Galanin
A neuropeptide first found in pig intestine that modulates nerve signalling, pituitary hormones and more
Galanin was isolated in 1983 from porcine intestine, a 29-amino-acid peptide with an amidated C-terminus; the human form has 30. It modulates neurotransmission in brain and nerves through three receptors and, given to people, raises growth hormone and prolactin. It is a research molecule, not a medicine.
What is it?
Galanin's first known actions were contracting gut smooth muscle and modulating nerve transmission. Three decades on, reviews link the galanin system to pain, mood, epilepsy, neurodegeneration, diabetes and cancer, mostly from animal and tissue work.
In people, intravenous galanin raised basal growth hormone and prolactin, and comparing full-length galanin with a shortened form pointed to different receptors for each effect. Genetic variants in galanin and its first receptor showed no role in early-onset obesity or fat intake, and tumour studies have mapped its receptors in human tissue. In colorectal cancer, high tumour galanin marked a worse prognosis in stage II disease (overall-survival hazard ratio 7.31), and silencing it in cultured cancer cells slowed their growth and invasion.
Most of what is known in people comes from 1990s infusion studies. A 60-minute infusion of human galanin at 80 pmol/kg per minute lowered noradrenaline and raised heart rate in healthy men, and damped the noradrenaline surge during low blood sugar. Galanin raised growth hormone in healthy women and boosted the response to GHRH in older adults to youthful levels, but did nothing in people with active acromegaly. Yet blood galanin shows no daily rhythm, so at normal levels it probably does not steer growth hormone at all. Its effect on growth hormone runs through somatostatin: it almost doubled the GH response to GHRH in short children, and pyridostigmine did not add to its effect; it restored a blunted response in obese children; and in eight women with anorexia nervosa it raised GH twice as much as in controls and, unlike in them, raised prolactin. Severe orthostatic stress drives blood galanin up several-fold, from about 26-39 to 186 pg/mL, more in women than in men.
Mood is the newer thread. In 10 people with depression already on trimipramine, four hourly 50 µg intravenous doses of galanin improved depression scores over the morning more than placebo, which the authors called preliminary. In mice, galanin released from noradrenergic neurons was needed for longer-lasting anxiety after stress. In type 2 diabetes, pooled studies find galanin raised in the blood, though on very low-certainty evidence. In a randomised placebo-controlled trial of psilocybin for major depression, the drug lowered galanin and noradrenaline in cerebrospinal fluid.
Mechanism of Action
Galanin is a neuropeptide (30 amino acids in humans) made in the brain, gut and nerves, including noradrenergic neurons, and acting on three receptors, GAL1 to GAL3.
Growth hormone
Infusions raise growth hormone and boost the response to GHRH, including in older adults.
Sympathetic nerves
It lowers noradrenaline release and raises heart rate in people.
Mood and stress
Intravenous doses improved depression scores in one small trial; in mice it sustains anxiety after stress.
Metabolism
Blood levels are higher in type 2 diabetes, on very low-certainty evidence.
Published Research
Studies read from their PubMed abstracts, with one review.
Intravenous galanin in depression
In 10 patients with depression on a stable dose of trimipramine, four hourly intravenous doses of 50 µg galanin improved depression scores over the morning more than placebo in a double-blind crossover design, and shifted the sleep EEG towards later REM sleep. The authors call it preliminary evidence.
Sympathetic outflow in healthy men
In eight healthy men, a 60-minute infusion of human galanin at 80 pmol/kg per minute lowered noradrenaline lying down and after standing, raised heart rate and blunted the usual blood pressure rise on standing.
Catecholamines during hypoglycaemia
Human galanin infusion damped the noradrenaline surge during insulin-induced hypoglycaemia, but not the adrenaline response, and it raised resting heart rate and exaggerated the heart-rate rise during hypoglycaemia without changing blood pressure.
Pituitary hormones in young women
In seven healthy young women, galanin infusion raised growth hormone but did not change spontaneous prolactin, LH, FSH, TSH, ACTH or cortisol.
Prolactin in women
In six healthy women, galanin enhanced the prolactin response to arginine and TRH but not to the dopamine blocker metoclopramide, which argues against galanin acting by lowering dopamine tone.
