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
