hyperkinesis Tachycardia Hypertension Atrial fibrillation Lid lag Proximal myopathy Warm peripheries

What is hyperkinesis?

Cans stop moving

What is Proximal myopathy?

Symmetrical weakness of Proximal muscle of lower and or upper limbs

Why do Goitres caused by Hyperthyroidism have a whooshing sound when listened to?

Thyroxine increases blood pressure and decreases peripheral vascular resistance This increases vascularity so more blood flows through here

In Graves’ disease, Why can the eye pop out and the lid retract with hyperthyroidism?

The Autoimmuneantibodies that that target the TSH receptors can also attack the fat and muscle in the back of the eye pushing it outwards

What is Proptosis?

The bulging of one or both eyes out of the normal position

Why does lid retraction occur in Hyperthyroidism?

Thyroxine increases sympathetic tone Sympathetic branch of the levator palpabrae superioris stimulated pulling back eyelid

What can cause Hyperthyroidism?

Graves’ disease Nodular thyroid disease Thyroiditis

What is type of disease is Graves’ disease?

Autoimmune

How does Graves’ disease cause Hyperthyroidism?

Autoimmune antibodies stimulate the receptors that TSH would normally act on This stimulates the over production of Thyroxine

What is Grave Opthalmopathy?

When the eyelids get retracted due to action of the autoantibodies in Graves’ disease

What is pretibial Myxoedema?

Is a Graves Dermopathy Where autoantibodies from Graves’ disease get deposited under the skin at the shins

What is Thyroid acropachy?

Looks like clubbing which is increased deposition around nail beds

What is Thyroiditis and what causes the Hyperthyroidism?

Inflammation of the Thyroid Destruction of thyroid cells releases Thyroxine into the blood Usually as a result of a virus

How can we treat hyperthyroidism?

Medication Surgery

What medication can be given to treat hyperthyroidism and what are the risks?

Carbimazole or Propylthiouracil (PTU) Carbimazole flattens immune system, causes agranulocytosis = low granulocytes in blood like neutrophils

What is Thyroid crisis?

Hyper Pyrexia Tachycardia Cardiac failure Liver dysfunction

Hyperthyroidism and pregnancy issues

Graves’ disease antibodies can be passed to fetus HCG is similar to TSH so HCG may stimulate the Thyroid to make Thyroxine in pregnant women

What are the red flags for thyroid cancer? (Rare)

Very young/old patient Rapid enlargement of lump in neck Dysphagia = trouble swallowing Hoarse voice (laryngeal nerve infiltrated) Family story of thyroid cancer

What might you notice on examination if a patient has Thyroid cancer?

Cervical lymph nodes swollen Hard irregular thyroid mass Lump fixed to surrounding structures

To treat a thyroid cancer surgery must be done, what must we be careful of while carrying out the surgery?

Avoid damage of the Laryngeal nerve to prevent Laryngeal nerve palsy (causes hoarse voice) Avoid accidentally removing the parathyroid glands causing hypocalcaemia