Chemical Pathology - Thyroid Flashcards
1
Q
how is thyroxine produced?
A
- iodide goes through membrane from capillary via Na/K ATPase
- iodide to iodine by thyroid peroxidase
- iodine taken up by thyroglobulin
- iodination of tyrosine residues in thyroglobulin = MIT and DIT
- T4 produced and stored in thyroid gland
2
Q
what happens to T4 in periphery?
A
converted to T3
3
Q
to what 3 proteins does T4 bind to?
A
TBG
TBPA (thyroid binding pre albumin)
Albumin
4
Q
antibodies in Hashimoto’s/ chronic lymphocytic thyroiditis
A
anti-TPO
anti-TG
5
Q
antibodies in Grave’s
A
anti-TSH
anti-TPO
6
Q
antibodies in Reidel’s thyroiditis
A
IgG4 related disease
7
Q
antibodies in Viral thyroiditis
A
NO ANTIBODIES
hyperthyroid to hypothyroid
8
Q
main 3 causes of hypothyroidism?
A
- Hashimoto’s (AI)
- atrophic thyroiditis
- Post-Grave’s disease (radioactive iodine, surgery, thionamides)
9
Q
other minor causes of hypothyroidism?
A
- post-thyroiditis
- thyroid agenesis/dygenesis
- 2nd hypothyroidism (pituitary disease)
- drugs (amiodarone, lithium)
- iodine deficiency
- peripheral thyroid hormone resistance
10
Q
clinical features of hypothyroidism
A
- weight gain
- bradycardia
- constipation
- laboured breathing
- oligomenorrhoea
- poor appetite
- hyponatraemia
- cold/dry hands and feet
- normocytic anaemia
11
Q
Investigations in hypothyroidism
A
- high TSH
- low T4
- TPO antibodies
- consider presence of other AI conditions
12
Q
Tx in hypothyroidism
A
- perform ECG (levothyroxine will exacerbate MI and worsen HF)
- Levothyroxine (titrate to normal TSH)
- Liothyronine
13
Q
what is subclinical hypothyroidism?
A
- T4 level is normal, TSH is high
- TPO antibodies are positive, suggests pt may go on to develop thyroid disease
- unlikely to be cause of presenting symptoms
14
Q
what is hypothyroidism associated with?
A
hypercholestrolaemia
15
Q
what is a risk of radioiodine tx?
A
hypothyroidism
normally occurs within 1 year
