Pituitary Hormone Agents
High-yield Verified · Oct 2026Learn each hormone’s brake: somatostatin for growth hormone and the gut, IGF-1 feedback for growth hormone, dopamine for prolactin. Then each drug either copies the brake, replaces the hormone, or blocks its receptor. The ADH drugs are on the Pituitary ADH Agents page.
Nursing view → administration, monitoring and patient teaching
Drugs
Mechanism
Octreotide and lanreotide are somatostatin analogs: through G protein–coupled somatostatin receptors (mainly SSTR2 and 5) they inhibit growth hormone, insulin, glucagon, TSH and gut hormones (serotonin, VIP, gastrin). Somatropin is recombinant growth hormone, acting directly and through hepatic IGF-1. Pegvisomant blocks the growth hormone receptor, lowering IGF-1. Cabergoline and bromocriptine are dopamine D2 agonists that inhibit prolactin secretion from pituitary lactotrophs.
Somatostatin: a hormone off-switch, made to last
Somatostatin acts through five G protein–coupled receptors that lower cAMP and calcium, so the target cell secretes less: it inhibits growth hormone, TSH, prolactin, insulin, glucagon and gut secretions, and it slows bile flow and pancreatic enzyme release. Natural somatostatin lasts 1 to 3 minutes in plasma; octreotide’s half-life is 1.7 to 1.9 hours, and lanreotide’s depot releases drug with a half-life of 23 to 30 days. Both act mainly through receptor subtype 2 (lanreotide also 5).
In acromegaly the analogs suppress growth hormone from the normal pituitary and from somatotroph adenomas and reduce the liver’s IGF-1 production. In carcinoid tumors and VIPomas, they inhibit release of serotonin and VIP, controlling flushing and diarrhea.
Nature runs the experiment in somatostatinoma, a tumor that secretes somatostatin: its syndrome is cholelithiasis, diabetes, weight loss and steatorrhea, because excess somatostatin decreases gallbladder emptying, suppresses insulin and inhibits pancreatic enzymes. The drugs reproduce it: gallbladder abnormalities (stones and sludge) are among the commonest reactions, hypoglycemia or hyperglycemia occurs because insulin, glucagon and growth hormone are all suppressed, and fat malabsorption causes steatorrhea. Suppressed TSH can cause hypothyroidism, and octreotide can slow the heart.
The GH–IGF-1 axis: replace it or block it
Growth hormone acts directly on its receptor and indirectly through IGF-1, secreted by the liver in response to it. Because IGF-1 does not swing with sleep, exercise or time of day the way GH does, it is the screening test for acromegaly; an equivocal result is settled by a glucose load — a GH that stays above the cutoff after glucose confirms acromegaly.
Somatropin replaces growth hormone: in children it stimulates growth at the epiphyseal plates, and in adults with deficiency it reduces fat mass and increases lean mass. Growth hormone opposes insulin, so somatropin can unmask glucose intolerance or diabetes; it retains fluid (edema, arthralgia, carpal tunnel) and can raise intracranial pressure. Because GH inhibits 11βHSD-1, the enzyme that converts cortisone to cortisol, it can unmask central hypoadrenalism or raise glucocorticoid needs. In children with Prader-Willi syndrome who are severely obese or have respiratory impairment, sudden deaths have been reported, so the airway is evaluated first.
Pegvisomant is a GH analog that binds the GH receptor and blocks endogenous GH, so IGF-1 falls. With less IGF-1 feedback, GH rises — and pegvisomant itself cross-reacts in GH assays, making GH appear falsely high. IGF-1 is therefore the only marker followed. As GH action falls, glucose tolerance may improve, so diabetic patients risk hypoglycemia, and liver tests are monitored.
Dopamine and prolactin
Prolactin secretion is tonically inhibited by dopamine from the hypothalamus. Prolactin in turn inhibits GnRH release, lowering LH and FSH — which is why hyperprolactinemia causes amenorrhea, infertility and hypogonadism. Drugs that block dopamine receptors — antipsychotics such as risperidone and haloperidol, and antiemetics such as metoclopramide — raise prolactin; risperidone can produce the largest elevations.
