Anterior pituitary questions love to hide in plain sight: a vague postpartum history, a pituitary macroadenoma with bitemporal hemianopsia, or a medication that quietly alters dopamine tone. If you can instantly recall what the anterior pituitary makes, how it’s regulated, and what “kills” it, you’ll grab easy points on Step 1 and Step 2.
Tip #1: Lock in the “What” with one clean mnemonic (and a visual)
The hormones: FLAT PEG
- FSH
- LH
- ACTH
- TSH
- Prolactin
- Endorphins (from POMC; testable tie-in with ACTH)
- GH
Quick “visual” map (high-yield layout)
Think of the anterior pituitary as two teams:
Tropic hormones (target other endocrine glands):
- TSH → thyroid
- ACTH → adrenal cortex
- FSH/LH → gonads
Direct-acting:
- Prolactin → breast (milk production)
- GH → liver (IGF-1) + many tissues
One-liner:
Most anterior pituitary hormones are tropic (they stimulate other glands), while prolactin and GH act more directly on tissues.
USMLE pearls
- POMC cleavage → ACTH and MSH: explains hyperpigmentation in primary adrenal insufficiency (Addison) and sometimes ectopic ACTH.
- TSH is a glycoprotein, like FSH, LH, hCG (classic association).
Tip #2: Master regulation with the “Dopamine is the brake” rule
If you remember just one regulatory fact, make it this:
Dopamine tonically inhibits prolactin
- Hypothalamus → dopamine → inhibits prolactin
- Suckling → ↓ dopamine → ↑ prolactin
One-liner:
Prolactin is the only anterior pituitary hormone under predominant tonic inhibition (dopamine).
Rapid regulation table (memorize-worthy)
| Anterior pituitary hormone | Hypothalamic regulator(s) | High-yield “exam behavior” |
|---|---|---|
| Prolactin | ↓ by dopamine, ↑ by TRH | Stalk effect (↓ dopamine delivery) → ↑ prolactin |
| TSH | ↑ by TRH, ↓ by somatostatin | Primary hypothyroid → ↑ TRH can also ↑ prolactin |
| ACTH | ↑ by CRH | Cushing disease vs ectopic ACTH vs adrenal tumor patterns |
| GH | ↑ by GHRH, ↓ by somatostatin | Acromegaly: ↑ IGF-1; glucose suppresses GH in normal physiology |
| FSH/LH | ↑ by GnRH (pulsatile) | Continuous GnRH → downregulation → ↓ FSH/LH (e.g., leuprolide) |
USMLE pearls
- Pituitary stalk compression (macroadenoma) classically causes:
- ↑ prolactin (loss of dopamine inhibition)
- ± decreased other pituitary hormones (due to mass effect)
- Antipsychotics (D2 blockers) → hyperprolactinemia → galactorrhea, amenorrhea, infertility, decreased libido.
- TRH increases prolactin: primary hypothyroidism can present with galactorrhea + amenorrhea due to ↑ TRH → ↑ prolactin.
Tip #3: Predict lesions with one vascular fact (and two “can’t-miss” syndromes)
Key anatomy: the anterior pituitary depends on portal blood
The anterior pituitary is supplied mainly by the hypothalamic–hypophyseal portal system, making it vulnerable when blood flow drops.
One-liner:
Anterior pituitary is “portal-dependent,” so ischemia hits it hard—think postpartum hemorrhage → Sheehan syndrome.
Two high-yield clinical hitters
Sheehan syndrome (postpartum pituitary infarction)
- Trigger: severe postpartum hemorrhage
- Mechanism: enlarged pituitary in pregnancy + hypoperfusion → ischemic necrosis
- Classic findings:
- Failure to lactate (↓ prolactin) = early clue
- Amenorrhea (↓ FSH/LH)
- Hypothyroid symptoms (↓ TSH)
- Adrenal insufficiency symptoms (↓ ACTH)
Pituitary adenoma patterns
- Prolactinoma: most common functional pituitary adenoma
- Symptoms: galactorrhea, amenorrhea/infertility, hypogonadism
- Tx: cabergoline or bromocriptine (dopamine agonists)
- Macroadenoma mass effect:
- Bitemporal hemianopsia (optic chiasm compression)
- Headaches
- “Stalk effect” → mild/moderate ↑ prolactin
USMLE pearls
- Prolactin level can help distinguish:
- Very high prolactin often suggests prolactinoma
- Mild–moderate elevation can be stalk effect or meds
- Pituitary apoplexy (hemorrhage into adenoma): sudden headache + vision changes + hormonal collapse (Step 2 favorite emergency vignette).
15-second recap (shareable)
- FLAT PEG = anterior pituitary hormones (tropic vs direct-acting helps organize).
- Dopamine inhibits prolactin (stalk effect, antipsychotics, hypothyroid via TRH).
- Portal blood supply makes anterior pituitary ischemia-prone → Sheehan postpartum; macroadenomas → bitemporal hemianopsia.