Growth hormone in acromegaly
A porcine galanin infusion of 8 µg/kg per hour raised growth hormone in healthy volunteers and in people whose acromegaly had been cured by surgery, but not in people with active acromegaly, a difference the authors suggest could help study the disease.
Older and younger adults
Galanin boosted the growth hormone response to GHRH in both younger and older adults, and in older people it brought the blunted response back up to the level seen in younger adults given GHRH alone.
No daily rhythm in blood levels
Plasma galanin in healthy people showed no circadian rhythm, which led the authors to conclude that circulating galanin at normal levels probably does not regulate growth hormone, despite the rise seen after infusions.
Psilocybin lowered it in spinal fluid
In a secondary analysis of a randomised placebo-controlled trial of psilocybin therapy for major depressive disorder, with cerebrospinal fluid and blood biomarkers, psilocybin selectively lowered CSF galanin and noradrenaline, which the authors read as a pharmacodynamic signature of the treatment.
Short children: synergy with GHRH
In 15 children with short stature, galanin infusion (15 µg/kg per hour) with GHRH raised growth hormone more than GHRH alone (peak 73.1 against 38.9 ng/mL), more than the sum of the two given separately, while pyridostigmine did not add to galanin's effect, supporting a mechanism through endogenous somatostatin.
Obese children: a blunted response restored
In five obese children and seven controls, the growth hormone responses to galanin and to GHRH were blunted in obesity, but galanin given with GHRH raised the obese children's response to the level the controls reached with GHRH alone.
Anorexia nervosa: exaggerated GH, new prolactin
In eight women with anorexia nervosa, a 500 µg galanin infusion raised growth hormone to a peak of 27.4 against 13.6 µg/L in healthy controls, while GHRH responses did not differ, and galanin raised prolactin in the patients (peak 18.0 µg/L) but not in the controls.
Orthostatic stress: several-fold higher
In 26 healthy adults taken to presyncope by head-up tilt and lower-body negative pressure, plasma galanin rose from 26 (men) and 39 pg/mL (women) to about 186 pg/mL, more in women (4.9-fold) than men (3.5-fold), whether or not they had trained on a human-powered centrifuge, and only loosely tracked vasopressin.
Colorectal cancer: a marker of relapse
Comparing 56 patients with stage II-III colorectal cancer who relapsed with 56 who did not, high tumour galanin expression was linked to recurrence, and in stage II to worse 5-year overall (hazard ratio 7.31) and recurrence-free survival (3.99), but not in stage III; silencing galanin in cultured cancer cells cut their proliferation and invasion (cell work).
The discovery
Isolated from porcine intestinal extract by detecting its C-terminal amide, galanin proved to be 29 amino acids long and contracted rat smooth-muscle preparations.
Pituitary hormones in people
Intravenous human galanin(1-30) raised basal growth hormone (AUC 960 against -110 on saline) while galanin(3-30) did not, suggesting different receptor subtypes for its growth hormone and prolactin effects.
Genes and obesity
Screening the galanin and GALR1 genes in obese children and adolescents and their parents found no variant playing a major role in early-onset obesity or dietary fat intake.
Bile duct cancer tissue
In human bile duct and perihilar cholangiocarcinoma tissue, galanin and GAL3 receptor expression in tumour cells were associated with survival, suggesting possible biomarkers.
Three decades of galanin
A review of galanin, galanin-like peptide and alarin, their receptors and their roles in pain, mood disorders, epilepsy, neurodegeneration, diabetes and cancer.
Depression
A review of galanin and galanin(1-15) in depression-like behaviour, highlighting interactions between galanin receptors and serotonin 5-HT1A receptors as a possible treatment target.
Alzheimer disease
A review noting that galanin and its receptors are overexpressed in limbic regions in Alzheimer disease, where galanin may both inhibit cholinergic transmission and protect neurons.
Glioma and pituitary tumours
In human glioma and pituitary adenoma tissue, galanin receptors appeared on tumour-associated immune cells, especially macrophages, pointing to galanin signalling in the tumour environment.
