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
Tx for hypothyroidism? precautions?
Levothyroxine (dose depends on weight)
Must do ECG (excess T4 = risk of AFib and osteopenia)
top 3 causes of hyperthyroidism?
1) Graves disease
2) toxic multi nodular goitre
3) toxic adenoma
Graves disease - M/F? what type of hyperthyroidism? Cause? presentation?
F:M is 9:1! High uptake on technetium scan Anti-TSHR and anti-TPO Wt loss, diarrhoea, dysmenorrhea, tremor Exophthalmos, pretibial myxoedema, acropachy
3 causes of high uptake hyperthyroidsm
1) Graves disease
2) toxic multi nodular goitre
3) toxic adenoma
2 causes of low uptake hyperthyroidism
1) subacute dequiervan’s thyroiditis
2) post partum thyroiditis
Features of subacute dequervain’s thyroiditis.
TFTs?
Post-viral
Painful goitre!!!
Initially hyperthyroid, then hypothyroid
Important Ix in suspected hyperthyroidism
TFTs Technetium scan Anti-thyroid antibodies Screen for autoimmune antibodies ECG for concurrent AFib Bone mineral density
Treatment for high uptake hyperthyroidism?
Beta blockers
CBZ or PTU = to block and replace, or titrate
Consider radio iodine and surgery
When not to use radio iodine?
If Graves disease with exophthalmos, radio-iodine can make things worse!!
Treatment for low uptake hyperthyroidism?
Beta blockers
NSAIDs for De Quervain’s thyroiditis
Precautions with PTU and Carbimazole?
1% develop agranulocytosis
warn patients to seek HCP if fever/sore throat
Titrate dose for 18 months
3 types of thyroid cancer? most common?
Papillary - most common
Follicular
Medullary
Histology and prognosis for most common type of thyroid cancer?
Papillary thyroid cancer
- Psammoma bodies
- v good prognosis!
mx of thyroid cancer
Surgery (thyroidectomy)
+/- Radioiodine
Thyroxine (to suppress TSH)
Medullary thyroid cancer
- what is it linked to?
- which Ix must you do
linked to MEN2 (phaeo + parathyroid cancer)
- calcitonin and CEA levels
