Endocrinology - Hypothyroidism Flashcards

1
Q

Causes of hypothyroidism

A

Hashimoto’s thyroiditis

Iodine deficiency (rare in UK)

Secondary to treatment of hyperthyroidism

Medications e.g. lithium and amiodarone

Secondary hypothyroidism - hypopituitarism

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2
Q

Hashimoto’s thyroiditis cause

A

Autoimmune inflammation of thyroid gland

Associated with antithyroid peroxidase (anti-TPO) antibodies and antithyroglobulin antibodies

Most common cause in the UK

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3
Q

Iodine deficiency as a cause

A

Most common cause of hypothyroidism in developing countries

Rare in UK as iodine added to foods such as salt to prevent this

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4
Q

What medications/procedures can cause hypothyroidism?

A

Those used to treat hyperthyroidism:

  • Carbimazole and PTU
  • Radioactive iodine
  • Thyroid surgery

Lithium - inhibits the production of thyroid hormones in the thyroid gland (can cause goitre and hypothyroidism)

Amiodarone - interferes with thyroid hormone production and metabolism (usually causes hypo but can also cause hyperthyroid)

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5
Q

Causes of secondary hypothyroidism

A

Tumours
Infection
Vascular (e.g. Sheehan Syndrome)
Radiation

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6
Q

Presentation of hypothyroidism

A
Weight gain
Fatigue
Dry skin
Coarse hair and hair loss
Fluid retention (oedema, pleural effusions, ascites)
Heavy or irregular periods
Constipation
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7
Q

Investigations in hypothyroid

A

TFTs - TSH and T3/4

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8
Q

High TSH and low T3/4

A

Primary hypothyroidism - most likely Hashimoto’s thyroiditis

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9
Q

Low TSH and low T3/4

A

Secondary hypothyroidism (hypopituitarism)

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10
Q

Management of hypothyroidism

A

Levothyroxine (synthetic T4 - which metabolises to T3 in the body)

Dose is titrated until TSH levels are normal

Initially TSH measured monthly but less frequently once stable.

  • If TSH is high - need to increase dose
  • If TSH low - need to reduce dose

Initially 1.6 micrograms/kg once daily to nearest 25 micrograms

Dose taken before breakfast

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