Hypothyroidism Flashcards
Causes
Hashimoto’s thyroiditis
Iodine deficiency
Secondary to treatment of hyperthyroidism
Medications (lithium and amiodarone)
Central causes (secondary)
Hashimoto’s thyroiditis
Most common cause of hypothyroidism in developed world
Caused by autoimmune inflammation of the thyroid
Associated with antithyroid peroxidase antibodies and antithyroglobulin antibodies
Initially causes goitre then atrophy of thyroid gland
Iodine deficiency
Most common cause in developing world
Iodine added to foods such as table salt
Treatment for hyperthyroidism causing hypothyroidism
Carbimazole
Propylthiouracil
Radioactive iodine
Thyroid surgery
Secondary causes of hypothyroidism
Pituitary gland is failing to produce enough TSH
Tumours
Infection
Vascular (e.g. Sheehan)
Radiation
Presentation
Weight gain
Fatigue
Dry skin
Coarse hair and hair loss
Fluid retention (oedema, pleural effusions, ascites)
Heavy or irregular periods
Constipation
Decreased deep tendon reflexes
Carpal tunnel syndrome
Results in primary hypothyroidism
Caused by thyroid gland insufficiency
Low T3 and T4
High TSH as no negative feedback
Results in secondary hypothyroidism
Caused by pituitary pathology
Low TSH so low T4 and T4
Management
Oral levothyroxine (synthetic T4 that metabolises to T3 in the body)
Dose titrated until TSH levels are normal
Initially measure TSH levels monthly until stable then monitor less regularly
Other conditions associated with hypothyroidism
Down’s syndrome
Turner’s syndrome
Coeliac disease
Side effects of thyroxine therapy
Hyperthyroidism
Reduced bone mineral density
Worsening of angina
AF
Thyroxine interactions
Iron, calcium carbonate
Absorption of levothyroxine reduced so give at least 4 hours apart
