Chemical pathology - Thyroid Flashcards
What % of T4 is typically bound to TBG?
75%
To which proteins can T4 bind?
TBG
TBPA
Albumin
Recall 6 possible aetiologies of primary hypothyroidism
Hashimoto’s
Atrophic (1st in UK)- no goitre, small thyroid due to lymphocytic infiltration
Lihtium, Amiodarone
Iodine deficiency (1st worldwide)
Riedel’s thyroiditis = dense fibrosis, stony hard
Post thyroidectomy/radioiododine
What is the expected TSH and T4 levels in primary hypothyroidism?
TSH high
T4 low
What test should always be done before thyroid-replacement medication is initiated?
ECG - because T4 increases cardiac contractility
How does thyroid function change in pregnancy?
In 1st trimester, there is a huse rise in hCG
hCG has the same configuration as TSH - this then stimulates the thyroid gland to produce supra-physiological amounts of thyroxine
However, this is normal in pregnancy, so the woman doesn’t become clinically hyperthyroid
What type of non-thyroid malignancy can cause thyrotoxicosis?
Malignancy that produces hCG
What test is used to detect neonatal hypothyroidism?
Guthrie test on day 2/3 of life
What does the term ‘sick euthyroid’ refer to?
Any severe illness –> reduced T4, increased TSH and decreased T3
This is normal physiology in sepsis
Recall 5 differentials for the cause of hyperthyroidism, and how each would appear on a technetium scan
- Grave’s (40-60% of cases) - high uptake
- Toxic multinodular goitre (30-50%) - high uptake
- Single toxic adenoma - high uptake
- Subacute de quervain’s thyroiditis - low uptake
- Postpartum thyroiditis - low uptake
What drugs can be used to treat an overactive thyroid? What is their mechanism of action?
Carbimazole and propylthiouracil
Inhibit thyroid peroxidase
What is the main risk of carbimazole and propylthiouracil treatment?
Agranulocytosis
- if sore throat or fever, stop testament and seek advice
Over how long should carbimazole and propylthiouracil treatment be titrated ?
18 months
How should papillary thyroid Ca be treated?
Removal of thyroid gland
Then radioiodine treatment
Then give supraphysiological thyroxine (so Ca cells not reactivated)
Recall 2 tumour markers for medullary thyroid cancer
CEA and calcitonin
Which type of thyroid cancer is associated with Men II?
Medullary
is T3 or T4 active? which is more abundant
T3 = active T4 = abundant
is the TSH high or low in subclinical hypothyroidism
TSH = high but T4 is NORMAL
TSH and T4 levels in hyperthyroidism
low TSH
high T3 and T4
what cell is associated w Hashimoto’s
hurthle cell
solitary hot nodule on isotope scan =
toxic adenoma
initially hyperthyroid, then hypothyroid =
de quervain’s thyroiditis - self limiting, post viral painful goitre
what’s Plummer’s disease
toxic multi nodular goitre = painless goitre
what psychiatric drug commonly causes hypothyroidism
lithium
