You’re doing a question on pituitary adenomas, you feel good about the diagnosis… and then you get burned by a distractor that was also kind of true. This is exactly why pituitary q-bank questions are so high-yield: they test diagnosis and the logic of why other tempting endocrine answers don’t fit. Let’s break down two classics—prolactinoma and GH-secreting adenoma—in the “every answer choice matters” style.
Tag: Endocrine > Hypothalamus & Pituitary
The Core Framework (How Step Exams Want You to Think)
When you see pituitary pathology, your mental flowchart should be:
- Hyperfunction vs hypofunction (hormone excess vs mass effect)
- Which hormone is elevated?
- Is it pituitary-driven or peripheral? (e.g., ACTH vs cortisol source)
- Any mass effect symptoms? (headache, bitemporal hemianopsia, cranial nerve palsies if cavernous sinus)
- What’s the next best test? (labs → MRI; sometimes dynamic testing)
- What’s the treatment? (medical vs surgical)
A key board favorite: Prolactin is under tonic inhibition by dopamine. So anything that decreases dopamine delivery (stalk effect) can raise prolactin—usually mildly.
Vignette #1: Prolactinoma
Clinical Stem
A 29-year-old woman presents with 6 months of amenorrhea and intermittent milky nipple discharge. She has decreased libido and occasional headaches. Pregnancy test is negative. Labs show:
- Prolactin: elevated
- TSH: normal
- FSH/LH: low-normal
MRI reveals a pituitary microadenoma.
The Correct Answer: Prolactinoma
Why it fits (high-yield):
- Galactorrhea + amenorrhea (and infertility) are classic.
- Hyperprolactinemia suppresses GnRH → ↓ LH/FSH → hypogonadism symptoms.
- Microadenomas (<10 mm) can have minimal mass effect.
Best initial treatment (board-standard)
Dopamine agonist (first-line):
- Cabergoline (often preferred: better tolerated, longer acting)
- Bromocriptine (also used; historically common)
Mechanism: D2 agonism → ↓ prolactin secretion and often shrinks tumor size.
Why Every Distractor Is Wrong (and How It Tries to Trick You)
Distractor A: “Primary hypothyroidism causing hyperprolactinemia”
Temptation: TRH stimulates prolactin release.
Why it’s wrong here:
- In primary hypothyroidism you’d expect ↑ TSH (and ↓ free T4).
- These patients can have hyperprolactinemia, but the vignette gives normal TSH.
High-yield pearl:
If you see hyperprolactinemia, always rule out:
- Pregnancy
- Hypothyroidism (↑ TRH)
- Medications (D2 blockers)
- Stalk effect
- Prolactinoma
Distractor B: “Medication-induced hyperprolactinemia (antipsychotics, metoclopramide)”
Temptation: Very common real-world cause.
Why it’s wrong here:
- No medication history suggesting D2 blockade.
- Medication-induced prolactin elevation is usually mild to moderate, and imaging wouldn’t show a discrete adenoma as the primary finding.
High-yield list of meds that increase prolactin:
- Typical antipsychotics (e.g., haloperidol)
- Risperidone/paliperidone
- Metoclopramide, prochlorperazine
- Verapamil (less common)
- Opioids (can contribute)
Distractor C: “Pituitary stalk compression (stalk effect)”
Temptation: Stalk effect can raise prolactin.
Why it’s wrong here:
- Stalk effect usually causes mild hyperprolactinemia (often not sky-high).
- It’s due to loss of dopamine delivery, not autonomous prolactin secretion.
- You’d expect a nonfunctioning macroadenoma or other sellar mass causing mass effect symptoms first.
Board-style clue:
Very high prolactin levels favor prolactinoma; mild elevations can be stalk effect. (Exact cutoffs vary, but Step logic is “mild vs very high.”)
Distractor D: “Nonfunctioning pituitary adenoma”
Temptation: Common pituitary tumor, causes headaches/visual field defects.
Why it’s wrong here:
- Nonfunctioning adenomas typically present with:
- Mass effect: bitemporal hemianopsia, headache
- Hypopituitarism from compression (often ↓ gonadotropins first)
- Possible mild prolactin elevation via stalk effect
- But the defining clinical feature here is galactorrhea/amenorrhea + adenoma consistent with a secreting tumor.
High-yield: Nonfunctioning adenomas are often gonadotroph adenomas (FSH/LH) but clinically “silent.”
Distractor E: “Sheehan syndrome”
Temptation: Amenorrhea + pituitary problem.
Why it’s wrong here:
- Sheehan = postpartum pituitary infarction after severe hemorrhage.
- Presents with failure to lactate (↓ prolactin), fatigue, hypotension, amenorrhea.
- This patient has galactorrhea (too much prolactin), not inability to lactate.
