Thyroid Flashcards
Thyroid lymphoma
a) risk factor
b) treatment
a) Hashimoto’s
b) Chemo (R-CHOP) and/or RT
Graves disease
a) Complications
a) - Thyroid eye disease
- Pretibial myxoedema
- Thyroid acropachy - clubbing, thickening
Thyroid antibodies
a) TSH-R
b) Anti-TPO
c) Anti-Tg
d) Which is implicated in hyperthyroidism of the newborn?
e) Which is implicated in thyroid eye and skin disease?
f) Which are implicated in cancer pathogenesis (e.g. breast)
g) Which are common in other autoimmune conditions?
h) Risk of thyroid antibodies in pregnancy?
a) 90% of GD, <20% HT, and 50% atrophic thyroiditis
b) 90% HT, 80% GD
c) 50% HT, 30% GD
d) Anti-TSH receptor
e) Anti-TSH receptor
f) Anti-TPO an Anti-Tg
g) Anti-TPO an Anti-Tg
- common in T1DM, coeliac, etc.
h) Anti-TPO or Tg - risk of preterm birth and miscarriage
Riedel’s thyroiditis
a) Presentation
b) Pathophysiology
c) Organs affected
d) Treatment
a) Generally painless goitre, progresses to cause obstructive symptoms (e.g. hoarseness, stridor, dysphagia).
O/E - hard “woody” thyroid, fixed to adjacent tissues, might be tender
b) Fibrosis and infiltration by IgG4 secreting plasma cells. Fibrosis can progress to involve adjacent tissues
c) Thyroid mainly + adjacent tissues
- Might also affect Pancreas, liver, kidneys, orbit, salivary glands if IgG4 disease
d) Prednisolone initially
May require surgery if airway obstruction or not responsive to steroids
Postpartum thyroiditis
a) Risk factors
b) Classical presentation
c) Differentials
d) Management
a) - Thyroid antibodies (anti-TPO and anti-Tg), rarely TSH-R
- Previous thyroid dx, previous postpartum thyroiditis, FHx
- T1DM or other autoimmune dx
b) - Painless thyroid
- Hyperthyroid phase 1-4 months post-partum lasting around 2 months
- Hypothyroid phase following this, lasting around 9-12 months
- Usually resolves completely within 18 months, but some women may remain hypothyroid
- Do not have eye disease (this would suggest Graves’)
c) - De Quervain’s/Riedel’s - tender thyroid, raised ESR
- Postpartum depression
d) - Beta-blockers for hyperthyroid phase (not anti-thyroid agents)
- Thyroxine may be used for hypothyroid phase if prolonged/severe symptoms/TSH >10
Causes of thyroid infiltration - TB-SMASH
TB
Sarcoidosis
Malignancy
Amyloidosis
Scleroderma
Haemochromatosis
Thyroid uptake scan
a) Thyroiditis vs Graves vs Nodules
a) - Thyroiditis: Poor uptake due to gland destruction
- Graves: diffuse good uptake
- Nodular: focal areas of uptake
Pharmacology
a) Carbimazole
b) PTU
c) Class they both belong to
a) Prevents TPO from iodinating thyroglobulin, hence reduces production of T3 and T4
b) Prevents conversion of T4 to T3
c) Thionamides
Radio-iodine
a) Indications
b) Contraindications
a) - Toxic nodule - best treatment
- Can be tried for Graves (not if TED)
b) Thyrotoxic state, thyroid eye disease, pregnant (or wanting to conceive in the next 6 months)
Anti thyroid drugs in pregnancy
a) Preference in each trimester
b) TFT target
c) If fails/neutropenia/etc –> alternative
d) Does thyroxine cross placenta
a) - PTU preferred in 1st trimester (but risk of hepato-toxicity in long-term use)
- Carbimazole has risk of cutis aplasia in first trimester
- Hence, often switched to carbimazole for 2nd/3rd trimester
b) - Lowest possible dose to maintain T3 and T4 at high end of normal
- TSH not reliable in pregnancy due to Beta HCG suppressing it
c) Thyroidectomy
- Optimal time is 2nd trimester
d) Thyroxine does not cross placenta but carbimazole/PTU do
Sick euthyroid syndrome
a) Causes
b) TFTs (vs hypothyrodism)
a) Unwell with e.g. infection, MI, trauma, etc.
b) - Low T3 +/- Low T4
- TSH is low, normal or only slightly elevated (in hypothyroidism, TSH will be significantly elevated)
Drugs that interfere with thyroid function
- Amiodarone - can cause hypothyroid via thyroiditis (more common)
or hyperthyroidism via iodine load especially in pre-existing thyroid disease - Lithium - inhibits thyroid iodine uptake, causing hypothyroidism
- CYP450 inducers - may reduce half life of T3/T4
- High dose steroids/dopamine - suppress TSH (cause secondary hypothyroidism)
- Oestrogens - increase thyroid binding globulins, reducing free T4 levels
Amiodarone induced thyrotoxicosis
a) Type 1 vs Type 2
b) Management
a) - Type 1 - occurs in those with pre-existing thyroid disease (e.g. Graves). Have normal iodine uptake on imaging and normal levels of IL-6, often with positive thyroid antibodies
- Type 2 - subacute thyroiditis in those without pre-existing thyroid Dx. Have reduced iodine uptake and elevated IL-6, with negative thyroid antibodies
b) - Carbimazole works well for type 1, steroids work well for type 2
- If cannot distinguish type 1 from type 2, treat with carbimazole + steroids
- Rapid response to carbimazole + steroids indicates probable type 2 (carbimazole should be tapered)
- Slow response indicates probable type 1 (steroids should be tapered)
Thyroid nodule
a) Malignancy and TFTs
b) Reasons to resect
c) FNA results
a) TFTs usually normal in malignancy (if abnormal in context of nodule, this is reassuring)
b) Elderly, >4cm, enlarging
c) 90% benign
10% malignant - mostly papillary (good prognosis)
Treatment of high cholesterol in patient with raised TSH
- Statins and fibrates can lead to increased risk of myalgia in patients with hypothyroidism
- Therefore, hypothyroidism (even subclinical) must always be adequately treated with levothyroxine prior to starting cholesterol-lowering therapy
