(incomplete) Hyperthyroidism, Thyrotoxicosis and Thyroid Storm

Question 1

Thyrotoxicosis is the general term for the presence of increased __, __ or both due to any cause.

Subclinical hyperthyroidism is __ and __
Clinical signs and symptoms are __ or __

Answer 1

Thyrotoxicosis
Increased T4 - thyroxine
Increased T3 - tri-iodothyronine

Subclinical hyperthyroidism
Low TSH
High-normal T4 or T3
Absent or non-specific

Question 2

Natural progression of subclinical hyperthyroidism

Answer 2

1. Progression to clinical thyrotoxicosis
2. Reduced bone mineral density, accelerated bone loss, fracture risk
3. Atrial fibrillation, impaired LV diastolic filling, impaired LVEF
4. Overall increase in mortality

TSH < 0.1 mU/L more likely associated with adverse consequences

Question 3

Does subclinical hyperthyroidism requires teratment?

Answer 3

Treatment Criteria:
1. TSH < 0.1 mU/L
2. Age 65 years and older, or
3. Younger but with symptomatic disease or comorbidities that may aggravate hyperthyroidism (CVS, OP, menopause)

(Consider treatment if TSH 0.1-0.4 mU/L too)

Question 4

Graves’ disease is an __ disease in which __ are directed against __
- Results in continuous stimulation of __ and __ (goitre)
- There is extrathyroidal manifestations such as (3)

Answer 4

Autoimmune disease - autoantibodies directed against TSH receptor (TSHRAb)
- Stimulation of thyroid hormone production and secretion, thyroid growth (goitre)

Extrathyroidal manifestations
1. Orbitopathy - proptosis, periorbital oedema, EOM dysfunction, optic neuropathy
2. Dermopathy - pretibial myxedema
3. Thyroid acropachy - digital clubbing/oedema

Question 5

Jod-Basedow phenomenon

Answer 5

Exposure to large quantities of iodine causes thyrotoxicosis
- Iodine supplementation in iodine deficiency
- Iodinated radiographic contraast
- Amiodarone

Question 6

Symptoms of hyperthyroidism

Answer 6

Palpitations
Anxiety
Restlessness
Insomnia
Impaired concentration/memory
Irritability
Emotional liability
Weight loss
Heat intolerance
Sweating
Exertional dyspnoea
Fatigue
Hyperdefecation
Amenorrhoea / oligomenorrhoea
Anovulation
Hair thinning
Polyphagia and resultant weight gain

Question 7

Signs of thyrotoxicosis

Answer 7

Tremors
Tachycardia
Flow murmur
Hypertension
Warm and moist skin
Thin and fine hair
Hyperreflexia with rapid relaxation pahase
Lid lag/retraction
Goitre
Orbitopathy
Pretibial myxedema
Acropachy
Thyroid bruit

Question 8

Pathogenesis of thyroid eye disease

Answer 8

1. Sympathetic/adrenergic overactivity - lid retraction and stare
2. Thyroid autoantibodies cross-react with antigens in fibroblasts, preadipocytes and adipocytes of retroorbital tissues
3. Insulin-like growth factor-1 receptor signal transduction

Question 9

Laboratory confirmation of hyperthyroidism

Answer 9

1. TSH - suppressed / low
2. fT4 and fT3 - elevated

Answer 10

FBC - leukopenia, NCNC anaemia
LFT - hepatic transamnitis, ALP, low albumin
BMP - hypercalcaemia, hyperphosphataemia

Question 12

Management of Thyroid Storm

Answer 12

A. Thyroid hormone production inhibition
1. Propylthiouracil - 600mg loading, then 200-250mg Q4-6H
(Contraindicated in agranulocytosis, liver dysfunction)
2. Carbimazole - 20mg Q4H

B. Beta adrenergic antagonist
1. Propranolol 40-80mg Q4-6H (IV 1-2mg)
2. Esmolol 50-100mcg/kg/min

C. Thyroid hormone release inhibition
1. Sodium iodide 1g BD (dilute in 500mL NS infuse over 4-6 hours)
- Given 1 hour after anti thyroid drugs
2. Lugol’s idodine 10 drops TDS (65mg)

D. Supportive
1. IV Hydrocortisone 100mg Q8H or
2. IV Dexamethasone 2mg Q6H
- inhibits T4 to T3 conversion
- Also covers concomitant adrenal insufficiency