Lec 2 Hypopituitary Flashcards
Where are posterior pituitary hormones made?
made in hypothalamus; stored in pituitary
Is hypopituitarism vs end organ hormone deficiency more severe?
end organ deficiency is more severe –> in absence of pituitary trophic hormones end organs will still continue to secrete some hormone
What are 3 causes of hypopituitarism?
- primary pituitary disorder = loss of hormone secreting cells
- hypothalamic disorder = loss of releasing hormones
- extrinsic destruction of hypothalamus/stalk/pituitary gland
What is embryology of anterior pituitary?
derived from rathkes pouch = ectodermal pouch of primordial oral cavity
What is embryology of posterior pituitary?
direct extension of nervous system
What is a cranyopharyngioma?
tumor derived from remnants of rathkes pouch
What is the one exception to the rule that all of the hormones secreted from hypothalamus are peptides?
dopamine = modified tyrosine molec
Which part of pituitary connects to hypothalamus via capillary portal system?
anterior pituitary
What two hormones are secreted by posterior pituitary?
- ADH/vasopressin
- oxytocin
What are x etiologies of hypopituitarism?
- invasion [tumor/cystic lesion]
- iatrogenic [surgery/radiation]
- infiltration [sarcoid, hemochromatosis]
- infarction [postpartum sheehans]
- injury [head trauma]
- infection [TB, syphilis]
- immune [autoimmune
What type of cell secretes growth hormone?
somatotroph
What type of cell secretes TSH?
thyrotroph
What type of cell secretes LH/FSH?
gonadotroph
What type of cell secretes ACTH?
corticotroph
What type of cell secretes prolactin?
lactotroph
What is action/target organs of growth hormone?
stimulates linear growth and muscle mass by causing secretion of IGF1[somatomedin]
anti-insulin effects
What are 4 actions of T3/T4?
- thermogenesis = increase BMR via Na/K ATPase
- increase B1 receptors in heart –> increase CO/HR/SV
- bone growth
- CNS maturation
What is action of ADH?
regulates serum osmolarity and BP –> decreases serum osmolarity and increases urine osmolarity via aquaporins in kidney
What is action of prolactin?
stimulates milk production
inhibits ovulation and females and spermatogenesis in males by inhibiting GnRH synthesis and release
Where is anterior pituitary located?
sella turcica
What is action of LH?
stimulates sex steroid hormone synthesis in gonads
What is action of FSH?
follicular development in females; spermatogenesis in males
What is regulation of prolactin?
under tonic inhibition from dopamine –> only secrete prolactin when really low dopamine
high TRH can also stimulate prolactin
What 2 things stimulate prolactin secretion?
- suckling
- high estrogen
What is structure of FSH/LH/TSH/HCG?
glycoprotein hormones with alpha and beta subunits
same alpha; different beta
What is order of loss of pituitary hormones [ACTH, FSH, GH, LH, TCH]?
first: GH –> FSH/LH –> TSH –> ACTH
What condition can present with isolated ACTH deficiency?
hypophysitis
What is effect of loss of posterior pituitary hormones?
diabetes insipidus
What is pituitary apoplexy? presentation?
sudden hemorrhage into pituitary –> severe headache, double vision, acute onset hypopituitarism; sudden onset ACTH deficiency –> severe hypotension
can be due to pituitary adenoma
What is major cause of hypopituitarism in adults?
pituitary tumor or treatment of pituitary tumor
What is sheehan’s syndrome? early sign?
pituitary infarction from massive blood loss during childbirth
early sign = inability to lactate after childbirth
What are 3 mass-effect symptoms of pituitary sella tumors?
headahce, bitemporal heminopia, galactorrhea
What are symptoms of pan-pituitary hormone deficiency?
- amenorrhea or erectile dysfunction
- wrinkling of skin
- loss of axillary and pubic hair
- low BP from low cortisol
- loss of lateral eyebrows
- sallow complexion
- more fat / less muscle
How does pediatric hypopituitarism present?
- abnormal growth / falling off growth curve
- can also see isolated deficiencies from congenital releasing hormone deficiencies
What do you see in pediatric GH deficiency?
unexplained short stature
What are x causes of pediatric GH deficiency?
- isolated GHRH deficiency
- pituitary tumor
- GH insensitivity [laron dwarf]
What lab levels do you see in laron dwarf?
high GH but not IGF1 = absent GH receptor
How do you test for pediatric GH deficiency?
give GHRH and measure GH response
What do you see in pediatric gonadotropin deficiency?
abnormal 2ndary sex characteristics [microphallus] or failure to sexually mature at expected time
have long arms and legs b/c low sex steroids which are responsible for puberty growth spurt
What are two causes of pediatric gonadotropin deficiency?
- kallmann syndrome = GnHr deficiency
- tumor damaging gonadotrophs
What disease is characterized by anosmia + failure to sexually mature at expected time?
kallman syndrome
What do you see in craniopharyngioma?
tumor causes delay or absence of pubertal development
seen in kids
have short stature and severe hypogonadism
tumor = has lots of calcification b/csimilar origin to teeth
What is another name for posterior pituitary?
neurohypophysis
What is action of oxytocin?
release of milk from breast
uterine contraction at childbirth
What are two causes of diabetes insipidus?
- deficiency in ADH secretion from PP
- resistance to ADH at level of kidney
What are symptoms of diabetes insipidus?
- polyuria [> 3 L/day]
- inability to concentrate urine despite increase in plasma osmolality
What must be ruled out when you think diabetes insipidus?
psychogenic polydipsia
What are causes of central diabetes insipidus?
due to ADH deficiency
- pituitary stalk transection
- post-pituitary surgery
- autoimmune
- malignancy
- familial
What are causes of nephrogenic diabetes insipidus?
vasopressin resistance
- hereditary [ADH receptor gene mutation]
- lithium tox
- hyper-CA
- hypo-K
How do you distinguish central DI vs nephrogenic DI vs psychogenic polydyspia
central: on water deprivation, can’t concentrate urine; if administer exogenous ADH [desmopressin] –> improves
nephrogenic: on water deprivation, can’t concentrate urine; no change with exogenous ADH
psychogenic: on water deprivation, urine becomes concentrated + decrease quantity
What is microadenoma vs macroadenoma of pituitary?
microadenoma < 1 cm
macroadenoma > 1 cm
What hormone should be replaced first in hypopituitarism?
replace cortisol first
What are 4 things that inhibit ADH?
- adequate water
- ethanol
- a-adrenergic agonists
- ANP
What water/Na state cause release of ADH?
- increase serum Na/osmolarity
- low BP/hypovolemia/hemorrhage
