Thyroid Disorders Flashcards
What is the Isthmus of the Thyroid?
The bridge which connects the 2 lobes of the thyroid
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
Where is the thyroid cartilage in relation to the Thyroid gland?
Superior to the Thyroid
Where is the Thyroid gland located in the body?
In the neck anterior to the lower larynx and upper trachea
What is the embryological development of the Thyroid?
Originates in Foramen caecum and migrates down the Thyroglossal duct to where it then developed
What is Fascia?
Tissue that separates out different organs
What is the name of the Fascia that surrounds the thyroid?
Pretracheal fascia
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
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
Generally, what do Thyroid hormones do?
Control metabolic rate
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
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
How does Thyroid hormone regulate its own production? (Short explanation)
High T4 inhibits Hypothalamus (TRH) and pituitary (TSH)
What does Primary Hypothyroidism cause lack of?
Low free T4 (Thyroid hormone)
If free T4 levels are low, the level of what hormone is likely to be high to try and compensate?
TSH
What is Primary Hyperthyroidism?
Higher than normal levels of free T4
In Hyperthyroidism, If levels of free T4 are high, what are the levels of TSH likely to be like?
Low
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
Imaging methods to check the Thyroid are:
Ultrasound
Radioisotope scan
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
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
What is goitre?
Lump or swelling on the front of the neck due to a swollen thyroid
What is a retro sternal goitre?
Swollen thyroid gland in the chest behind the sternum can push windpipe to the side
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
