Investigation

 

Investigation	Finding
T3, T4, TSH	T3, T4 – elevated TSH- undetectable (primary), raised (secondary) if abnormal values are found, the tests should be repeated and the abnormality confirmed
TSH receptor antibodies (TRAb)	Graves’ disease
Thyroid scan: Radio-iodine uptake tests / Thyroid scintigraphy	Thyroid scintigraphy: advantages quicker to perform  lower dose of radioactivity, higher-resolution image
ALT, GGT, ALP, Bilirubin	raised
S. calcium	raised
Blood glucose, urinary glucose	glycosuria, DM, IGT
ECG	sinus tachycardia or atrial fibrillation

 

Factitious thyrotoxicosis: (OSPE/SAQ)

• Consumption of excessive amounts of a thyroid hormone preparation (levothyroxine) 
• The exogenous levothyroxine suppresses pituitary TSH secretion and hence suppresses 
  • iodine uptake, serum thyroglobulin and release of endogenous thyroid hormones. 
• The T4 :T3 ratio (typically 30:1 in conventional thyrotoxicosis) is increased to above 70:1
• Lab finding: 

1. T3 – normal, T4 – raised, TSH- low/undetectable; high T4 :T3 ratio 
2. Low iodine uptake
3. Low or undetectable thyroglobulin.

 

Management of thyrotoxicosis:

• Definitive treatment of thyrotoxicosis depends on the underlying cause 
• Mode of treatment: 
  • antithyroid drugs, 
  • radioactive iodine 
  • surgery. 
• β-blocker: propranolol (160 mg daily), will alleviate but not abolish symptoms in most patients within 24–48 hours. Alternative: Verapamil. 

 

Atrial fibrillation in thyrotoxicosis

 

• The incidence is higher in men and increases with age (60 years) 
• Rate control: digoxin plus β-blocker. 
• Anticoagulation 
• Cardioversion may be required in some cases

 

Thyrotoxic crisis or thyroid storm

 

Signs:

• fever, agitation, delirium, 
• tachycardia or atrial fibrillation, cardiac failure. 
• Harrison: fever, delirium, seizures, coma, vomiting, diarrhea, jaundice

 

Precipitation:

1. acute illness: (e.g., stroke, infection, trauma, diabetic ketoacidosis) in a patient with previously unrecognized or inadequately treated thyrotoxicosis. 
2. Surgery: in known thyrotoxicosis, shortly after thyroidectomy in an ill-prepared patient 
3. Radioiodine therapy: within a few days of 131I therapy.

 

Mortality: 10%

• Cardiac failure, arrhythmia, or hyperthermia

 

1. Take 4 history?

• Fever
• History of 
  • treatment with antithyroid drug
  • recent radioiodine therapy
  • recent thyroid surgery

 

1. List 4 important clinical sign

• Signs of dehydration: sunken eyes, dry mucosa, dry skin
• GCS
• Basal crepitation / respiratory rate
• Enlarged thyroid gland / surgical scar
• Exophthalmos

 

1. Write 5 principles of management

• • IV fluid / correction of dehydration 
  • Beta blocker 
  • Sodium ipodate 
  • IV steroid/dexamethasone 
  • Antithyroid/ carbimazole 
  • Antibiotics 

• Antipyretic 

Management:

 This is a medical emergency, requiring intensive monitoring and supportive care

• • Referral: Urgent specialist endocrine input 

• First 3 steps: (for easy remembering)

1. Rehydration with IV fluid
2. Oxygen
3. Cooling

 

• 2 ancillary steps:

1. Propranolol: orally (80 mg 4 times daily) or intravenously (1–5 mg 4 times daily). 

• anti adrenergic effect : caution → acute negative inotropic effects

1. Hydrocortisone: 100 mg IV every 8 hours: block conversion of T4 to T3

• 2 main steps 

• Oral propylthiouracil (PTU) 

• loading dose: 500–1000 mg, then 200 mg every 4 hours (oral, NG tube, rectal)
• inhibit synthesis and conversion of T4 to T3
• if not available, carbimazole (20 mg every 6 hours) 

• Iodine: Sodium ipodate/ potassium iodide or Lugol’s solution

• One hour after the first dose of propylthiouracil, 

• block hormone synthesis via the Wolff-Chaikoff effect

• Rest 2 steps:

1. Antibiotics: if infection is suspected
2. Cholestyramine: to sequester thyroid hormones

 

Monitoring: cardiac monitoring, haemodynamic status

 

Follow up: After 10–14 days the patient can usually be maintained on carbimazole alone.