Chempath - Thyroid Flashcards
High TSH, Low T4?
Primary hypothyroidism
High TSH, normal T4?
Treated hypothyroidism or subclinical hypothyroidism
High TSH, high T4?
TSH secreting tumour
Low TSH, High T4
Primary hyperthyroidism
Low TSH normal T4
subclinical hyperthyroidism
Low TSH, low T4
central hypothyroidism
Initially high TSH then low TSH, low T3, low T4
Sick euthyroidism
Normal thyroxine hormone synthesis?
- iodine absorbed from GIT and converted to I-
- I- is taken up by thyroid cells
- I- –>I2 by TPO
- I2 is taken up by thyroglobulin
- Converted to MIT, DIT, T3 and T4
- T3 and T4 are transported to capillary lumen
T3 and T4 - how does it travel in the circulation?
Bound mostly to proteins - TBG, TBPA and albumin
0.03% is free and active!
Top 3 causes of hypothyroidism?
- Primary atrophic hypothyroidism
- Hashimoto’s thryoiditis
- Post thyroidectomy/radioiodine
Hashimoto’s thyroiditis - what is it? epidemi?
- anti-TPO antibodies –> goitre + plasma cell infiltration of thyroid
- Elderly females.
Drugs which induce hypothyroidism?
PTU/CBZ
Lithium
AMiodarone
WTF is subclinical hypothyroidism
High TSH and normal T4 (body wrongly thinks T4 levels are low)
Predictor for future primary hypothyroidism, esp if anti-TPO is present
WTF is sick euthyroidism? presentation?
A physiological response to severe illness - the thyroid shuts down to reduce basal metabolic rate
Asymptomatic
Ix done in suspected hypothyroidism?
TFTs
anti-thyroid antibodies
ECG - as tx can cause MI
Screen for other autoimmune conditions