Pituitary/H/R/Onc Flashcards
how does PRL cause hypo hypo
inhibiting hypothalamic gonadotropin-releasing hormone secretion
how to screen for macroPRL
polyethylene glycol precipitation
PRL stimuli
TRH
GHRH
Estradiol
Oxytocin
VIP
Serotonin
inhibitors of PRL
dopamine
Prolactin
○ Inhibits it’s own release
○ Stimulates dopamine - likely to inhibit itself
PRL levels
50-250 ng/mL :Drug induced
<40-60 ng/mL: Venipuncture stress and breast stimulation
25-100 ng/mL: secondary to a non-functioning mass that interrupts the dopamine neurons
100-250 ng/mL: microadenomas (prolactinomas </= 1 cm)
> 500 ng/mL: macroprolactinomas
usually first sign in hyperPRL
hypogonadism
(more than lactation)
first labs to do when PRL high to r/o other
HCG and TFT and GH
tx hyperPRL
dopamine agonist
- bromocryptine
- carbergoline
causes of hyperPRL
- Prolactinoma
- Macroprolactinemia: due to antibodies causing a large prolactin aggregate, which is not active so has no symptoms, but only increases bound prolactin
- Pituitary stalk disruption
○ Non-functioning tumours, craniopharyngiomas, granulomatous infiltration, TBI
○ Decreased dopamine inhibition from hypothalamus - Stress - surgery, exercise, hypoglycemia, acute MI
- Breast disease, nipple stimulation, disease or injury to the chest wall, spinal cord injury, burns, herpes zoster
○ Neurogenic reflex: PRL secretion stimulated by activation of afferent neural pathways - Hypothyroidism
○ Hyperplasia of lactotrophs and thyrotrophs, presumably due to TRH hypersecretion - Dopamine receptor blockers (metoclopramide, antipsychotics): stops dopamine from inhibiting prolactin release
- Renal failure and liver failure
○ Impaired renal degradation of prolactin and altered central prolactin regulation - Estrogen: binds to estrogen receptor (response element) that controls the prolactin gene in the lactotrophs
- Pregnancy/lactation: physiologic increases prolactin
meds causing hyperPRL
rispiridone
olanzapine
size of PRLoma
Macroprolactinoma: >/=1cm
Microprolactinoma: <1cm
syndromes w PRLoma
MEN1’
Familial hyperprolactinemia
Familial isolated pituitary adenoma
most common H w pit adenoma
PRLoma - 66%
indications to treat PRLoma
○ Galactorrhea
○ Amenorrhea/Hypogonadism (if bothersome, could observe if isolated symptom)
○ DESIRE Planning pregnancy
○ Visual field deficits
○ If medication-induced and the med cannot be stopped or substituted and symptomatic (indication for surgery)
○ If impact on bone health (low BMD) + hypogonadotropic hypogonadism
○ Pituitary macroadenoma (not appropriate for observation alone)
Adv/Disadv of dopamine agonists in PRLoma
Bromocriptine
§ Advantage: reduces adenoma size effectively
§ Disadvantage: nausea (++), not as effective at lowering prolactin levels as cabergoline, given daily
Cabergoline
§ Advantages: only administered once or twice a week, higher rates of success suppressing prolactin, better tolerated
§ Disadvantage: risk of valvular heart disease (seen at high doses used in Parkinson’s tx)
TSH B subunit - genes needed
POUF1
GATA2
stimulants of TSH secretion
- TRH
- Low T3
○ PTU - Low T4
○ Iodine Def - Leptin
inhibitors of TSH secretion
- SRIF
- T3 > T4
- Glucocorticoids
- Dopamine (acutely)
- Fasting/Starvation
- Antiepileptics
- Certain cytokines
ACTH stim by?
CRH
AVP
ACTH prod cells
Corticotrophs
key genes for ACTH
TBX19
TPIT
what R does ACTH bind
MC1R -> hyperpigmentation
MC2R -> adrenal steroidogenesis
2 neurons ADH is made
magnocellular -> sends ADH to post pit
parvocellular -> sends ADH to ant pit -> enhances ACTH secretion
2 most imp gene GnRH devel
KAL1
PROK2