Endocrine - Thyroid Flashcards
What are the clinical features of hyperthyroidism?
- Temperature intolerance
- Appetite changes
- Weight changes
- Bowel habit changes
- Changes in sympathetic discharge
- Changes in skin and nails
- Changes in mood
- Eye problems
- Other systemic signs
Heat intolerance
Polyphagia (↑Appetite)
Weight loss
Diarrhoea, increased bowel movements
Increased sweating, Palpitations
Dry, scaly skin, Onycholysis (Graves’)
Changes in mood
- Nervousness, Insomnia
- Irritability
- Hyperactivity
Eye problems
- Double vision
- Redness
- Pain
Other systemic signs
- Muscle weakness: cannot climb stairs, comb hair
- Exertional dyspnoea: CCF
- Insomnia
- Pretibial Myxoedema (only in grave’s)
- Amenorrhea
What are the clinical features of hyporthyroidism?
- Temperature intolerance
- Appetite changes
- Weight changes
- Bowel habit changes
- Changes in sympathetic discharge
- Changes in skin and nails
- Changes in mood
- Eye problems
- Other systemic signs
Cold intolerance
Decreased appetite
Weight gain
Constipation
Lethargy
Coarse, pale, dry
Xanthoma (hyperlipidemia)
Changes in mood
- Mental, physical sluggishness
- Depression
- Poor memory
Eye problems
- Odema of eyelids
- Xanthalesma (hyperlipidemia)
Other systemic signs
- Hoarse voice
- Hypercarotenamia
- Leg swelling (myxoedema)
- Menorrhagia
What are causes of goitre + hyperthyroidism?
Grave’s, Benign Thyroid neoplasms
What are causes of goitre + hypothyroidism?
Hashimoto’s Thyroiditis, Iodine Deficiency (thyroid compensates by enlarging to increased iodine uptake), De Quervain’s Thyroiditis (subacute thyroiditis)
What are the thyroid eye signs?
Bulging eyes (exopthalmos) 🡪also causing Pain, Inability to close eyelids
Upper eyelid retraction: you can see the upper limbus which is ABNORMAL
Lid lag on downward gaze: due to retraction
Conjunctivitis
Ophthalmoplegia: Affects in order Inferior R 🡪 Medial R 🡪 Superior R 🡪 Lateral R
Diplopia – due to swollen extraocular muscles, ask esp when looking down
Vision Changes – due to compression on optic nerve
What are the complications of hyperthyroidism?
Compression (usually if malignant): Stridor / Dyspnoea, dysphagia, syncope
Invasive (for thyroid cancer)
Signs of heart failure & A Fib: due to hyperthyroid
Recent fragility fractures from osteoporosis due to Hyperthyroidism
What are the causes of hyperthyroidism?
Grave’s disease
Toxic multinodular goiter/ toxic adenoma
Thyrotoxic phase of Hashimoto’s or postpartum thyroiditis
Thyrotoxic phase of Subacute (de Quervain) granulomatous thyroiditis – preceding URTI
Subacute lymphocytic thyroiditis
Exogenous
Pregnancy (hCG)
Testicular germ cell tumour (hCG)
Hydatidiform mole/ choriocarcinoma (hCG)
What are the causes of hypohyroidism?
Autoimmune thyroiditis
- Hashimoto’s
- Postpartum
- Riedel (IgG4 secreting plasma cells)
- Atrophic (no goiter)
Drugs
- Carbamazepine
- Lithium: “any mood drugs?”
- Amiodarone
- Phenytoin
Iodine deficiency e.g. in pregnancy
Dyshormonogenesis
Subacute (de Quervain) thyroiditis
What are the differentials for a solitary nodule of a thyroid mass?
- Dominant nodule of MNG
- Follicular adenoma
- cyst
- carcinoma
What are the differentials for a thyroid mass that is diffusely enlarged?
Hyperthyroid: Graves
Non toxic (hypothyroid/ euthyroid): lymphoma, Hashimoto’s thyroiditis, subacute thyroiditis
What are the differentials for a multinodular goitre?
Hyperthyroid: toxic MNG
Hypothyroid: Hashimoto’s thyroiditis
How do you approach a thyroid nodule?
1) Examine Thyroid Status 🡪 Thyroid function test to assess fT4, TSH
- To assess if nodule is a/w HyperT, HypoT, EuT (not necessarily causing it)
- Majority of pt with thyroid nodules are euthyroid!
2) Examine the Nodule 🡪 Thyroid USS; more likely Malignant if:
- Tall & Thin on transverse scan
- Increased internal vascularity (via doppler US)
- Irregular Edges
If diffusely enlarged 🡪 confirm w/ USS 🡪 proceed w/ Auto-Ab testing
If nodule 🡪 proceed with step
3) Iodine Uptake Scan 🡪 to assess if Hot or Cold Nodule!
