Chem Path: Thyroid Flashcards
Explain how TSH causes thyroxine (T4) production
TSH causes iodide uptake into the thyroid. Iodide is converted to iodine by thyroid peroxidase. Iodine is then taken into the cells via thryoglobulin. Iodine molecules are then joined together to form T4. T4 is released into the bloodstream and is then converted to T3 in the peripheries.
Apart from TSH what else helps with the uptake of iodide into the thyroid cells?
Na/K/ATPase pump
Which proteins is T4 bound to?
TBG, albumin
What is the cause of primary hypothyoridism?
thyroid gland itself
What is the cause of secondary hypothyoridism?
Pituitary
What are the 3 most common causes of hypothyroidism?
Hashimoto’s - autoimmune
Atrophic
Post Grave’s due to over treatment
Which drugs cause of hypothyroidism
amioderone
lithium
What are the clinical symptoms of hypothyroidism
Everything is slow and low
Hyponatraemia
Normocytic anaemia
What investigations for hypothyroidism
TSH and T4 levels Thyroid peroxidase anitbodies B12 levels for pernicious anaemia IgA Coeliac antibodies Early morning cortisol and adrenal antibodies for Addison's
Why would you do an ECG for hypothyroidism?
If they have underlying cardiac disease, giving them T4 can increase their myocardial contractility
What can excess T4 cause?
Osteopaenia and AF
What is subclinical hypothyroidism
Normal T4 but high TSH
What would you check for in subclinical hypothyroidism
TPO antibodies. If present, patient can develop thyroid disease
What is subclinical hypothyroidism associated with
Hypercholesterolaemia
How do thyroid levels change in pregnancy and why
HCG acts like TSH and causes a rise in T4
TBG levels also increase as they are under the influence of oestrogen
Later in pregnancy as HCG levels drop, so will T4 and therefore TSH will rise
Within how many hours of birth should the Guthrie test be done in a neonate and why?
48-72 hours
To avoid measuring maternal TSH
