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Definition

Hypothyroidism is a deficiency of the thyroid hormones T3 and T4, slowing metabolism throughout the body.

Causes

• Hashimoto’s thyroiditis, the commonest where iodine is sufficient
• Iodine deficiency worldwide
• After thyroidectomy or radioactive iodine
• Drugs such as lithium and amiodarone

Symptoms

• Fatigue and lethargy, weight gain
• Cold intolerance, constipation
• Dry skin, hair loss, hoarse voice
• Bradycardia, depression, menstrual changes

Tests

High TSH with low free T4 in primary hypothyroidism.

Treatment

• Daily levothyroxine on an empty stomach
• Adjust the dose by TSH after 6–8 weeks
• In the elderly and cardiac patients: start low and go slow

Emergency

Myxoedema coma: hypothermia, slow heart and breathing, confusion. Needs ICU care and IV hormone.

Nursing care

• Teach lifelong therapy and timing
• Watch for overdose signs such as palpitations

Exam point

Calcium and iron reduce levothyroxine absorption, so separate them by 4 hours.