- Hot Nodule aka a TOXIC nodule causing massive fT4 release (and hence low TSH). Does NOT require Biopsy, toxic thyroid nodules tend to be indolent and less aggressive
- Cold Nodule: Nodule is inactive and does not produce T4. Require biopsy to determine if nodule is Thyroid / secondary tumor! If pt with cold nodule is hyperT 🡪 may indicate a separate aetiology
4) Biopsy via FNAC: Bethesda Classification
What is the treatment of hot thyroid nodule?
Treat with uni/bilateral Thyroidectomy OR Radioactive Iodine treatment
Radioactive Iodine treatment may leave pt Hypothyroid for the rest of his life, requiring Thyroxine supplementation
What are the investigations performed for hyperthyroidism/ hypothyroidisim?
Thyroid panel
- Thyroid stimulating hormone
- Free Thyroxine (T4)
Antibodies
- Graves’: TRAb (TSH Receptor Ab) / TSI (Thyroid Stimulating Immunoglobulins)
- Hashimoto’s: TPO Ab (Thyroid Peroxidase Ab) / TG Ab (Thyroglobulin Ab)
US thyroid – to assess nodularity / diffuse swelling. Not required to Dx grave’s if there is PE findings & +ve Ab
Radioiodine uptake scan – more so for nodules to assess if hot / cold
FNAC
What is the treatment of hyperthyroidism?
Symptom control
- Beta-blockers i.e. atenolol 25-50mg/day
- Alternative to BB: CCB (eg: Diltiazem)
Anti-thyroid Medication (thionamides) 🡪 inhibits thyroid hormone synthesis
- E.g. Carbimazole, Propylthiouracil (PTU) 🡪 Block & Replace approach
Radioiodine (RAI): Will need Lifelong thyroid hormone replacement
Surgical aka thyroidectomy: partial or total (w/ thyroxine replacement)
What are the side effects to Anti-thyroid Medication (thionamides)?
Agranulocytosis (0.5%), cross-reactivity between 2 drugs
- Emphasis on the importance of regular blood tests
- Advise if fever/sore throat/mouth ulcers to stop, check WCC
Propylthiouracil preferred in pregnancy (T1) as carbimazole is teratogenic (C/I in T1)
Hepatotoxicity: Carbimazole less hepatotoxic, longer half-life
What is the counselling required for Radioiodine?
Will need Lifelong thyroid hormone replacement
Contraindicated in breastfeeding / pregnancy and avoid for 6M to 1Y
Thyroid Eye Disease is a RELATIVE CONTRAINDICATION – RAI will worsen the eye disease; however we can provide steroids to prevent this
Ask if staying at home w/ pregnancy women / young children 🡪 radiation exposure through contact / urine is bad for them. Cannot hug them, cannot even share the same toilet
What are the indications of thyroidectomy: partial or total (w/ thyroxine replacement)?
Relapse despite pharmacological therapy
Cosmesis
Development of thyroid eye signs, compressive symptoms : 1st line for pt w/ TED is Surgery, however RAI is still possible w/ steroids if Surgery is C/I
Cancer
What are the risks of thyroidectomy?
Damage to parathyroids: may lead to transient hypocalcaemia
Recurrent laryngeal N injury 🡪 hoarseness of voice
Life-long thyroxine
What are the clinical features of thyroid storm?
- Pyrexia (Fever): very severe if >40 degrees
- Tachycardia
- Neurological Dysfunction (Restlessness -> Agitation -> Psychosis -> Seizures -> Coma)
- Cardiovascular Dysfunction (A Fib, Heart Failure)
- GI Dysfunction (N&V, Diarrhoea, Abdominal Pain, Jaundice)
What is the Burch- Wartosky score?
Components (same as the characteristic clinical features)
- Thermoregulatory
- CNS: mental state
- GI
- CVS (Tachycardia, AF)
- CCF
Interpretation of score!
- 45 and above = highly suggestive
- 25-44 = supports
- <25 = unlikely thyroid stor
What are the precipitants of a thyroid storm?
- Infection (Most Common)
- Infarction / CVA / CCF / DKA / Trauma
- Recent thyroid surgery
- Radioiodine Therapy (RAI)
- Non-Thyroid Sx in pt w/ inadequately controlled HyperT or undiagnosed HyperT
- Sudden withdrawal of antithyroid medication
- Administration of iodinated contrast
What are the investigations to be performed for thyroid storm?
