Hyperthyroidism Flashcards
how is T4 made
1) Tsh binds to TSH receptors on follicular cells
2) production of TG and thyroperoxidase ( TPO)
3) iodine enters collide via Na+/I- transporters
4) TPO and hydrogen peroxide catalyse oxidation of Iodide –> iodine and TG + Iodine
5) Iodination of TG creates MIT or DIT ( mono and di iodothyronine)
6) Coupling reactions of MIT and DIT helped by TG + TPO/H2O2 form:
7) T3 ( 2 MIT) , T4 ( 2 DIT)
8) theses are cleaved from TG and transported in blood
Remember T4 is active thyroid hormone
What does thyroxine do
increase basal metabolic rate
What do you see in T4 /3 levels and TSH levels in primary hyperthyroidism
High T3/4 with low TSH ( remember T3 / T4 surprised TRH and pituitary due to -ve feedback)
For normal hydroid disease ( primary hyperthyroidism) what should be done to treat it
give levothyroxine dose until TSH becomes normal
Symptoms of hyperthyroidism
Weight loss despite increased appetite Breathlessness Palpitations , tachycardia Sweating ( feeling hot) Heat intolerance Diarrhoea Lig lag and other sympathetic features
What are the symptom of Grave’s disease
Heat intolerance
Raised metabolism → Increase in body temperature
Sweating
Weight loss
Higher basal metabolic rate
Despite increased appetite
Palpitations
Including atrial fibrillation or supraventricular tachycardias
breathlessness
Tremor
Exophthalmos (Proptosis)
Growth factor receptor immunoglobulins bind to muscles behind the eye
Smooth goitre
Oligomenorrhoea
Warm velvety skin
Occasional diarrhoea
Breast enlargement - gynecomastia in males
Muscle wasting
Breathlessness
Localised myxoedema
Pretibial myxoedema is the growth of soft tissue on the shin and associated (non-pitting swelling)
Lid lag and other SNS features.
Iodothyronines (thyroxine) sensitises GS linked beta-2-adrenoceptors (in sinoatrial node) to ambient levels of adrenaline and noradrenaline (NOT more adrenaline, just more sensitive receptors).
Leads to apparent SNS activation → tachycardia, lid lag, hand tremor etc.
Exophthalmos is autoimmune but lid lag is adrenaline driven
what is grave’s disease
When autoimmune antibodies (TSI) bind and stimulate TSH receptor in thyroid ( agonists)
this causes overactive thyroid g
describe the thyroid gland in grave’s disease
Smooth symmetrical goitre , can hear whooshing blood flowing through it ( bruit) as v active . Diffuse enlargement of thyroid ( even enlargement)
What are some symptoms only found in grave’s disease
smooth goitre
Exophthalmos
Pretibial myxoedema ( non pitting aka not fluid accommodation caused by heart disease swelling of shins)
Why does exophthalmos occur in grave’s disease
Antibodies attacking muscles of eye
How do you preform a scintigram
thyroid gland takes up iodine – only gland in the whole body to do so
if you give small doses of radioactive iodine123 to the patient, you can image the thyroid
in Graves’ disease, as there is even growth of the thyroid, the thyroid scan (scintigram)
Why can’t do do thyroid scans on pregnant women and what must you do instead
Radiation can harm children
better to do blood test for thyrotropin receptor antibody ( trab)
what does grave’s disease look live on a thyroid scan
Uniform radioiodine uptake , aka thyroid gland of even proportions but enlarged
What is plummer’s disease
and what is it’s other name
aka toxic nodular goitre - a bit of the thyroid gland has become tumorous and is misbehaving (autonomous thyroxine production - no TSH stimulation)
What will happen to TSH in toxic nodular goitre
TSH will be low
what is a solitary toxic nodule
A toxic adenoma, whereby a single nodule undergoes hypertrophy
and produces excess thyroid hormones.
How to you treat plummers
surgery / removal via radioiodine
What will you see on toxic nodular goitre on a thyroid scan
Uneven distribution of size
Because there is too much thyroxine coming from the tumour part of the thyroid, the pituitary will stop making TSH and the normal part of the thyroid will slowly shrink and stop making thyroxine (suppressed by tumour)
This means that in the thyroid scan you will just see a hot nodule and the rest of the thyroid scan will not be seen
( aka will feel only on one side of neck(
What is viral thyroiditis or de quavrain’s
when a virus causes hyperthyroidism
Describe the mechanism of viral thyroiditis
acute inflammation of thyroid gland induced by viral infection
reduced thyroxine output, viral replication proceeds instead ( aka no thyroxine being made)
Stored thyroxine is released instantaneously from damaged thyroid follicles: Hyperthyroidism (1 month)
around four weeks, stored thyroxine is depleted: hypothyroidism
After another month, the cells will have recovered and will start to produce thyroxine again so they will return to normal
Patient then becomes euthyroid (normal functioning thyroid) again
What is special about viral thyroiditis
pateint will become hyperthyroid and then get hyperthyroidism ( due to depletion of T4 stores)
What will you see in terms of T4/TSH in viral thyroiditis
Low TSH , high free T4
