STEPTRACKERENDOCRINE | PATHOLOGY + PHYSIOLOGY + PHARMACOLOGY | HIGH-YIELD REVIEW

Anterior Pituitary

Adenomas named by the hormone they make, the structures a large one squeezes, and every way the gland can fail.

FOCUS ON
Prolactinoma (most common functioning): galactorrhea, amenorrhea, ↓ libido → cabergoline. GH adenoma: gigantism or acromegaly, ↑ IGF-1, GH not suppressed by glucose. Macroadenomas → bitemporal hemianopia, stalk effect (↑ prolactin), hypopituitarism. Sheehan: postpartum hemorrhage → can't lactate. Apoplexy: sudden headache, vision loss, shock → steroids.
DISORDER
MECHANISM
FEATURES
CLUE · TREATMENT
Pituitary adenoma — mass effect
Macroadenoma (> 1 cm) compresses neighbors
Headache, bitemporal hemianopia (chiasm), hypopituitarism, CN III/IV/VI palsy (cavernous sinus)
Nonfunctioning/gonadotroph adenomas present this way · MEN1
Prolactinoma
most common functioning
Prolactin inhibits hypothalamic GnRH → ↓ LH/FSH
Women: galactorrhea, amenorrhea, infertility · men: ↓ libido, ED, later mass effect
Dopamine agonists (cabergoline, bromocriptine) shrink it
Other hyperprolactinemia
Loss of dopamine inhibition or ↑ TRH
Antipsychotics, metoclopramide, stalk compression, hypothyroidism, pregnancy, CKD, chest-wall stimulation
Check TSH and hCG first
Somatotroph adenoma
↑ GH → ↑ hepatic IGF-1; GNAS mutations
Children: gigantism · adults: acromegaly — coarse face, jaw protrusion, big hands/feet, macroglossia, sweating, glucose intolerance, HTN
↑ IGF-1; GH not suppressed by oral glucose · death from cardiomyopathy
Acromegaly — treatment
Remove or block GH action
Transsphenoidal surgery; octreotide (somatostatin analog); pegvisomant (GH receptor antagonist); cabergoline
Also colon polyps, carpal tunnel, sleep apnea
Corticotroph adenoma
↑ ACTH → bilateral adrenal hyperplasia
Cushing disease; often a microadenoma
Suppresses with high-dose dexamethasone
Thyrotroph adenoma
Autonomous TSH
Hyperthyroidism with ↑ TSH and ↑ T4; goiter
Rare
Pituitary apoplexy
Sudden hemorrhage/infarction of an adenoma
Thunderclap headache, visual loss, ophthalmoplegia, hypotension (acute ACTH loss)
Emergency glucocorticoids ± decompression
Sheehan syndrome
Pregnancy-enlarged pituitary infarcts after postpartum hemorrhage (hypotension)
Failure to lactate, no menses, fatigue, hypothyroidism, adrenal insufficiency
Replace cortisol before thyroid hormone
Empty sella syndrome
Arachnoid herniates into sella, flattening the gland
Usually incidental; obese women, idiopathic intracranial hypertension
Function usually normal
Craniopharyngioma
Benign tumor from Rathke pouch remnants (oral ectoderm)
Children: suprasellar calcified cystic mass ("machinery oil" fluid); bitemporal hemianopia, growth failure, DI
Calcification on CT
Other hypopituitarism
Trauma, radiation, infiltration (sarcoid, hemochromatosis, LCH), lymphocytic hypophysitis (late pregnancy)
Loss order: GH → LH/FSH → TSH → ACTH; prolactin last
ACTH loss is the dangerous one

Mechanism — what a macroadenoma presses on

UpOptic chiasm → bitemporal hemianopia
StalkDopamine blocked → ↑ prolactin
Normal glandHypopituitarism
SidewaysCavernous sinus → CN III, IV, V1, V2, VI

Prolactin is the only anterior hormone under mainly inhibitory control (dopamine) — so it rises, not falls, when the stalk is cut.

Adenoma → hormone → treatment

ADENOMA
PICTURE
TREATMENT
Prolactinoma
Galactorrhea, amenorrhea
Cabergoline, bromocriptine
Somatotroph
Acromegaly / gigantism
Surgery, octreotide, pegvisomant
Corticotroph
Cushing disease
Transsphenoidal surgery
Thyrotroph
Hyperthyroid, ↑ TSH
Surgery, octreotide
Gonadotroph / null
Mass effect
Surgery

How it's tested

COMMON CONFUSIONA large nonfunctioning adenoma can raise prolactin modestly (stalk effect) — it isn't a prolactinoma, and a dopamine agonist won't shrink it much.
THE TRAPIn panhypopituitarism, replace glucocorticoid before thyroid hormone. Thyroxine first increases cortisol metabolism and can precipitate adrenal crisis.
YOUR APPROACHSymptoms of excess (which hormone?) or deficiency (which axis?) → visual fields → MRI → confirm (IGF-1 + glucose test, prolactin, ACTH tests) → drug or surgery.

If you see… think…

Young woman with amenorrhea and milky discharge, high prolactin → prolactinoma — cabergoline
Galactorrhea on risperidone → dopamine blockade
Rings and shoes no longer fit, jaw protrudes, sweating → acromegaly
Best screening test for acromegaly → IGF-1
GH receptor antagonist → pegvisomant
Headache and loss of peripheral vision on both sides → macroadenoma compressing chiasm
Sudden headache, diplopia, hypotension in a known adenoma → pituitary apoplexy
Can't breastfeed after massive postpartum bleeding → Sheehan syndrome
Child with short stature, bitemporal hemianopia, calcified suprasellar mass → craniopharyngioma
First anterior pituitary hormone lost with compression → GH