43. Clinical biochemistry of the hypothalamus, hypophysis

• Dynamic function test
  • Administer insulin -> measure cortisol, GH
  • Administer GnRH -> measure FSH, LH
  • Administer TRH -> measure TSH
• GH excess
  • Administer oral glucose -> GH still high (usually decreases)
• GH deficiency
  • Low levels of IGF-1
  • Administer GHRH -> GH still low (usually increases)
• Hyperprolactinaemia
  • Serum prolactin
  • Administer dopamine agonist -> prolactin still high (usually decreases)
• Diabetes insipidus
  • Water deprivation -> urine osmolality unchanged (usually increases)
  • Administer desmopressin -> urine osmolality increases (normalizes)