Thyroid disease Flashcards
Myxoedema coma.
a) Causes (2 main)
b) Features
c) Management
d) Mortality
a) Occurs mainly in the elderly, triggered by:
- Infections - UTI, pneumonia, sepsis, etc.
- Discontinuation of thyroid supplements
- Hypothermia
- Medication: amiodarone, lithium, beta-blockers
- Other stressors: MI, heart failure, trauma
- Rarely, first presentation of hypothyroidism
b) - Confusion, reduced GCS, seizures
- Hypothermia (< 35 C), features of hypothyroidism
- Hypoventilation, cardiac arrhythmias
c) - IV access - and bloods (raised TSH, low free-T4)
- IV thyroxine (switch to oral T4 when stable)
- IV hydrocortisone (often coexisting adrenal failure)
- May also use liothyronine (T3)
- Ventilation/ airway control
- ECG monitoring: ?prolonged QT
- Temperature control and warming measures
- Treat any precipitants (eg. infection)
d) 20 - 50%
Hypothyroidism.
a) Causes
b) Presentation - symptoms and signs
c) Investigations and findings:
- subclinical
- primary, secondary
- autoimmune
- who needs imaging?
a) Primary causes.
- Autoimmune (Hashimoto’s, De Quervain’s, post-partum)
- Congenital (agenesis/dysgenesis)
- Drug induced (carbimazole, PTC, amiodarone, lithium)
- Thyroid ablation / removal
Secondary/tertiary - low TSH/TRH
b) Symptoms.
- lethargy, intolerance to cold, dry skin, hair loss, impaired memory and concentration, constipation, decreased appetite with weight gain, reduced libido, menorrhagia/ oligomenorrhoea
- Signs: cool peripheries, bradycardia, dry/coarse skin, puffy face/hands/feet (myxoedema), goitre, delayed relaxation of deep tendon reflexes
c) - Subclinical: raised TSH, normal free-T4
- Primary: raised TSH, low free-T4
- Secondary: low TSH, low free-T4
- Autoimmune: raised TSH, low free-T4, anti-TPO or anti-thyroglobulin antibodies present (in 95%)
- USS thyroid gland if asymmetrical /nodular goitre
Hypothyroidism: management
a) Usual management, starting dose and titration?
b) Who should have a lower starting dose?
c) Subclinical hypothyroidism - treat or not?
d) Drugs that can interfere with thyroxine absorption
e) Monitoring
f) If non-response to treatment - management?
a) - Start oral levothyroxine at 50 - 100 mcg OD
- Titrate up by 25 - 50 mcg every 2-3 weeks according to response
- Monitor effects on TSH to normalise thyroid function
- Normal maintenance dose is 100 - 200 mcg OD
b) Start at 25 mcg in patients with:
CHD, severe hypothyroidism, age >50
c) - Risks of treating: increased fractures and AF risk
- Treat if: thyroid-antibody positive, previous thyroid disease (including hyperthyroid) or surgery, symptomatic, pregnant (in pregnancy, dose may need to be increased)
d) - Ferrous sulfate (take 2 hours apart), calcium supplements, rifampicin and amiodarone
e) Annual TSH monitoring once stable
f) - Consider non-compliance or interaction with medications like ferrous sulfate
- Consider secondary cause (eg. hypopituitarism)
Antibodies in thyroid disease.
a) Graves
b) Hashimoto’s
a) TSH receptor binding antibodies (99% sensitive, but not widely available); also often have anti-TPO and anti-thyroglobulin antibodies
b) Anti-TPO or anti-thyroglobulin (95%); TSH-receptor blockers
Thyroid malignancy.
a) Most common; women aged 30 - 40, usually presents early with local compression of trachea and laryngeal nerve; excellent prognosis
b) More common in iodine-deplete regions; greater propensity to metastasise to the lungs; requires an excisional biopsy to confirm
c) Arises from parafollicular calcitonin-producing C cells; CEA and calcitonin present in blood; may be part of MEN syndromes type 2A and 2B
d) Rapidly growing mass in the neck in woman with chronic Hashimoto’s thyroiditis
e) Rare aggressive tumour that presents in older age with hard mass and metastases; arises from follicular cells of the thyroid
f) Risk factors for thyroid malignancy
a) Papillary
b) Follicular
c) Medullary
d) Thyroid lymphoma
e) Anaplastic
f) - Radiation exposure
- Genetic syndromes - eg. MEN, FAP
- History of thyroiditis or goitre
Assessment of a thyroid mass.
a) Examination
b) Investigations
a) - Does it move with swallowing/tongue protrusion?
