The pituitary gland sits in the sella turcica at the base of the brain, just below the optic chiasm, and is controlled by the hypothalamus.

• Anterior pituitary secretes GH (growth hormone), prolactin, ACTH, TSH, FSH and LH
• Posterior pituitary stores and releases antidiuretic hormone (ADH, arginine vasopressin, AVP) and oxytocin, which are made in the hypothalamus. AVP makes the kidney collecting ducts reabsorb water, concentrating urine

Pituitary disorders arise from hormone excess (usually a functioning adenoma), hormone deficiency (hypopituitarism), or mass effect from a tumor.

Pituitary adenomas (pituitary neuroendocrine tumors)

• Prolactinoma — the most common functioning adenoma. Women: amenorrhea, galactorrhea, infertility. Men: decreased libido, erectile dysfunction, and often larger tumors at diagnosis
• GH-secreting adenoma — acromegaly in adults (after growth plates close); gigantism in children
• ACTH-secreting adenoma — Cushing disease (see Topic 60)
• Non-functioning adenomas — present with mass effect or hypopituitarism

Mass effect — headache and visual field loss: upward growth compresses the optic chiasm, where fibers from the nasal half of each retina cross, causing bitemporal hemianopia (loss of the outer, temporal visual fields of both eyes).

Hypopituitarism — loss of one or more pituitary hormones from tumor, surgery, radiation, head injury, or postpartum hemorrhage (Sheehan syndrome). ACTH deficiency (secondary adrenal insufficiency) is the most dangerous — clients cannot mount a cortisol stress response.

Water balance disorders

2022 renaming — to prevent dangerous confusion with diabetes mellitus, international endocrine societies renamed central diabetes insipidus as arginine vasopressin deficiency (AVP-D) and nephrogenic diabetes insipidus as arginine vasopressin resistance (AVP-R). The old names are still widely used in parentheses; recognize both.

Acromegaly — enlarged hands and feet (rings and shoes no longer fit), coarse facial features, prominent jaw and brow, widened tooth spacing, enlarged tongue, deep voice, joint pain, sweating, sleep apnea, hypertension, glucose intolerance, cardiomyopathy.

Hypopituitarism — fatigue, cold intolerance, weight change, loss of libido, amenorrhea, loss of body hair, pale skin, hypotension, hypoglycemia; adrenal crisis under stress.

SIADH — symptoms follow the sodium level and speed of fall: headache, nausea, weakness, confusion, lethargy, muscle cramps; seizures and coma with severe or rapid hyponatremia.

AVP deficiency / resistance — polyuria, nocturia, intense thirst (polydipsia), preference for cold water; dehydration, hypotension, tachycardia, and hypernatremic confusion if the client cannot drink freely (e.g., after surgery, unconscious).

After pituitary surgery — monitor visual fields, mental status, urine output, and nasal drainage.

• Pituitary MRI — adenoma size and chiasm compression
• Formal visual field testing
• Hormone panel for any pituitary mass: prolactin, IGF-1, morning cortisol and ACTH, TSH and free T4, LH/FSH, testosterone or estradiol, and sodium. Assessing the cortisol (ACTH) axis is a safety priority before surgery, because untreated adrenal insufficiency can cause crisis — and glucocorticoid is replaced before thyroid hormone (thyroid hormone first increases cortisol clearance and can precipitate crisis)
• Acromegaly: elevated IGF-1; GH fails to suppress during an oral glucose tolerance test
• Prolactinoma: elevated prolactin (exclude pregnancy, hypothyroidism, and dopamine-blocking drugs such as antipsychotics and metoclopramide)
• SIADH: serum sodium < 135 mEq/L (mmol/L), serum osmolality < 275 mOsm/kg, urine osmolality > 100 mOsm/kg, urine sodium > 30 mEq/L (mmol/L), normal volume status, and normal thyroid and adrenal function
• AVP-D vs. AVP-R: high serum sodium/osmolality with dilute urine; copeptin measurement (after hypertonic saline or arginine stimulation) is increasingly used, or a supervised water deprivation test — then desmopressin is given: urine concentrates in AVP deficiency, but not in AVP resistance. During water deprivation, weigh hourly and stop if weight falls > 3% or sodium rises above normal