Cabergoline (high D2 affinity) and bromocriptine are ergot-derived dopamine agonists that suppress prolactin secretion and lactotroph proliferation, shrinking prolactinomas. Cabergoline is generally preferred: it more often normalizes prolactin and shrinks the tumor, with a more favorable adverse-effect profile, and its 63- to 69-hour half-life suits twice-weekly dosing. Bromocriptine also lowers GH in most patients with acromegaly, where dopamine agonists are less effective than somatostatin analogs and are often adjuncts. A timed-morning bromocriptine product, Cycloset, is labeled for type 2 diabetes.
The ergot structure brings cardiac valvulopathy and pleural, pulmonary, pericardial or retroperitoneal fibrosis — an echocardiogram is done before treatment and every 6 to 12 months. Raising dopaminergic tone can cause orthostatic hypotension and impulse control disorders, and D2 antagonists blunt the effect. With a macroprolactinoma on bromocriptine, visual fields are monitored for field loss from chiasmal herniation.
Comparing the drugs
Pituitary hormone agents compared
| Drug | Target | Main uses | Marker followed | Signature risk |
|---|---|---|---|---|
| Octreotide | Somatostatin receptors (mainly SSTR2) | Acromegaly; carcinoid; VIPoma | GH and IGF-1 | Gallstones; glucose swings; bradycardia; hypothyroidism |
| Lanreotide | SSTR2 and SSTR5 | Acromegaly; carcinoid syndrome; GEP-NETs | GH and IGF-1 | Gallstones; glucose swings; slowed heart rate |
| Somatropin | GH receptor (agonist) | Pediatric growth failure; adult GH deficiency | Growth; IGF-1 | Glucose intolerance; intracranial hypertension; SCFE; Prader-Willi deaths |
| Pegvisomant | GH receptor (antagonist) | Acromegaly | IGF-1 only (GH reads falsely high) | Liver test elevations; hypoglycemia in diabetes |
| Cabergoline | D2 receptor (agonist) | Hyperprolactinemic disorders | Prolactin | Valvulopathy and fibrosis; orthostatic hypotension; impulse control |
| Bromocriptine | Dopamine receptors (agonist) | Hyperprolactinemia; prolactinoma; acromegaly; type 2 diabetes (Cycloset) | Prolactin; GH and IGF-1 | Valvulopathy and fibrosis; hypotension; somnolence |
Pharmacokinetics
- Somatostatin analogs — octreotide, lanreotide
- Octreotide’s half-life is 1.7 to 1.9 hours (natural somatostatin 1 to 3 minutes), with action up to 12 hours; long-acting analogs are usually given as once-monthly intramuscular injections, and the lanreotide depot has a half-life of 23 to 30 days. Oral octreotide (Mycapssa) is taken on an empty stomach — food cut its absorption by about 90%.
- Pegvisomant — pegvisomant
- Half-life 60 to 138 hours; GH rises within two weeks as IGF-1 falls.
- Dopamine agonists — cabergoline, bromocriptine
- Cabergoline’s elimination half-life is 63 to 69 hours. Bromocriptine is a CYP3A4 substrate: strong CYP3A4 inhibitors raise its exposure and are avoided.
Uses & drug choice
- Octreotide (Sandostatin, Sandostatin LAR Depot, Bynfezia Pen) — acromegaly when surgery, radiation or bromocriptine is inadequate or not possible; severe diarrhea and flushing of metastatic carcinoid tumors; watery diarrhea of VIPomas. Oral octreotide (Mycapssa) — maintenance in acromegaly after response to octreotide or lanreotide
- Lanreotide (Somatuline Depot) — long-term treatment of acromegaly; carcinoid syndrome; unresectable, well- or moderately differentiated gastroenteropancreatic neuroendocrine tumors (to improve progression-free survival)
- Somatropin — pediatric growth failure (growth hormone deficiency, Prader-Willi syndrome, small for gestational age, Turner syndrome, idiopathic short stature) and adult growth hormone deficiency
- Pegvisomant (Somavert) — acromegaly with inadequate response to, or no option for, surgery or radiation; the goal is a normal IGF-1
- Cabergoline — hyperprolactinemic disorders, idiopathic or from pituitary adenomas, in adults
- Bromocriptine — hyperprolactinemia-associated dysfunction, prolactin-secreting adenomas and acromegaly; Cycloset: adjunct for glycemic control in type 2 diabetes
Adverse effects
- Gallstones (octreotide, lanreotide)
- Less gallbladder contractility and bile secretion — the somatostatinoma pattern.
