Prolactinoma vs Pituitary stalk effect
How to tell Prolactinoma and Pituitary stalk effect apart when a board question makes them look alike.
Prolactinoma makes prolactin very high; stalk effect mildly raises prolactin by blocking dopamine inhibition.
Side by side
Lactotroph adenoma causing marked prolactin elevation, galactorrhea, amenorrhea or hypogonadism, infertility, low libido, and possible bitemporal hemianopia if large.
Non-prolactin sellar mass compresses the pituitary stalk, reducing dopamine inhibition and causing mild to moderate prolactin elevation.
Autonomous prolactin secretion from lactotroph tumor directly raises prolactin and suppresses GnRH.
Interrupted hypothalamic dopamine delivery removes tonic inhibition of lactotrophs without making the tumor a prolactin-secreting adenoma.
Very high prolactin, pituitary adenoma, and response to dopamine agonist support prolactinoma.
Sellar mass with modest prolactin elevation and other pituitary hormone deficits supports stalk effect.
The trap
Both can cause hyperprolactinemia and hypogonadism, so prolactin degree and mass type matter.
The repair move
For hyperprolactinemia, ask whether the mass secretes prolactin or merely blocks dopamine delivery.
Try a free question
CoreA woman has amenorrhea, galactorrhea, infertility, very high prolactin, and a pituitary lesion that shrinks after dopamine agonist therapy. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Prolactinoma. Very high prolactin with response to dopamine agonist supports prolactinoma.
Why the other choices are tempting
- B. Stalk effect usually causes modest prolactin elevation from reduced dopamine inhibition.
- C. A nonfunctioning adenoma may cause stalk effect but does not directly secrete prolactin.
- D. Sheehan syndrome causes postpartum pituitary infarction with hormone deficiencies.
- E. Primary hypothyroidism can raise TRH and prolactin but would have hypothyroid labs.
Flashcards
Tap a card to flip it.
What prolactin pattern favors prolactinoma?
Marked prolactin elevation favors a prolactin-secreting lactotroph adenoma.
What prolactin pattern favors stalk effect?
Modest prolactin elevation with a non-prolactin sellar mass favors stalk effect.
Quick answers
What is the fastest way to tell Prolactinoma from Pituitary stalk effect?
Prolactinoma makes prolactin very high; stalk effect mildly raises prolactin by blocking dopamine inhibition.
What is the key clue for Prolactinoma?
Lactotroph adenoma causing marked prolactin elevation, galactorrhea, amenorrhea or hypogonadism, infertility, low libido, and possible bitemporal hemianopia if large.
What is the key clue for Pituitary stalk effect?
Non-prolactin sellar mass compresses the pituitary stalk, reducing dopamine inhibition and causing mild to moderate prolactin elevation.
What is the common trap with Prolactinoma vs Pituitary stalk effect?
Both can cause hyperprolactinemia and hypogonadism, so prolactin degree and mass type matter.