Prolactinoma — dopamine agonists are first-line, even for large tumors

• Cabergoline (preferred — better tolerated, twice weekly) — nausea, dizziness, orthostatic hypotension; high doses (as in Parkinson disease) are linked to heart valve disease; impulse-control disorders
• Bromocriptine — nausea, orthostatic hypotension and dizziness/syncope at the start (begin with a low bedtime dose), headache; take with food to reduce nausea; often chosen when pregnancy is planned
• Do not stop without the provider; prolactin and MRI monitor response

Acromegaly

• Transsphenoidal surgery first-line
• Somatostatin analogs (octreotide, lanreotide) — GI upset, gallstones, bradycardia, glucose changes (hypo- or hyperglycemia); pegvisomant (GH receptor blocker — liver tests); radiation
• Ongoing screening for diabetes, hypertension, sleep apnea, colon polyps

Hypopituitarism — lifelong replacement: hydrocortisone (with stress dosing), levothyroxine (dose by free T4, not TSH), sex hormones, and GH in selected adults (adult GH deficiency increases visceral fat, dyslipidemia, and cardiovascular risk — monitor lipids, BP, glucose, and bone density during therapy)

SIADH

• Treat the cause (stop offending drug, treat tumor or infection)
• Fluid restriction — often < 800–1,000 mL/day — first-line for mild to moderate cases
• Severe symptoms (seizures, coma): 3% hypertonic saline bolus in a monitored setting (e.g., 100–150 mL over 10–20 minutes, repeated if needed; aim for an initial rise of 4–6 mmol/L)
• Correction limit: raise sodium no more than about 8–10 mEq/L (mmol/L) in 24 hours (a stricter maximum of 8 mmol/L in 24 hours in high-risk clients — alcohol use, malnutrition, hypokalemia, liver disease) to avoid osmotic demyelination syndrome (dysarthria, dysphagia, paralysis, "locked-in" state — often appears days later)
• Other options: oral urea, salt tablets with loop diuretic, tolvaptan (vasopressin receptor antagonist) — start in hospital with close sodium checks (overly rapid correction), liver injury (limit to 30 days, avoid in liver disease), thirst; do not combine with fluid restriction at start; avoid with strong CYP3A4 inhibitors
• Loop diuretics are not routine and thiazides worsen hyponatremia

AVP deficiency (central DI)

• Desmopressin (DDAVP) — intranasal, oral, sublingual, or injection. Main risk: water retention and hyponatremia — monitor sodium, weight, and output; teach clients to drink only to thirst; headache, nausea, confusion suggest hyponatremia
• Free access to water; IV hypotonic fluids for hypernatremia per prescription, correcting slowly (chronic hypernatremia: lower sodium by no more than about 10–12 mmol/L in 24 hours — cerebral edema risk)

AVP resistance (nephrogenic DI) — treat cause (e.g., stop lithium if possible, correct calcium and potassium), thiazide diuretics (paradoxically reduce urine output), low-sodium and low-protein diet, NSAIDs in selected cases; desmopressin does not work.

Listed in priority order.

