Pituitary Disorders

Pathophysiology and implications of various pituitary disorders

  • Posterior lobe is responsible for the secretion of oxytocin & ADH
  • Anterior lobe is responsible for secreting:  Growth hormone, ACTH, TSH, prolactin, FSH, LG
  • Growth hormone has anti-insulin effects on lipid & carb metabolism, increases muscle mass & stimulates the formation of insulin-like growth factors
    • Excessive growth hormone:  acromegaly (aka gigantism)
      • Slow development of soft tissue overgrowth of many body symptoms resulting in the coarsening of facial features, increased hand & foot size, dermatological conditions
      • Clinical sequelae:  CVD, OA, sleep apnea, type 2 diabetes mellitus
    • Growth hormone deficiencies can result in short stature
  • Hyperprolactinemia may be caused by either pituitary tumors, microadenomas, or medication induced (meds that antagonize dopamine & increase serotonin)
    • Presentation:  headaches, visual disturbances
    • Men:  decreased libido, ED, gynecomastia
    • Women:  menstrual irregularities
    • Sequele inhibit gonadotropin secretion & sex-steroid synthesis
  • Panhypopituitarism is complete or partial loss of the anterior & posterior pituitary function resulting in multiple pituitary hormone deficiencies
    • Cause of primary panhypopituitarism:  abnormality within secretory cells of pituitary
    • Causes of secondary panhypopituitarism:   lack of proper external stimulation needed for appropriate pituitary hormone release

Therapeutic options & monitoring for treating pituitary disorders

  • Treatment of acromegaly (excessive growth hormone)
    • Dopamine agonist (bromocriptine, cabergolide, pergolide) cause a paradoxical decrease in GH
      • Inexpensive, convenient oral admin
      • SE:  CNS symptoms, GI effects
    • Octreotide (injectable):  more potent inhibitor of GH secretion
      • SE:  GI effects are common
    • Pegvisomat (injectable):  GH receptor antagonist
      • SE:  GI effects are common, hepatotoxicity
    • May due combo therapy
  • Growth hormone deficiency (GHD)
    • 3 criteria for definitive diagnosis:  subnormal growth velocity, delayed bone age, subnormal GH response to at least two proactive stimuli (insulin induced hypoglycemia, clonidine, L-dopa, arginine, glucagon, GHRH)
    • Treatment:  recombinant growth hormone formulations (genotropin, hymatrope, norditropin, etc)
      • All are equally effective & administered subcutaneously
      • SE:  decreased insulin sensitivity, neoplasm, joint pain, retinopathy
    • Other treatment options:  recombinant IGF-1, GHRH
  • Hyperprolactinemia
    • Treatment:  depends on the underlying cause but usually dopamine agonists (bromocriptine, pergolide, cabergoline) are used
      • If it is drug induced hyperprolactinemia, remove the agent
        • Drugs that can induce hyperprolactinemia:  dopamine antagonists (antipsych, phenothiazines, metoclopramide, etc), prolactin stimulators (antidepressants, estrogens, protease inhibitors, opioids, benzos, H2RAs, etc), verapamil
  • panhypopituitarism
    • Replacement of specific pituitary hormones:  glucocorticoids, thyroid hormone, sex steroids, growth hormone
    • Life long replacement is needed
Hormone Deficit

Hormone Replacement

ACTH

Hydrocortisone 10-20 mg QAM and 5-10 mg QPM

Cortisone 25 mg QAM and 12.5 mg QPM

Prednisone 5 mg QAM and 2.5 mg QPM

FSH/LH

Males: testosterone 200 mg IM q week or 5 mg topically daily

Females: Conjugated Estrogens 0.625 mg PO QD for 25 days & progesterone 5-10 mg PO QD on days 16-25.

For fertility purposes in women use hCG

GH

Children: Somatotropin 0.02-0.05 mg/kg/day

Adults: Somatotropin 0.1-1.25 mg SC every other day

TSH

Levothyroxine (Synthroid) 75-150 mcg/day

Vasopressin

Intranasal Desmopressin 5-20 micrograms BID or 300-600 micrograms QD

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