Prolactinoma High-Yield Summary Table
| Feature | Prolactinoma |
|---|---|
| Key symptoms | Galactorrhea, amenorrhea/infertility, ↓ libido; +/- headaches/visual defects if macro |
| Lab pattern | ↑ prolactin, ↓ GnRH → ↓ LH/FSH |
| First-line therapy | Cabergoline (or bromocriptine) |
| Imaging | Pituitary MRI |
| Complication | Hypogonadism, osteoporosis risk (chronic low estrogen/testosterone) |
Vignette #2: GH-Secreting Pituitary Adenoma (Acromegaly/Gigantism)
Clinical Stem
A 45-year-old man reports that his wedding ring no longer fits and his shoe size increased over the last few years. He has headaches, excessive sweating, and new-onset hypertension. Exam shows coarse facial features and enlarged hands. Labs show:
- IGF-1: elevated
The Correct Answer: GH-secreting pituitary adenoma (acromegaly)
Why it fits:
- Acromegaly = GH excess after epiphyseal closure
- IGF-1 is the best screening test because GH is pulsatile.
- Symptoms:
- Enlarged hands/feet, coarse facies
- Sweating, arthralgias
- Glucose intolerance/diabetes
- Hypertension, cardiomyopathy
- OSA (macroglossia, soft tissue growth)
- Mass effect symptoms possible
Best confirmatory test (classic Step move)
Oral glucose tolerance test (OGTT) with GH measurement:
- Normal: glucose suppresses GH
- Acromegaly: GH fails to suppress
Treatment (high yield)
- Transsphenoidal surgery is typical first-line for pituitary adenoma
- Medical therapy options:
- Octreotide/lanreotide (somatostatin analogs) → ↓ GH release
- Pegvisomant (GH receptor antagonist)
- Cabergoline can help in some cases (especially mixed tumors)
Why the Distractors Are Wrong (Acromegaly Edition)
Distractor A: “Carpal tunnel syndrome as the primary diagnosis”
Temptation: Acromegaly can cause carpal tunnel.
Why it’s wrong:
- Carpal tunnel is a complication, not the unifying diagnosis.
- The question’s systemic features (ring size, coarse facies, HTN, sweating) point to a hormonal cause.
Distractor B: “Hypothyroidism (myxedema)”
Temptation: Puffy face, fatigue, weight gain can mimic “coarse features.”
Why it’s wrong:
- Acromegaly causes growth of bone/soft tissue, not just edema.
- Hypothyroidism would suggest cold intolerance, bradycardia, constipation, and abnormal TSH/T4.
Distractor C: “Cushing disease”
Temptation: Pituitary tumor causing systemic disease + HTN + glucose intolerance.
Why it’s wrong:
- Cushing features: proximal muscle weakness, purple striae, easy bruising, truncal obesity, facial plethora.
- Acromegaly features: enlarged hands/feet, prognathism, coarse facies, sweating.
High-yield nuance: Some pituitary tumors can cosecrete, but Step usually gives a cleaner presentation.
Distractor D: “Ectopic GH or GHRH secretion”
Temptation: Ectopic hormone syndromes exist (especially with small cell).
Why it’s wrong (most of the time on Step):
- Most acromegaly is from pituitary adenoma.
- Ectopic GHRH (rare) can come from neuroendocrine tumors (e.g., bronchial carcinoid, pancreatic NET), often with imaging clues outside the sella.
Distractor E: “GH level is the best screening test”
Temptation: Just measure GH, right?
Why it’s wrong:
- GH is secreted in pulses, so random GH can be misleading.
- IGF-1 is stable → best screening.
Acromegaly High-Yield Summary Table
| Category | Key points |
|---|---|
| Best screening test | IGF-1 |
| Confirmatory test | OGTT: glucose fails to suppress GH |
| Common complications | Cardiomyopathy, HTN, insulin resistance/DM, OSA, colon polyps |
| Treatment | Transsphenoidal surgery ± somatostatin analog (octreotide), pegvisomant |
| Mass effect | Headache, bitemporal hemianopsia (optic chiasm compression) |
Rapid-Fire Board Pearls (Pituitary Adenomas)
- Prolactinoma: treat first-line with dopamine agonist (cabergoline/bromocriptine), not surgery (unless refractory/intolerant or emergent mass effect).
- Nonfunctioning macroadenoma: think mass effect + hypopituitarism; mild prolactin elevation via stalk effect.
- Bitemporal hemianopsia = optic chiasm compression.
- IGF-1 screens acromegaly; OGTT confirms.
- Pituitary apoplexy (sudden hemorrhage into adenoma): acute headache, visual symptoms, ophthalmoplegia → emergency steroids + neurosurgery evaluation.
- Always check pregnancy test in reproductive-age patients with amenorrhea/galactorrhea.
Q-Bank Mindset: How to Stop Missing “Obvious” Pituitary Questions
When reviewing, force yourself to justify:
- Why the correct diagnosis explains every major symptom and lab.
- Why each distractor fails at least one of:
- Time course (acute vs chronic)
- Hormone pattern
- Imaging expectation
- Pathophysiology (dopamine/TRH/stalk effect)
- Classic clinical “tell” (ring size increase, galactorrhea, bitemporal hemianopsia)
That habit is what turns pituitary from “random endocrine trivia” into free points.