Endocrine System: Thyroid Disorders

Hyperthyroidism hormone characteristics

• High T3 and T4

• Low TSH

• Increased metabolism and activity

Signs and symptoms of hyperthyroidism

• Hyperactivity

• Anxiety and irritation

• Insomnia and tiredness

• Heat sensitivity

• Weight loss

• Diarrhoea

• Polyuria

• Palpitations

• Goitre

Hyperthyroidism treatment

• First line: carbimazole

• Prophylthiouracil

MHRA warnings for carbimazole

• Congenital malformations → strengthened contraceptive advice

• Acute pancreatitis → immediately and permanently stop

• Bone marrow suppression → report and stop immediately

When is prophylthiouracil contraindicated?

• Liver disorder → jaundice, dark urine, nausea

Which medicines can provide symptomatic relief in hyperthyroidism?

Beta blockers

Treatment for Grave’s disease

First line: Radioactive iodine

• If remission is likely to be achieved with anti-thyroids, can consider carbimazole

• Use carbimazole if iodine and surgery are unsuitable

  • Given as a block and replace regimen in combination with levothyroxine for 12-18 months

Grave’s disease treatment in pregnancy

• Use prophylthiouracil if trying to become pregnant in the next six months

• After radioactive iodine treatment, avoid pregnancy for 6 months (men avoid for 4 months)

Hypothyroidism hormone characteristics

• Low T3 + T4

• High TSH

• Decreased metabolism and activity

Signs and symptoms of hypothyroidism

• Tiredness

• Weight gain

• Depression

• Constipation

• Intolerance to cold

• Dry skin

• Menstrual irregularities

Hypothyroidism treatment

First-line: levothyroxine

• Monitor TSH every 3 months until stable, then yearly thereafter

• Take in the morning at least 30 mins before having breakfast/caffeinated drinks

• MHRA: new guidance that a small proportion of patients may feel symptoms if alternating between brands

Liothyronine

• Do not routinely offer liothyronine either alone or in combination with levothyroxine

Levothyroxine interactions

• Antacids, calcium, aluminium, and magnesium - reduce absorption of levothyroxine (leave 4-hour gap)

• Affected by CYP450 enzyme inhibitors and inducers

• Levothyroxine may cause hyperglycemia, reducing effects of antidiabetic treatment

• Ferrous sulfate reduces absorption of levothyroxine - 2-hour gap

• Orlistat may decrease levothyroxine absorption