Endocrine - Thyroid

Question 1

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

Answer 1

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

Question 2

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

Answer 2

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

Question 3

What are causes of goitre + hyperthyroidism?

Answer 3

Grave’s, Benign Thyroid neoplasms

Question 4

What are causes of goitre + hypothyroidism?

Answer 4

Hashimoto’s Thyroiditis, Iodine Deficiency (thyroid compensates by enlarging to increased iodine uptake), De Quervain’s Thyroiditis (subacute thyroiditis)

Question 5

What are the thyroid eye signs?

Answer 5

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

Question 6

What are the complications of hyperthyroidism?

Answer 6

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

Question 7

What are the causes of hyperthyroidism?

Answer 7

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)

Question 8

What are the causes of hypohyroidism?

Answer 8

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

Question 9

What are the differentials for a solitary nodule of a thyroid mass?

Answer 9

• Dominant nodule of MNG
• Follicular adenoma
• cyst
• carcinoma

Question 10

What are the differentials for a thyroid mass that is diffusely enlarged?

Answer 10

Hyperthyroid: Graves

Non toxic (hypothyroid/ euthyroid): lymphoma, Hashimoto’s thyroiditis, subacute thyroiditis

Question 11

What are the differentials for a multinodular goitre?

Answer 11

Hyperthyroid: toxic MNG

Hypothyroid: Hashimoto’s thyroiditis

Question 12

How do you approach a thyroid nodule?

Answer 12

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

Question 13

What is the treatment of hot thyroid nodule?

Answer 13

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

Question 14

What are the investigations performed for hyperthyroidism/ hypothyroidisim?

Answer 14

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

Question 15

What is the treatment of hyperthyroidism?

Answer 15

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)

Question 16

What are the side effects to Anti-thyroid Medication (thionamides)?

Answer 16

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

Question 17

What is the counselling required for Radioiodine?

Answer 17

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

Question 18

What are the indications of thyroidectomy: partial or total (w/ thyroxine replacement)?

Answer 18

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

Question 19

What are the risks of thyroidectomy?

Answer 19

Damage to parathyroids: may lead to transient hypocalcaemia

Recurrent laryngeal N injury 🡪 hoarseness of voice

Life-long thyroxine

Question 20

What are the clinical features of thyroid storm?

Answer 20

• 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)

Question 21

What is the Burch- Wartosky score?

Answer 21

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

Question 22

What are the precipitants of a thyroid storm?

Answer 22

• 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

Question 23

What are the investigations to be performed for thyroid storm?

Answer 23

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

Question 24

What is the management of a thyroid storm?

Answer 24

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

Question 25

In what groups of patients is myxedema coma a possible differential

Answer 25

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

Question 26

What are the neurological features of myxoedema coma?

Answer 26

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)

Question 27

What are the CVS features of myxoedema coma?

Answer 27

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

Question 28

What are the respi features of myxoedema coma?

Answer 28

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

Question 29

What are the metabolic features of myxoedema coma?

Answer 29

Hypothyroidism leads to increased ADH secretion 🡪 Hyponatremia Hypoglycaemia

Question 30

What are the renal features of myxoedema coma?

Answer 30

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

Question 31

What are the GI features of myxoedema coma?

Answer 31

Gastric atony, impaired peristalsis, paralytic ileus from mucopolysaccharide infiltration and edema of the muscularis Ascites GI bleeding from associated coagulopathy

Question 32

What are the hematological features of myxoedema coma?

Answer 32

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

Question 33

What is the maagement of myxoedema coma?

Answer 33

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

Question 34

What are the causes of hypotension in a patient with myxoedma coma?

Answer 34

Hypotension: sepsis, MI, pericardial effusion, occult bleeding, adrenal insufficiency (important to rule out before starting thyroxine replacement!!)