1. Neurologic and airway safety — seizure precautions in severe hyponatremia; neuro checks; airway protection for decreased consciousness
2. Strict intake and output and daily weight — the key monitoring for post-pituitary-surgery AVP deficiency and for SIADH
   • Report urine output > about 200–250 mL/h for 2 consecutive hours or low specific gravity after pituitary surgery
   • Note that water balance after pituitary surgery can shift — AVP deficiency, then transient SIADH, then possibly permanent AVP deficiency (a "triphasic" pattern)
3. Monitor sodium closely — every 2–6 hours during active correction; report rapid changes
4. SIADH: enforce fluid restriction (spread allowance across the day), oral care, sugar-free gum or candy for thirst; include IV fluids and medications in the total
5. After transsphenoidal surgery
   • Head of bed elevated about 30°
   • Avoid coughing, sneezing, nose blowing, straining, bending forward, and drinking through straws — these raise intracranial pressure or disrupt the repair
   • Mouth care without toothbrushing over the incision (usually about 10 days or as instructed)
   • Watch for CSF leak: clear nasal drainage, postnasal drip, salty taste, positional headache; a halo sign on gauze; send fluid for beta-2 transferrin testing (glucose testing is unreliable)
   • Visual field and acuity checks; glucocorticoid replacement as prescribed (adrenal crisis risk)
6. Hypopituitarism: give hydrocortisone on schedule; stress doses for illness or procedures
7. Medication safety: orthostatic precautions with dopamine agonists; glucose checks with somatostatin analogs

• Hormone replacement is usually lifelong; do not stop suddenly
• Adrenal insufficiency from pituitary disease: sick-day rules (increase hydrocortisone during illness as instructed), injection kit, medical alert identification
• Desmopressin: take as prescribed, drink only when thirsty, weigh daily; report headache, nausea, confusion, or rapid weight gain (low sodium), or return of heavy urination (under-dosing); nasal congestion reduces intranasal absorption
• SIADH: follow fluid limits, count all liquids (soups, ice); weigh daily; avoid drugs that worsen it; report headache, confusion, or muscle cramps
• Dopamine agonists: rise slowly (orthostatic hypotension, especially early), take with food, avoid driving until response is known; bromocriptine and cabergoline can restore fertility quickly — discuss contraception or pregnancy plans
• After transsphenoidal surgery: no nose blowing, bending, or heavy lifting for several weeks; sneeze with mouth open; report clear nasal drainage, fever, stiff neck (meningitis), or vision change
• Adult GH therapy: regular checks of lipids, BP, glucose, and bone density

• Pituitary apoplexy — sudden hemorrhage into an adenoma: sudden severe headache, vision loss, eye movement palsy, altered consciousness, adrenal crisis — emergency (steroids, possible surgery)
• Adrenal crisis in hypopituitarism under stress
• Severe hyponatremia — seizures, coma, respiratory arrest
• Osmotic demyelination syndrome from over-rapid sodium correction
• Hypernatremic dehydration in AVP deficiency when the client cannot drink
• CSF leak and meningitis after transsphenoidal surgery
• Permanent vision loss from chiasm compression

• Pituitary tumor compressing the optic chiasm → bitemporal hemianopia (loss of outer/temporal fields of both eyes)
• Prolactinoma: amenorrhea and galactorrhea in women; dopamine agonists first-line (cabergoline preferred); bromocriptine → orthostatic hypotension, take with food
• Acromegaly: enlarged hands and feet, coarse features; high IGF-1, GH not suppressed by glucose
• Any pituitary mass: check cortisol axis; replace glucocorticoid before thyroid hormone
• SIADH: too much ADH → low sodium, concentrated urine, low output → fluid restriction; 3% saline for severe symptoms
• Do not correct sodium faster than about 8–10 mEq/L in 24 hours (osmotic demyelination)
• 2022 rename: central DI = AVP deficiency (AVP-D); nephrogenic DI = AVP resistance (AVP-R)
• AVP deficiency: large volume dilute urine (SG < 1.005), thirst, high sodium → desmopressin (risk: hyponatremia — drink to thirst)
• After pituitary surgery: strict I&O for AVP deficiency; no coughing, nose blowing, or bending; clear drainage → test for CSF (beta-2 transferrin)
• Hypopituitarism under stress → adrenal crisis
• Adult GH deficiency → monitor BP and lipids (cardiovascular risk)