ABCs
Bloods
- FBC, Renal Panel, LFT, FT4, TSH, CBG
- Septic Workup (a DDx for thyroid storm + to elucidate aetiology for thyroid storm)
Imaging
ECG – for AMI
CXR – for CCF
What is the management of a thyroid storm?
Beta-blocker if patient in severe tachycardia (>170 bpm will compromise CO): Propanolol 40-80mg 6-8 hourly or Esmolol (faster acting + cardioselective 😊)
Inhibition of new thyroid hormone synthesis: PTU 400-600mg stat then 200mg 4-6H or Carbimazole 30mg BD-QDS
- However PTU has S/E of hepatotoxicity (will worsen the liver damage in Thyroid Storm)+ CMZ is faster acting, hence CMZ the preferred choice
Inhibition of thyroid hormone release (after inhibiting synthesis)
- Lugol’s iodine 4-8 drops 6-8hourly (Wolff-Chaikoff effect)
- Given 1 hour after CMZ – if given before, iodine may be used by thyroid to produce more thyroid hormones
Inhibition of peripheral T4 to T3 conversion: Steroids i.e. IV hydrocortisone 50-100mg 6-8H for 24-36 hours
Removal of excess thyroid hormones : Cholestyramine – removal through enterohepatic circulation
Treat the underlying trigger
In what groups of patients is myxedema coma a possible differential
Consider in all comatose patients with at least one of the following:
- Hypothermia
- Hyponatraemia: Hypothyroid leads to increased ADH secretion
- Hypercapnia: reduced respiratory drive (due to CNS depression) 🡪 Hypercapnia
Coma is a misnomer: patients usually present with cognitive deterioration (confusion, lethargy, disorientation), does not necessarily require a comatose state
What are the neurological features of myxoedema coma?
Hypothermia AND Unconsciousness are the 2 cardinal signs
OR Cognitive Deterioration: Include disorientation, depression, paranoia, hallucinations, cerebellar signs, poor memory and recall, abnormalities on EEG (low amplitude and decreased rate of alpha activity), seizures (up to 25% due to low sugars, hypoNa, hypoxemia)
What are the CVS features of myxoedema coma?
Impaired cardiac contractility & HR leading to reduced stroke volume and cardiac output 🡪 Hypotension, Bradycardia
Pericardial effusion from accumulation of fluid in mucopolysaccharides within the pericardial sac
What are the respi features of myxoedema coma?
Hypoventilation and Hypercapnia (and hypoxia) due to depressed hypoxic respiratory drive and a depressed ventilatory response to hypercapnia 🡪 respiratory acidosis
Partial obstruction of the upper airway caused by edema of the tongue or vocal cords contributes too 🡪 requiring ventilation
Tidal volume may be reduced by pleural effusion and ascites
What are the metabolic features of myxoedema coma?
Hypothyroidism leads to increased ADH secretion 🡪 Hyponatremia
Hypoglycaemia
What are the renal features of myxoedema coma?
Decreases in GFR and renal plasma flow, and increases in total body water
Atony of the urinary bladder with retention of large residual urine volumes
Renal failure from rhabdomyolysis
What are the GI features of myxoedema coma?
Gastric atony, impaired peristalsis, paralytic ileus from mucopolysaccharide infiltration and edema of the muscularis
Ascites
GI bleeding from associated coagulopathy
What are the hematological features of myxoedema coma?
Thrombosis in mild hypothyroidism
Bleeding in severe hypothyroidism due to an acquired von Willebrand syndrome (reversible with thyroxine) and decreases in factors V, VII, VIII, IX, X.
Bleeding may also be due to DIC from sepsis
What is the maagement of myxoedema coma?
Airway protection with mechanical ventilation: Usually required for the first 36-48 hours, but may need to continue assisted ventilation for as long as 2-3 weeks
Frequent ABGs to ensure adequate oxygenation and correction of hypercapnia
Fluid management
- Supplement in severe hypotension vs restriction for hyponatremia
- Provide 0.9% NS w IV Dextrose (for Hypotension, HypoNa and Hypoglycemia)
Hypothermia: Minimally invasive central rewarming
- Airway rewarming with humidified oxygen at 40 degrees
- IV fluids heated to 40 degrees
- Watch for hypoglycemia as rewarming may unmask hypoglycemia
- Rewarm slowly, rapid rewarming can precipitate an arrhythmia
Specific Treatment
- Thyroid replacement with both T3 (triiodothyronine and T4 (levothyroxine)
- High-dose glucocorticoid therapy until coexisting adrenal insufficiency can be excluded
What are the causes of hypotension in a patient with myxoedma coma?
Hypotension: sepsis, MI, pericardial effusion, occult bleeding, adrenal insufficiency (important to rule out before starting thyroxine replacement!!)
