Hypopituitarism Flashcards
prolactin is chronically inhibited by what compound?
dopamine
GH is chronically inhibited by what compound?
somatostatin
what are three etiologies of hypopituitarism?
pituitary disease (80%) hypothalamic disease (13%) idiopathic (7%)
what are the manifestations of pituitary apoplexy (hemorrhage)?
hemorrhage into a pituitary adenoma
sudden onset excrutiating headache
diplopia due to pressure on oculomotor nerve
what are the clinical signs of ACTH deficiency - secondary adrenal insufficiency?
low cortisol with simultaneous low ACTH
does NOT result in hyperpigmentation
how is secondary adrenal insufficiency different than primary?
secondary - no hyperpigmentation
secondary - no aldosterone deficiency
what test is used to diagnose adrenal insufficiency? how does it work?
cortrosyn stimulation test
obtain baseline serum cortisol
administer 250 mcg of ACTH
check serum cortisol 30 minutes after injection
check serum cortisol 60 minutes after injection
levels rising over 18 is normal
what are two tests used to diagnose ACTH deficiency?
metyrapone test (blocks conversion of 11-deoxycortisol to cortisol - results in reduced cortisol / compensatory increase in ACTH)
insulin induced hypoglycemia (should cause ACTH secretion)
what are the treatments for ACTH deficiency?
hydrocortisone
why is mineralocorticoid replacement not necessary in secondary adrenal insufficiency?
mineralocorticoids are mediated by renin-angiotensin system, not ACTH
what levels are measured in the diagnosis of TSH deficiency?
serum thyroxine (T4) TSH
what are the T4 and TSH levels in secondary hypothyroidism?
low T4 with simultaneous low TSH
what is the treatment for TSH deficiency?
levothyroxine
when should T4 be given?
only after adrenal function is determined to be normal / treated
what measurement is useless in secondary hypothyroidism as a guide to adequacy of levothyroxine dosing?
TSH
what is the treatment for LH / FSH deficiency in men NOT seeking fertility?
testosterone replacement
what is the treatment for LH / FSH deficiency in men seeking fertility?
LH / FSH if pituitary disease
GnRH in hypothalamic disease
what is the treatment for LH / FSH deficiency in women?
estrogen-progesterone replacement
ovulation induction in those seeking fertility (LH / FSH if pituitary disease, GnRH in hypothalamic disease)
what is the most common measurement used to assess GH?
IGF-1
what is the relationship of likelihood of deficiencies in panhypopituitarism?
GH > LH / FSH > TSH > ACTH
how are GH levels monitored in GH deficiency?
IGF-1 and patient well being
what is the treatment for GH deficiency?
recombinant human GH preparations
what two factors stimulate ADH release?
increase in plasma osmolality
decrease in plasma volume
where are the ADH receptors?
V1 receptors in vasculature
V2 receptors in renal tubules
what do the V1 receptors do?
vasoconstriction
what do the V2 receptors do?
- synthesis of water channels - aquaporins
- aquaporins get inserted into the luminal surface of the collecting duct membrane
- increased permeability of tubules
- reabsorption of solute free water
what is the pathogenesis of central diabetes insipidus?
deficiency of vasopression due to damage of hypothalamus posterior pituitary region
what are the clinical signs of central diabetes insipidus?
hypotonic polyuria hypernatremia loss of pituitary bright spot on MRI lethargy nausea irratability / drowsiness / confusion muscular rigidity / seizures / coma
what is the primary treatment for vasopressin deficiency?
desmopressin (ddAVP) - synthetic vasopressin analogue
what are the two types of ADH deficiency?
transient
permanent
