Define it
Condition in which the thyroid gland is underactive, resulting in deficiency of the thyroid hormones T3 & T4
Define subclinical hypothyroidism
May occur in intercurrent illness → high TSH with normal T3 and T4
How do we treat it in patients <65 years with hypothyroidism symptoms?
Trial of levothyroxine
How do we treat it in patients >65 years or asymptomatic?
Observe and repeat TFTs in 6 months
When would we treat asymptomatic patients?
If TSH level >10 mU/L on 2 separate occasions 3 months apart
What are the 2 types of causes?
- Congenital - such as
- Thyroid dysplasia
- Thyroid aplasia
- Acquired - such as
- Hashimoto’s thyroiditis (autoimmune)
- Postpartum thyroiditis
- De Quervain thyroiditis
- Iatrogenic (post-surgery)
- Lithium toxicity
What causes secondary hypothyroidism?
Pituitary disorders (e.g. pituitary adenoma) leading to TSH deficiency
What group does it happen more in?
F>M
What’s the most common cause of it worldwide?
Iodine deficiency
In developed countries where iodine consumption is normal- most common is Hashimoto’s thyroiditis
What more serious condition is Hashimoto’s linked with?
MALT lymphoma (non-Hodgkin lymphoma) A cancer of B lymphocytes that arises in tissues associated with mucous membranes
Hashimoto’s thyroiditis- an autoimmune disease that affects the thyroid gland.
Clinical features
Decreased basal metabolic rate :
- Slow cognition
- Apathy
- Dry skin
- Cold intolerance
Decreased sympathetic activity:
- Decreased sweating
- Constipation
- Bradycardia
- Fatigue
- Hair loss
- Weight gain (despite poor appetite)
- Depression
- Menorrhagia (heavy periods)
What is a feature you’d see in Hashimoto’s on examination?
Firm and non-tender goitre
What is the main investigation we do?
TFTs
- Primary → increased TSH, decreased T4 & T3
- Secondary → decreased TSH, decreased T4 & T3
What may we see in a normal pregnancy for TFTs?
Normal TSH, fT4 and fT3 but raised total T3 and total T4
This is because of high conc of thyroid-binding globulins
If we suspect pituitary insufficiency what do we do?
MRI
What other investigation do we do?
Antibody testing for autoimmune hypothyroidism
For Hashimoto’s we would see Anti-TPO
What electrolyte may be affected?
Can get euvolaemic hyponatraemia
What do you see in sick euthyroid syndrome?
Sick euthyroid syndrome- Your thyroid gland itself is normal, but your thyroid blood tests look abnormal because of another illness or stress on the body.
low T3/T4 and normal TSH with acute illness
What is 1st line?
Lifelong levothyroxine, adjust dose based on TFTs. Need to check TSH annually
What would we see in poor compliance with levothyroxine?
Raised TSH and normal T4
How is the dose of levothyroxine affected in pregnancy?
Should be increased by up to 50% as early as 4-6 weeks of pregnancy
How do we advise patients taking levothyroxine who are also taking iron/calcium supplements?
Take iron/calcium 4 hours apart from levothyroxine as they can reduce levothyroxine absorption
What do we do in patients with amiodarone-induced hypothyroidism?
Amiodarone is very iodine-rich and directly affects how thyroid hormones are made and processed—so it can push the thyroid out of balance
Give levothyroxine and can continue amiodarone
What is myxoedema coma?
severe hypothyroidism causing impaired mental status, hypothermia, hypotension
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Diabetics Mellitus58
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Addison's disease23
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Phaeochromocytoma5
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Cushing’s Syndrome18
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Obesity15
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Diabetic Eye Disease16
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Hypoglycaemia15
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Hyperosmolar hyperglycaemic state15
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Diabetic neuropathy19
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Hypothyroidism26
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Hyperparathyroidism15
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Primary Hyperaldosteronism8
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Diabetes ketoacidosis18
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Hyperlipidaemia15
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Hyperthermia and hypothermia21
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Thyrotoxicosis20
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Diabetes inspidus17
