Thyroid Flashcards
Hypothyroidism causes
Mostly primary - either Hashimoto’s (AI) or atrophic
- Distinguish on Abs + goitre
Occasionally iatrogenic post-hyperthyroid, hypopituitarism, iodine deficiency, drugs (amiodarone, lithium, carbimazole)
Low T3/T4, high TSH
Anti-TPO + Anti-TBG antibodies
Goitre
Hashimoto’s
Low T3/T4, high TSH
No antibodies
No goitre
Atrophic thyroid (lymphocytes infiltrate + destroy)
Why is it important to do the Guthrie spot test at 5-8 days?
One of the things Guthrie spot tests for is congenital hypothyroidism (using TSH levels)
Too early - maternal TSH distorts
Too late - intellectual disability
Hyperthyroidism causes
Distinguish using Technetium uptake scan
- High uptake - Graves’ (40-60%), Toxic multinodular, Single toxic adenoma
- Low uptake - Thyroiditis (initial stages)
Rarer causes: TSH-oma of pituitary, thyroid cancer, trophoblastic disease (B-hCG acts like TSH)
High T3/T4
Anti-TSHr antibodies (pre-tibial myxoedema, exopthalmos)
Smooth diffuse goitre
DIffuse whole gland uptake scan
Graves’ disease
High T3/T4
Hyperplasia following hypothyroid period
Multiple hot nodules on uptake scan
Toxic multi-nodular
High T3/T4
Single hot spot on uptake scan
Single toxic adenoma
High T3/T4 Hx pregnancy / viral illness Painful goitre No uptake Become hypothyroid
Initial stages of thyroiditis (either post-partum or viral ‘de Quervain’s aka sub-acute)
Later will become hypothyroid as they have released all thyroid hormone
Tx hypothyroidism
T4 (levothyroxine)
Tx hyperthyroidism
B-blocker to keep safe
If low uptake - NSAIDs (self-limiting)
If high uptake (thionamides e.g. carbimazole, propylthiouracil; radioactive I2, surgery)
Problem with thionamides
Agranulocytosis
Raised TSH
Normal T4
Subclinical hypothyroidism
(like pre-hypothyroid)
Presence of TPO Ab predicts likelihood of developing
Low T3/T4
TSH high then low
No hypothyroid symptoms
Sick euthyroidism
Occurs in severe illness
What happens to thyroid hormones in pregnancy?
1st trimester - high B-hCG acts like TSH and increases T3/T4
2nd/3rd trimester - B-hCG falls and T3/T4 fall back to normal
Most common thyroid cancer
Psammoma bodies
Good prognosis
Papillary
Thyroid cancer linked to Hashimoto’s
Lots of proliferating lymphocytes
Lymphoma
Thyroid cancer
Well differentiated but spreads early
Follicular
Thyroid cancer C-cells produce calcitonin CEA + calcitonin tumour markers Linked to MEN2 Rare but devastating
Medullary
Thyroid cancer
Elderly, appalling prognosis
Anaplastic
4 key stages of thyroid cancer Tx
- Total thyroidectomy
- Zap out remaining cells with radioactive iodine
- Supraphysiological doses of thyroxine - to suppress TSH (tumours very sensitive to TSH)
- Monitor thyroglobulin as tumour marker
What is monitored after thyroid cancer treatment to check for recurrence?
Thyroglobulin
Inheritance pattern MEN
AD
‘MEN Are Dumb’
MEN1
3Ps
Pituitary, pancreatic (insulinoma), parathyroid (hyperparathyroidism)
