Hypo/hyperthyroidism Flashcards
What is the difference between primary and secondary thyroid disease?
Primary - disease is of the thyroid gland
Secondary - disease is of the hypothalamus/pituitary
What tests can measure thyroid function?
TSH
Free T4/T3
T4/T3 bound to proteins
What three proteins can T3/T4 be bound to?
TBG, albumin & pre-albumin
Is the thyroid axis positive or negative feedback?
Negative
What are the lab results in hypothyroidism?
primary - low T3/T4, high TSH
secondary - low T3/T4, low TSH
What are the lab results in hyperthyroidism?
primary - high T3/T4, low TSH
secondary - high T3/T4, high TSH
Describe subclinical hypothyroidism
TSH high, T3/T4 normal
State the two main types of hypothyroidism
Goitrous & Non-goitrous
Name four causes of goitrous hypothyroidism
- Hashimoto’s
- Iodine deficiency
- Drug induced
- Maternal transmission
State two causes of non-goitrous hypothyroidism
- Atrophic thyroiditis
- Iatrogenic
What is the most common cause of hypothyroidism in the western world?
Hashimoto’s thyroiditis
Describe Hashimoto’s
TPO antibodies (thyroid peroxidase) cause T cell infiltrate & inflammation of the thyroid gland
What are the clinical features of hypothyroidism?
- cold skin, puffy eyes, hypercarotenaemia
- cold intolerance
- pitting oedema
- bradycardia
- decreased appetite, increased weight
- constipation
- sleep apnoea
- low mood
- oligo/ammenorrhoea
- hyperprolactinaemia
In hypothyroidism what will happen to sodium?
It will decrease
What is the treatment for hypothyroidism?
Levothyroxine (T4)
What is the medical emergency associated with hypothyroidism?
Myxoedema Coma
Describe the typical presentation of myxoedema coma
Older women with undiagnosed/untreated hypothyroidism - severe medical emergency (60% mortality)
What does myxoedema coma lead to?
Accumulation of mucopolysaccharides in the dermis & other tissues which attract water and cause swelling
How can myxoedema coma be managed?
ABCDE
- identify & treat concurrent illness
- passively rewarm
- cardiac monitoring for arrhythmias
- antibiotics
- thyroxine & hydrocortisone
Define thyrotoxicosis
clinical, physiological & biochemical state arising when tissues are exposed to excess thyroid
Define hyperthyroidism
conditions which overactivity of thyroid gland leads to thyrotoxicosis
What are the clinical features of thyrotoxicosis?
- palpitations, AF
- tremor, sweating
- anxiety, nervousness, irritability
- frequent, loose bowel movements
- increased appetite, weight loss
- proptosis. lid retraction
- brittle, thin hair and skin
- intolerance to heat
- lighter, less frequent periods
- muscle weakness
State three things that can cause excess thyroid stimulation
- Graves Disease
- Hashitoxicosis
- Cancer
- Thyroid Nodules
State three causes of thyrotoxicosis not associated with thyroid disease
- Thyroid inflammation
- Exogenous thyroid hormones
- Ectopic thyroid tissue
What is the most common cause of hyperthyroidism in young people?
Grave’s Disease
Describe Grave’s Disease
TSH receptor antibodies (TRAb) act by stimulating thyroid hormone production
How does Grave’s Disease arise?
susceptible genes + environmental factors
What lifestyle factor significantly increases risk of Grave’s disease & treatment failure?
Smoking
What investigations should be carried out on a patient with suspected Grave’s disease?
TSH, T3/T4
Calcium, WCC, TRAb
Name four specific signs of Grave’s disease
- pretibial myxoedema
- thyroid acropachy
- thyroid bruit
- eye disease
What is the more common cause of hyperthyroidism in older patients?
Nodular disease - insidious onset asymmetrical goitre
Name the medical emergency associated with hyperthyroidism
Thyroid storm/crisis
How does thyroid storm present?
Severe systemic disease - respiratory/cardiac collapse & hyperthermia
How do you treat thyroid crisis?
Lugol’s iodine/potassium iodide
Glucocorticosteroids
Beta blockers
Fluids
What is first line treatment for hyperthyroidism?
Carbimazole
What is second line treatment for hyperthyroidism?
Propylthiouracil (inhibits DID1 to decrease conversion of T4 to T3 in the liver, less potent & may cause liver failure)
What is the potentially fatal side effect associated with drugs for hyperthyroidism?
Agranulocytosis - highest risk in first 6 weeks, in the event of the patient developing a fever the drug must be stopped immediately. Patient must be warned verbally & in writing
Name the beta blocker used in hyperthyroidism
Propanolol - useful for symptomatic relief
When is radio iodine used?
Relapsed Grave’s, nodular thyroid disease
What is the key risk of radio-iodine?
Hypothyroidism
State the treatment used when radio-iodine is contraindiciated
Thyroidectomy - surgical & anaesthetic risks
What is thyroiditis?
Inflammation of thyroid
State the causes of thyroiditis
- virus/bacteria
- hashimoto’s
- post partum
- drugs/radiation
Describe the disease progression of subacute thyroiditis
Triggered by viral infection, associated with neck tenderness, fever or viral symptoms. Usually self-limiting
What is a normal thyroid level called?
euthyroid
How does amiodarone relate to thyroid?
Drug has a high concentration of iodine.
Hypothyroidism can occur in iodine rich areas
Hyperthyroidism tends to occur in iodine deficient areas
How does hypothyroidism arise due to amiodarone?
High iodine content may inhibit thyroglobulin iodination and thyroid synthesis & release causing hypothyroidism
How does hyperthyroidism arise due to amiodarone?
Iodine excess can increase hormone synthesis or alternatively (type 2) due to toxicity of amiodarone thyroiditis occurs
What happens to thyroid physiologically during illness?
TSH is suppressed initially but rises during recovery