- Hypoglycemia or hyperglycemia (octreotide, lanreotide)
- Insulin, glucagon and growth hormone are all suppressed, shifting the balance either way.
- Glucose intolerance (somatropin)
- Growth hormone opposes insulin by decreasing insulin sensitivity.
- Unmasked hypoadrenalism (somatropin)
- GH inhibits 11βHSD-1, which converts cortisone to active cortisol.
- Falsely high GH (pegvisomant)
- The drug cross-reacts in GH assays, and true GH also rises as IGF-1 feedback falls.
- Hyperprolactinemia from antipsychotics and metoclopramide
- D2-receptor blockade removes dopamine’s tonic inhibition of prolactin.
Interactions
Contraindications
- Somatropin — acute critical illness (after open-heart or abdominal surgery, multiple trauma, or acute respiratory failure) — Labeled contraindication for pharmacologic amounts of somatropin.
- Somatropin — children with Prader-Willi syndrome who are severely obese, have upper airway obstruction or sleep apnea, or severe respiratory impairment — Labeled contraindication — sudden deaths have been reported.
- Somatropin — active malignancy, active proliferative or severe non-proliferative diabetic retinopathy, or growth promotion with closed epiphyses — Labeled contraindications.
- Cabergoline or bromocriptine — history of cardiac valvular disorders or pericardial, pleural, pulmonary or retroperitoneal fibrosis; uncontrolled hypertension; ergot hypersensitivity — Labeled contraindications — the ergot dopamine agonists can cause valvulopathy and fibrosis.
- Cycloset (bromocriptine) — syncopal migraine, postpartum or lactating patients — Labeled contraindications — hypotensive episodes in syncopal migraine; serious reactions postpartum; bromocriptine inhibits lactation.
- Octreotide or lanreotide — hypersensitivity — Labeled contraindication.
- Cabergoline or bromocriptine for postpartum lactation suppression use caution — Avoided — this unapproved use of bromocriptine was associated with hypertension, stroke, myocardial infarction, seizures and death.
- Bromocriptine — severe psychotic disorders use caution — Not recommended — it may exacerbate psychosis.
High-yield
- Copy somatostatin: octreotide, lanreotide — GH, carcinoid, VIPoma; gallstones and glucose swings
- Replace GH: somatropin — growth; watch glucose, intracranial pressure, hips, Prader-Willi airway
- Block the GH receptor: pegvisomant — follow IGF-1, liver tests
- Brake prolactin: cabergoline, bromocriptine — echo for valves, ask about impulses
Practice questions
Q1A 54-year-old man with acromegaly and type 2 diabetes starts octreotide. Over the next weeks his glucose swings between low and high readings.
Which action of octreotide best explains this?
- A.It suppresses both insulin and glucagon secretion
- B.It stimulates insulin release regardless of glucose
- C.It raises growth hormone secretion
- D.It raises TSH and thyroid hormone levels
Show answer
A. It suppresses both insulin and glucagon secretion — Octreotide is an even more potent inhibitor of growth hormone, glucagon and insulin than somatostatin; by altering the balance between insulin, glucagon and GH it can cause hypoglycemia or hyperglycemia, so glucose is monitored and antidiabetic doses adjusted. It inhibits rather than stimulates insulin, lowers rather than raises growth hormone, and suppresses TSH, which can cause hypothyroidism.
Q2A 47-year-old woman with acromegaly is started on pegvisomant. At 3 months her IGF-1 is normal, but her serum GH is higher than before treatment.
How should these results be interpreted?
- A.Treatment has failed, because GH is rising
- B.IGF-1 is the marker to follow: GH rises as IGF-1 feedback falls, and pegvisomant cross-reacts in GH assays
- C.Pegvisomant stimulates GH release and should be stopped
- D.A second GH-secreting tumor has developed
Show answer
B. IGF-1 is the marker to follow: GH rises as IGF-1 feedback falls, and pegvisomant cross-reacts in GH assays — Pegvisomant blocks the GH receptor, so IGF-1 falls; GH rises, presumably from diminished inhibition as IGF-1 falls, and because pegvisomant cross-reacts in commercial GH assays, GH appears falsely elevated. IGF-1 is the only biochemical marker used to monitor response, and a normal IGF-1 is the goal of treatment. The GH rise is the expected feedback response, not a sign that the drug stimulates GH or that a new tumor has appeared.
