Acquired Hypothyroidism

Question 1

Is acquired hypothyroidism common?

Answer 1

Relatively

Question 2

What is acquired hypothyroidism?

Answer 2

A condition where the thyroid gland makes insufficient thyroid hormone

Question 3

What is primary hypothyroidism due to?

Answer 3

Inadequate function of the gland itself

Question 4

What is secondary hypothyroidism due to?

Answer 4

A problem upstream of the thyroid gland

Question 5

What problems upstream of the thyroid gland can cause secondary hypothyroidism?

Answer 5

• Inadequate stimulation by TSH from the pituitary gland

- Inadequate release of thyrotropin-releasing hormone from the brain’s hypothalamus

Question 6

How much more common is primary hypothyroidism than secondary hypothyroidism?

Answer 6

1000x

Question 7

What are the causes of primary hypothyroidism?

Answer 7

• Autoimmune
• Iodine deficiency
• Subacute thyroiditis
• Drugs
• Post-irradiation
• Post-ablative

Question 8

What are the autoimmune causes of primary hypothyroidism?

Answer 8

• Hashimoto’s

- Chronic lymphocytic thyroiditis

Question 9

Give two examples of drugs that can cause hypothyroidism

Answer 9

• Amiodarone

- Lithium

Question 10

Give two causes of ablative hypothyroidism

Answer 10

• Radioiodine therapy

- Surgery

Question 11

What will be found on blood tests in central hypothyroidism?

Answer 11

• Low serum TSH

- Low T4

Question 12

What are the causes of central hypothyroidism?

Answer 12

• Intracranial tumour/mass
• Post cranial radiotherapy/surgery
• Developmental pituitary defects

Question 13

What is the problem with the diagnosis of acquired hypothyroidism?

Answer 13

The symptoms and signs and usually insidious, and can be extremely difficult to diagnose clinically

Question 14

What is the result of the signs and symptoms of acquired hypothyroidism usually appearing insidiously?

Answer 14

A high index of suspicion is required

Question 15

What are the symptoms of acquired hypothyroidism?

Answer 15

• Dry skin
• Constipation
• Delayed puberty/amennorhoea
• Poor concentration and deterioration in school work

Question 16

What are the signs of acquired hypothyroidism?

Answer 16

• Cold intolerance
• Thin, dry hair
• Bradycardia
• Cold peripheries
• Goitre
• Slow-relaxing reflexes
• Slipped upper femoral epiphysis
• Short stature/poor growth

Question 17

What investigations should be done in acquired hypothyroidism?

Answer 17

• Thyroid function tests

- Thyroid antibody screen

Question 18

What might the thyroid antibody screen show in acquired hypothyroidism?

Answer 18

Raised antibody titres for;

• Anti-thyroid peroxidase
• Anti-thyroglobulin
• TSH receptor (blocking type)

Question 19

What are the differential diagnoses for acquired hypothyroidism?

Answer 19

• Other causes of short stature
• Other causes of fall-off in growth
• Other causes of goitre

Question 20

How is acquired hypothyroidism managed?

Answer 20

Oral levothyroxine 25-200micrograms/day

Question 21

What monitoring is required in acquired hypothyroidism?

Answer 21

Need to monitor TFTs every 4-6 months during childhood, and monitor growth and neurodevelopment

Question 22

What are the complications of acquired hypothyroidism?

Answer 22

Increased risk of developing other autoimmune disorders, e.g. vitiligo, RA