Definition (Lancet 2007;369:1461)
• Inadequate pituitary hormone production either 2/2 hypothalamic or pituitary def
• Can involve all pituitary axes (“panhypopituitarism”) or only some
• Ant pit hormones stimulated by hypothalamic hormones, post pit (vasopressin/oxytocin) produced in hypothal travel down neurons to be stored in post pit
Pathophysiology (Lancet 2007;369:1461)
• Pituitary blood supply via branches of internal carotid, forming capillary plexus at median eminence of hypothalamus, which feeds the pituitary via long and short portal veins; pituitary stalk is fed by the middle hypophyseal artery
• Cellular damage can occur from compression 2/2 mass occupying lesion (adenoma) after XRT, vascular insufficiency 2/2 stalk injury w/ subsequent anterior lobe infarction
• Defects in multiple gene products can result in pituitary malformation and malfunction
Etiology (Pediatrics 2007;119:e484; Endocrinol Metab Clin North Am 2008;37:235)
• Consider in any child dx’d w/ GH deficiency, anatomic abnormalities of pituitary or stalk on MRI, Hx of intracranial surgery, tumors, or trauma
• Can develop w/ cranial radiation, septo-optic dysplasia, autoimmune hypophysitis, PROP-1, Pit-1, or other transcription factor def
Clinical Manifestations (Lancet 2007;369:1461; Endocrinol Metab Clin North Am 2008;37:235)
• Pituitary lesions often present initially w/ visual impairment; can be classic bitemporal hemianopsia but more often unilateral
• Can present more acutely w/ dysfxn of vital hormones; adrenal insuff, hypoglycemia 2/2 GH deficiency (common presentation in newborns), diabetes insipidus, hypothyroidism, or as growth failure 2/2 growth hormone deficiency or pubertal delay 2/2 hypogonadism (gonadotropin def)
• Prolactin (Prl) is inhibited by dopaminergic signals from hypothalamus—failure of inhibition, inc prolactin and subsequent galactorrhea, hypogonadism
Diagnosis (Lancet 2007;369:1461; Endocrinol Metab Clin North Am 2008;37:235)
• Initial eval interrogate multi pituitary axes & peripheral responses: TSH, fT4, IGF-1, IGFBP3, FSH, LH, AM cortisol, prolactin serum Na & urine Osm, sex steroids
• MRI focused on pituitary/hypothalamus needed to r/o mass lesion
Rx (Pediatrics 2007;119:e484; Endocrinol Metab Clin North Am 2008;37:235)
• Treat underlying etiology (i.e., surgery for amenable pituitary masses)
• Adequate replacement of deficient pituitary hormones
Complications (Pediatrics 2007;119:e484)
• Correction of hypothyroidism can precipitate adrenal crisis in patients w/ unrecognized adrenal insufficiency (inc need for cortisol and inc clearance)
• Growth hormone could precipitate adrenal insufficiency 2/2 decreased production of cortisol from precursors (or increased metabolism) (rare)