Endocrinology - Thyroid

Question 1

Differentiate between primary and secondary hypothyroidism

Answer 1

Primary
- thyroid gland not making enough thyroid hormone
- high TSH low T3/T4
- autoimmune hypothyroidism from Hashimoto’s
- iodine induced
- drug induced (amiodarone)
Secondary
- central where failure of pituitary stimulation of thyroid hormone
- low TSH and T3/T4
- pituitary disease (tumour)

Question 2

Discuss the presentation, investigations to hypothyroidism

Answer 2

Presentation
- weight gain
- dry/itchy/cold/coarse skin
- hair loss
- fatigue
- cold intolerance
- depression, psychosis
- joint pain and muscle cramps   
      - muscle weakness
- constiptation
- menstrual irregularities and menorrhagia
- myxedema (non pitting edema)
- puffiness with coarse brittle hair (eyebrow)
- peri-orbucular swelling
- enlarged tongue
- goitre
- delayed deep tendon reflex
- carpal tunnel syndrome
- bradycardia and diastolic hypertension
Investigation
- TSH and Free T3/T4
      - subclinical T4 may be normal

Question 3

Discuss the management for hypothryoidism

Answer 3

Levothyroxine
- synthetic T4 (body can convert to T3)
- start at 1.7mcg/kg/d
      - monitor response at 6 weeks
      - primary target to TSH <5    
      - in pregnancy may require more and target is <2
Indications
- TSH >10
- Symptomatic
- Subclinical and pregnancy
- hypertension, hypercholesterolemia

Question 4

Differentiate between primary and secondary hyperthyroidism

Answer 4

Primary
- thyroid gland overproduce thyroid hormone despite good negative feedback loop
      - TSH low and Free T3/T4 high
- autoimmune: Grave's
- toxic nodular goitre
- hyperthyroid phase of acute thyroidits
- excessive synthroid, amiodarone, iodine in diet
Secondary
- pituitary excrete excessive TSH
      - high TSH and T3/T4
- pituitary adenoma

Question 5

Discuss the presentation and investigations for hyperthyroidism

Answer 5

Presentation
- heat intolerance, sweating, weight loss
- anxiety, insomnia
- palpitation
- muscle aches, hyperactivity
- frequent bowel movements
- loss of libido
- moist skin
- tremor
- diffuse goitre and bruit
- tachycardia and systolic hypertension
- palmar erythema, onycholysis
- lid lag, proptosis
- hyperreflexia
- pretibial myxedema
Investigation
- TSH, T3/T4
- Radioactive Iodine Uptake

Question 6

Discuss the findings of TSH, T3/T4, radioactive uptake and thyroglobulin for different causes of hyperthyroidism

Answer 6

Graves
- low TSH
- very High T3/T4
- very High Radioactive uptake
Toxic Nodule
- low TSH
- high T3/T4
- high radioactive uptake
Subacute thyroiditis
- low TSH
- high T3/T4
- low radioactive iodine uptake
- high thyroglobulin
Factitious Thyrotoxicosis
- low TSH
- high T3/T4
- low radioactive iodine uptake
- low thyroglobulin
TSH Secreting tumour
- high TSH
- high T3/T3
- high radioactive iodine uptake

Question 7

Discuss the management of hyperthyroidism

Answer 7

Antithyroid Drugs
- Methimazole and Propylthiouracil
- inhibit thyroperoxidase
- PTU also inhibit deiodinase that convert T4 to T3
- PTU used in first 16weeks of pregnancy and then methimazole
- MMI increased risk of aplasia cutis
- PTU increased risk of hepatotoxicity in second and third trimester
- MMI normally preferred due to rapid onset and once daily dosing
Radioactive Iodine
- cure Grave disease, multi nodular goitre or toxic nodule
- can not use in women if wanting to get pregnant in next 6 months
Subtotal surgical Thyroidectomy
- last line
Beta Blocker
- symptomatic
- propanolol

Question 8

Discuss the pathophysiology, presentation, and management of subacute thyroiditis

Answer 8

• inflammatory disorder of the thyroid
• Painful: De Quervain’s (viral, granulomatous)
• Painless; Silent (post-partum, auto-immune)
  Pathophysiology
• acute inflammation with giant cells and lymphocytes disrupts the thyroid cells causing release of stored thyroid hormone
  Presentation
• pain in thyroid, ears, jaw
• post-partum: 2-3 month and then hypothyroid 4-8 month
  Management
• Painful: high dose NSAID, prednisone
• BB

Question 9

Discuss the pathophysiology, presentation, investigation, and management for thyroid storm

Answer 9

Pathophysiology
- infection
- trauma
- surgery
Presentation
- Hyperthyroidism
- Hyperthermia >40
- Vascular collapse with tachy
- Vomiting
- Hepatic failure with jaundice and confusion
Investigations
- Increase T3/T4
- Hyperglycemia, hypercalcemia
Management
- Fluids, electrolytes, vasopressors
- cooling blanket
- BB
- PTU treatment of choice
- Iodide 1hr after PTU
- Dexamethasone

Question 10

Discuss the pathophysiology, presentation and management of myxedema coma

Answer 10

Pathophysiology
- Severe hypothyroidism from trauma, sepsis, cold exposure, MI
Presentation
- decreased mental status and hypothermia
- hyponatremia, hypotension, hypoglycemia, hypoventilation
Investigations
- Decreased T4, increased TSH
- ACTH and cortisol check
Management
- Corticosteroids
- L-thyroxine 0.2-0.5mg IV
- Supportive measures