3.6 Hyperthyroidism Flashcards
When are the two important functions of TSH?
activates iodide uptake
activates the release of T3 and T4 into the blood stream
What does thyroxine do? (1)
Increase basal metabolic rate
What is TRH?
Thyrotropin releasing hormone
Where does TRH come from?
hypothalamus
What is the action of TRH?
TRH acts on thyrotrophs in the anterior pituitary, to secrete TSH
What does T3 and T4 feedback to?
T3 and T4 feedback negatively to the anterior pituitary and the hypothalamus
What will the TSH levels of a patient with primary hypothyroidism?
high
How do we adjust the dose of levothyroxine
Increase dose until TSH falls to normal
What is Graves’ disease?
Autoimmune disease where antibodies bind to and stimulate TSH receptors in the thyroid, resulting in hyperthyroidism
What are some of the observable features of graves’ disease?
breast enlargement
facial flashing
goitre (swelling of neck –> due to swelling of thyroid gland)
shortness of breath
weight loss
muscle wasting –> causing muscle weakness
perspiration
What are some of the non - observable features of graves’ disease?
feeling hot
increased appetite
tachycardia
diarrhoea
insomnia
nervousness/excitability/emotional instability
oligomenorrhea or amenorrhea
What symptoms in graves disease are caused by other antibodies not affecting the thyroid?
other antibodies bind to muscles behind the eye (cause growth) and cause exophthalmos
other antibodies cause pretibial myxoedema
What is pretibial myxoedema?
The swelling that occurs (non-pitting) on the shins of patients with graves disease.
myxoedema–> swelling of LL
caused by hypertrophy
What is the difference between myxoedema and pretibial myxoedema?
myxoedema caused by hyperthyroidism
pretibial myxoedema caused by Grave’s disease
What would you see if do a radio-iodine uptake scan a patient with graves disease?
uniform radioiodine uptake and enlarged thyroid gland
very dark as very active
What is toxic nodular goitre?
benign adenoma that is overactive at making thyroxine
What is the difference between toxic nodular goitre and graves disease?
toxic nodular goitre: NOT autoimmune NO pretibial myxoedema NO exophthalmos swelling on neck tends to be on one side
What would you see if do a radio-iodine uptake scan a patient with toxic nodular goitre?
lots of spill over, dark spot = ‘hot spot’ not uniform thyroid gland shape (as can be due to just hyperproliferation once cell thats secreting too much thyroxine, and rest of thyroid atrophys)
Why can hyperthyroidism be a medical emergency?
If hyperthyroidism gets extremely severe (high), the can have a thyroid storm.
Thyroid storm –> 50% mortality rate
What is the effect of thyroxine on the sympathetic nervous system?
sensitises beta adrenoreceptors to ambient levels of adrenaline and noradrenaline.
–> some symptoms similar to extra adrenaline (palpitations, tachycardia, tremor in hands, lid lag)
propanaol - beta blocker
What is thyroid storm?
Hyperthyroidism
AND TWO OR MORE OF:
- hyperpyrexia >41 degrees
- accelerated tachycardia/arrythmia
- cardiac failure
- delirium/frank psychosis (brain affected)
- hepatocellular dysfunction; jaundice (liver affected)
What are the treatment options for hyperthyroidism?
surgery
radioiodine
drugs
What are the four classes of drugs used in the treatment of hyperthyroidism?
- Thionamides
- Potassium Iodide
- Radioiodine
- Beta-blockers
