07. Thyroid Pharmacology

• tests of thyroid function - serum TSH, free T4 and T3 - if TSH is normally its unlikely that there is thyroid disease
• hyperthyroidism:

  • decrease serum TSH
  • increased serum free T3
• hypothyroidism:

  • increase serum TSH
  • decreased serum free T3
• hyperthyroidism main causes: graves', toxic nodular goitres, thyroiditis

  • tachycardia, shortness of breath, atrial fibrillation
  • weight loss, diarrhoea, increased appetite
  • tremor, myopathy, anxiety
• graves' disease = pathogenic antibodies to TSH receptor on thyroid follicular cells

  • mostly genetic
• neonatal hyperthyroidism can occur when TSH-R antibodies cross the placenta from graves' disease, can cause hyperthyroidism

  • failure to thrive, weight loss
• diagnosing hyperthyroidism:

  • iodine uptake scan
  • isotope imaging
  • TPO antibodies are normally positive
  • TSH receptor antibodies positive in nearly all cases
• hyperthyroidism treatment:

  • antithyroid drugs to block hormone synthesis - thionamides block TPO (carbimazole) - can cause rash and joint paint
  • surgical removal of thyroid
  • radioiodine therapy - can lead to hypothyroidism and cancer
• main causes of hypothyroidism: hashimoto thyroiditis (autoimmune with TPO and Tg antibodies, iodine deficiency

  • bradycardia, heart failure
  • rash
  • weight gain and constipation
  • depression and psychosis
• levothyroxine is a synthetic form of thyroid hormone, restores patients to normal thyroid state after hypothyroidism
• thyroid nodules are common in areas of iodine deficiency, may cause thyroid dysfunction/compression of windpipe

  • need to exclude thyroid cancer (rare)

  excluded via:

  • assessing thyroid function and nodule size
  • thyroid ultrasound differentiates solid vs cystic nodules, cystic almost always benign