Chem path 9s - Thyroid Flashcards
What does TSH control the uptake of?
Iodide
What blocks TSH?
Perchlorate
Normal thyroxine hormone synthesis?
Iodide taken up by thyroid cells Iodide --> iodine by TPO (Thyroid peroxidase) Iodine is taken up by thyroglobulin Converted to MIT, DIT and T3 and T4 In peripheries T4 --> T3
T3 and T4- how does it travel in circulation?
Free and active (0.03%)
Bound to TBG (majority)
Bound to thyroxine-binding pre albumin (TBPA)
Bound to albumin
What is Reidel’s thyroiditis associated with?
Hypothyroidism and IgG4 related disease
What other hormone can stimulate the same actions as TSH?
bHCG
Most hypothyroidism is…
PRIMARY
What antibodies are found in Hashimotos?
Anti-TPO and Anti-TG
Main Causes of hypothyroidism
Hashimoto’s
Atrophic thyroid (diffuse lymphocytic infiltration and atrophy, no goitre or antibodies)
Post-graves
What drugs can cause hypothyroidism classically?
PTU/CBZ + Amiodarone + lithium
Which other autoimmune conditions could be associated with Hashimotos?
Pernicious anaema, coeliac, Addisons
High TSH + Low T4
Primary hypothyroidism
Management of hypothyroidism?
ECG
T4 (titrate to a normal TSH)
High TSH Normal T4
Subclinical hypothyroidism or treated hypothyroidism
What is sublinical hypothyroidism?
High TSH and normal T4 (body wrongly thinks T4 levels are low)
Predictor for future primary hypothyroidism, esp if anti-TPO is present
What other condition is HYPOthyroidism associated with?
Hypercholesterolaemia (this is the only benefit of treating sublinical hypothyroidism)
T4 in first trimester
Rise in hCG causes slight rise in free T4
t4 in 3rd trimester
hCG levels drop, T4 levels drop too and slight increase in TSH
What other thyroid hormone increases during pregnancy?
TBG
Initially high TSH then low TSH, low T3 and T4
Sick euthyroidism
What is sick euthyroidism?
if you are very sick, the thyroid may shut down to try and reduce the basal metabolic rate to conserve energy (however, there are NO hypothyroid symptoms)
3 main cause of hyperthyroidism
1) Graves
2) Toxic multinodular goitre
3) Single toxic adenoma
What will the 3 main causes of hyperthyroidism show on technetium scan?
HIgh uptake
Post-partum thyroiditis on technetium scan
LOW uptake