- smooth/diffuse (?goitre), nodular (MNG, malignancy)
b) Ix:
- Bloods: FBC, TFTs, ?antibodies,
- Imaging: USS first line (if nodular or asymmetrical)
- Special tests: may require FNA + biopsy
Hyperthyroidism.
a) Causes
b) Presentation - symptoms and signs (inc. eye signs)
c) Investigations
a) - Graves’ disease (75%)
- Toxic multinodular goitre
- Toxic thyroid adenoma
- Thyroiditis (eg. De Quervain’s - hyper, then hypo)
- Drug-induced: excess thyroxine, amiodarone, lithium
- Pituitary: TSH adenoma, pituitary resistance to T3/T4
b) - Symptoms: weight loss despite increased appetite,
irritability, weakness, fatigue, diarrhoea (± steatorrhoea),
sweating, heat intolerance, tremor, palpitations, anxiety, psychosis, loss of libido, oligo/amenorrhoea, visual symotoms (thyroid eye disease)
- Signs: clammy hands, palmar erythema, tremor, tachycardia (?AF), goitre, proximal muscle wasting,
clubbing (thyroid acropachy), pretibial myxoedema (thyroid dermopathy; often following trauma) - Eye signs: exophthalmos, lid retraction, ophthalmoplegia, chemosis
c) - Bloods: CRP/ESR (may be raised in thyroiditis), TFTs (typically, low TSH, raised free-T4)
- Antibodies: anti-TPO and anti-thyroglobulin (not specific - also present in Hashimoto’s); anti-TSH (specific but not widely available)
- Imaging: USS thyroid, thyroid uptake scan (can show hot and cold spots - malignancy or TMG)
Hyperthyroidism: management
a) Initial management
b) Anti-thyroid medication
c) Side effects of anti-thyroid medication
d) Two different strategies with anti-thyroid medication
e) Monitoring and dose reduction
f) Radio-iodine: indications and contraindications
g) Surgery: indications and complications
a) - Refer to specialist.
- Symptom control while awaiting definitive treatment
(Beta-blockers: propanolol)
b) Anti-thyroid medication.
- 1st line: carbimazole
- 2nd line: propylthiouracil (PTU)
c) Side effects.
- Nausea and a bitter taste after taking medication
- Severe: agranulocytosis (beware: sore throat, rash, etc)
- PTU - can cause liver failure
d) Regimens.
- “Block and replace” - anti-thyroid drugs are given with thyroxine replacement
- “Dose titration” - anti-thyroid drug only, titrated up (generally fewer side effects)
e) Monitoring.
- TSH unreliable; use free-T4 and symptoms
- Once euthyroid, begin reducing anti-thyroid drug dose
- Remission usually after ~ 18 - 24 months, then can attempt stopping anti-thyroid drug entirely
f) Radio-iodine.
- Indications: failure of anti-thyroid drugs, relapse, 1st line in teenagers; 1st line in subclinical hyperthyroidism
- Contraindications: pregnancy, breastfeeding, thyroid eye disease
g) Surgery (subtotal thyroidectomy).
- Indications: failure of anti-thyroid drugs and radio-iodine, especially in pregnancy and thyroid eye disease, obstructive goitre (airway compromise)
- Must be euthyroid pre-surgery to avoid thyroid storm
- Complications: haemorrhage, infection, hypothyroid, hypoparathyroid, vocal cord paralysis
Thyrotoxic storm.
a) Causes/triggers
b) Presentation
c) Investigations
d) Management
a) Usually known thyrotoxic patient, with:
- Intercurrent illness (infection, MI, stroke, PE, DKA)
- Withdrawal of anti-thyroid drugs
- Recent thyroid surgery
- Other stress: trauma, emergency surgery, etc.
b) - Symptoms: sweating, nausea, vomiting, jaundice, diarrhoea, abdominal pain, confusion, seizures, coma
- Signs: hyperpyrexia (> 41°C), tachycardic (> 140) +/- AF or other arrhythmia, hypotension, congestive heart failure, dehydration
c) - Bloods: FBC, CRP, ?septic screen,
- TFTs - should have raised T4, low TSH
- ECG important - tachy, arrhythmias (eg. AF)
d) - If suspected, start treatment before getting TFT results
- Treat underlying cause (eg. infection)
- A-E assessment - oxygen, ventilation, fluids, etc.
- Oral antithyroid drugs: propylthiouracil > carbimazole
- 8 hours later: Lugol’s solution (iodine therapy)
- Beta-blockers (propanolol)
- Cooling measures - paracetamol, fans, tepid sponging
