Biochemistry Flashcards
Is T3 or T4 a better marker of thyroid function?
T4
What % of T4 is free (fT4)?
Roughly 1% of the total T4, with the rest being bound to thyroid binding globulin
What is the half life of T4?
1 week
List 10 clinical features of hypothyroidism?
- Lethargy
- Increased weight
- Cold intolerance
- Memory impairment
- Menorrhagia
- Bradycardia
- Depression
- Dry skin
- Hair loss
- Constipation
List 6 clinical features of Grave’s disease?
- Exophthalmos/Proptosis
- Pretibial myxoedema
- Other autoimmune conditions
- Thyroid bruits
- Diffuse symmetrical goitre
- Chemosis
List 14 clinical features of hyperthyroidism?
- Tachycardia
- Palpitations (AF)
- Hyperactivity
- Decreased weight and appetite
- Muscle weakness & wasting
- Palmar erythema
- Goitre
- Hyperreflexia
- Fine tremor
- Onycholysis
- Diarrhoea
- Sweating
- Oligomenorrhea/Amenorrhoea
- Heat intolerance
Describe the biochemistry results of primary hypothyroidism?
- Raised TSH (due to no -ve feedback)
- Low T4 (due to thyroid’s inability to produce enough)
- Normal T4 & raised TSH suggests subclinical hypothyroidism (most commonly caused by underlying autoimmune disease)
List 7 causes of primary hypothyroidism?
- Autoimmune thyroiditis (50%)
- Iodine deficiency or excess
- Thyroidectomy
- Therapy with radioactive iodine
- External radiotherapy
- Drugs
- Thyroid agenesis/dysgenesis
Describe the biochemistry result of secondary hypothyroidism?
- Normal/low TSH (due to a lack of production)
- Low T4 (due to no +ve feedback from TSH)
List 4 causes of secondary hypothyroidism?
- Pituitary Adenoma- most common
- Surgery or radiotherapy which damages the pituitary tissue
- Hypothalamic/suprasellar tumour
- History of hypothalamic surgery or radiation
Describe the biochemistry results of primary hyperthyroidism?
- Raised T3/T4 (due to excessive production)
- Low TSH (due to -ve feedback on pituitary/hypothalamus)
List 5 causes of primary hyperthyroidism?
- Graves’ disease (75% of all cases)
- Toxic multinodular goitre
- Toxic adenoma
- Iodine-induced (rare)
- Trophoblastic tumour (very rare)
Describe the biochemistry results of secondary hyperthyroidism?
- Raised T3/T4 (due to excess production driven by a raised TSH level)
- Raised TSH (due to excess production)
List 3 causes of secondary hyperthyroidism?
- TSH-secreting tumour
- Chorionic-gonadotropin secreting tumours (hCG secreting)
- Thyroid hormone resistance (usually euthyroid)- TSH is resistant to T3/T4 -ve feedback
What 4 blood tests assess the liver’s synthetic function?
- Bilirubin
- Albumin
- Prothrombin Time (PT)
- Serum glucose
What are 4 causes of an isolated rise in ALP?
- Bony metastases / primary bone tumours (e.g. sarcoma)
- Vitamin D deficiency
- Recent bone fractures
- Renal osteodystrophy
What are 2 causes of isolated jaundice/rise in bilirubin?
- Gilbert’s syndrome (most common cause)
2. Haemolysis
What 5 blood tests would you do to confirm haemolysis?
- Blood film
- Full blood count
- Reticulocyte count
- Haptoglobin
- LDH levels to confirm
What is the cause of jaundice if you have normal stools & urine?
Pre-hepatic jaundice
What is the cause of jaundice if you have dark urine & normal stools?
Hepatic jaundice
What is the cause of jaundice if you have dark urine & pale stools?
Post-hepatic jaundice (obstructive)
List 3 causes of unconjugated hyperbilirubinaemia?
- Haemolysis (haemolytic anaemia)
- Impaired hepatic uptake (drugs, congestive cardiac failure)
- Impaired conjugation (Gilbert’s syndrome)
List 2 causes of conjugated hyperbilirubinaemia?
- Hepatocellular injury
2. Cholestasis
List 3 causes of a decreased albumin?
- Liver disease (e.g. cirrhosis)
- Inflammation –> acute phase response which temporarily decreases the liver’s production of albumin
- Excessive loss due to protein-losing enteropathies/nephrotic syndrome