Q3A 28-year-old woman taking risperidone for schizophrenia develops amenorrhea and galactorrhea; her prolactin is markedly elevated and pituitary imaging is normal.
What best explains her presentation?
- A.Risperidone stimulates dopamine receptors, and dopamine raises prolactin
- B.Prolactin stimulates GnRH, causing the amenorrhea
- C.Cabergoline should be added, because it blocks D2 receptors
- D.D2-receptor blockade removes dopamine’s tonic inhibition of prolactin, and prolactin suppresses GnRH
Show answer
D. D2-receptor blockade removes dopamine’s tonic inhibition of prolactin, and prolactin suppresses GnRH — Prolactin secretion is tonically inhibited by hypothalamic dopamine; neuroleptics such as risperidone raise prolactin through dopamine-receptor antagonism, and risperidone can produce the most significant elevations. Prolactin inhibits GnRH release, lowering LH and FSH, which causes the amenorrhea. Dopamine inhibits rather than stimulates prolactin, and cabergoline is a D2 agonist — one not recommended with D2 antagonists; substitution with an agent that does not raise prolactin is considered instead.
Q4A 45-year-old woman has taken cabergoline for a prolactinoma for 3 years. She now has a new heart murmur, ankle edema and exertional dyspnea.
What is the most appropriate next step?
- A.Increase cabergoline to keep prolactin suppressed
- B.Evaluate with an echocardiogram, and stop cabergoline if new valvulopathy is found
- C.Switch to bromocriptine, which carries no valve risk
- D.Add metoclopramide to relieve associated nausea
Show answer
B. Evaluate with an echocardiogram, and stop cabergoline if new valvulopathy is found — Valvular and pericardial fibrosis with cabergoline often present as heart failure; a new murmur, edema or dyspnea calls for an echocardiogram, and cabergoline is stopped for a new diagnosis of valvular regurgitation, restriction or leaflet thickening. Bromocriptine carries the same valvulopathy warning and contraindication, and metoclopramide, a D2 antagonist, is not recommended with cabergoline.
Sources
- Sandostatin (octreotide) injection — FDA label: indications, mechanism, gallbladder, glucose, thyroid, cardiac, interactions — FDA / DailyMed
- Sandostatin LAR Depot (octreotide) — FDA label — FDA / DailyMed
- Mycapssa (oral octreotide) — FDA label: acromegaly maintenance, administration, acid-suppressant interaction — FDA / DailyMed
- Bynfezia Pen (octreotide) — FDA label — FDA / DailyMed
- Somatuline Depot (lanreotide) — FDA label: indications, SSTR2/5, warnings, interactions — FDA / DailyMed
- Genotropin (somatropin) — FDA label: indications, contraindications, warnings, 11βHSD-1 — FDA / DailyMed
- Humatrope (somatropin) — FDA label — FDA / DailyMed
- Norditropin (somatropin) — FDA label — FDA / DailyMed
- Omnitrope (somatropin) — FDA label — FDA / DailyMed
- Zomacton (somatropin) — FDA label — FDA / DailyMed
- Somavert (pegvisomant) — FDA label: GH-receptor antagonism, IGF-1, liver tests, GH assay cross-reactivity — FDA / DailyMed
- Cabergoline tablets (Teva) — FDA label: D2 agonism, hyperprolactinemia, valvulopathy, fibrosis — FDA / DailyMed
- Bromocriptine mesylate (Zydus) — FDA label: prolactin, acromegaly, ergot warnings, interactions — FDA / DailyMed
- Cycloset (bromocriptine) — FDA label: type 2 diabetes, timed morning dosing, contraindications — FDA / DailyMed
- Physiology, Somatostatin — receptors, inhibitory actions, analogs — StatPearls / NCBI Bookshelf
- Physiology, Pituitary Hormones — GH and IGF-1, dopamine and prolactin — StatPearls / NCBI Bookshelf
- Acromegaly — somatostatin analogs, dopamine agonists, pegvisomant — StatPearls / NCBI Bookshelf
- Prolactinoma — dopamine agonists; cabergoline preferred — StatPearls / NCBI Bookshelf
- The use of stems in the selection of INN (-reotide, som-, -erg-) — World Health Organization
- Hyperprolactinemia — dopamine and GnRH, drug causes — StatPearls (NCBI)
By LearnDrugs
Educational summary for medical students. Always verify against current prescribing information and guidelines. Not medical advice.