Its structure
Structural work found human galanin, a 30-residue peptide pursued for analgesics, antidepressants and anticonvulsants, adopts an irregular secondary structure whose C-terminal region helps pre-organise the receptor-binding site.
Galanin in type 2 diabetes, pooled
A meta-analysis found circulating galanin higher in type 2 diabetes than in controls, with moderate heterogeneity, but rated the certainty of the evidence very low.
Stress and anxiety in mice
In mice, noradrenaline drove acute anxiety-like behaviour after stress, while galanin released from the same noradrenergic neurons was needed for the longer-lasting anxiety that developed after a stressor.
Dosing Data
Galanin is not an approved medicine. Every dose on record is a research infusion or bolus given under supervision.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
Side Effects & Contraindications
Reported Side Effects
From the human infusion study.
Contraindications & Cautions
Not a medicine.
Legal Status
Not a medicine.
Frequently Asked Questions
?Is galanin a drug?
No. It is studied as a signalling peptide; no galanin product is approved.
?What does it do in people?
Given intravenously, it raised growth hormone and prolactin in a 2000 study.
?Is human galanin the same as pig galanin?
Not quite: the porcine peptide first isolated has 29 amino acids, the human one 30.
?Why are drug developers interested?
Reviews and structural studies point to galanin receptors as targets for pain, depression and epilepsy medicines, but none has been approved.
?Has galanin been tested for depression?
In one small trial. Ten patients on trimipramine received four hourly 50 µg intravenous doses or placebo, and depression scores improved more over the morning with galanin. The authors called it preliminary.
?Does galanin raise growth hormone?
When infused, yes: in healthy women, older adults and people cured of acromegaly. But blood levels have no daily rhythm, so normal circulating galanin probably does not control growth hormone.
References
- [pubmed] Tatemoto K, et al. "Galanin - a novel biologically active peptide from porcine intestine." FEBS Lett, 1983;164(1):124-8. PMID: 6197320.
- [clinical-trial] Todd JF, et al. "The differential effects of galanin-(1-30) and -(3-30) on anterior pituitary hormone secretion in vivo in humans." Am J Physiol Endocrinol Metab, 2000;278(6):E1060-6. PMID: 10827009.
- [pubmed] Schäuble N, et al. "Human galanin (GAL) and galanin 1 receptor (GALR1) variations are not involved in fat intake and early onset obesity." J Nutr, 2005;135(6):1387-92. PMID: 15930442.
- [pubmed] Huber S, et al. "Galanin System in the Human Bile Duct and Perihilar Cholangiocarcinoma." Cells, 2023;12(13). PMID: 37443714.
- [review] Lang R, et al. "Physiology, signaling, and pharmacology of galanin peptides and receptors: three decades of emerging diversity." Pharmacol Rev, 2015;67(1):118-75. PMID: 25428932.
- [review] Millón C, et al. "The neuropeptides Galanin and Galanin(1-15) in depression-like behaviours." Neuropeptides, 2017;64:39-45. PMID: 28196617.
- [review] Counts SE, et al. "Galanin in Alzheimer disease." Mol Interv, 2003;3(3):137-56. PMID: 14993421.
- [pubmed] Falkenstetter S, et al. "Galanin System in Human Glioma and Pituitary Adenoma." Front Endocrinol (Lausanne), 2020;11:155. PMID: 32265844.
- [pubmed] Wilkinson RE, et al. "The neuropeptide galanin adopts an irregular secondary structure." Biochem Biophys Res Commun, 2022;626:121-128. PMID: 35994823.
- [pubmed] Murck H, et al. "Intravenous administration of the neuropeptide galanin has fast antidepressant efficacy and affects the sleep EEG." Psychoneuroendocrinology, 2004;29(9):1205-11. PMID: 15219645.
- [pubmed] degli Uberti EC, et al. "Human galanin reduces plasma norepinephrine levels in man." J Clin Endocrinol Metab, 1995;80(6):1894-8. PMID: 7539818.
- [pubmed] degli Uberti EC, et al. "Effect of human galanin on the response of circulating catecholamines to hypoglycemia in man." Eur J Endocrinol, 1995;133(6):723-8. PMID: 8548058.
- [pubmed] Arvat E, et al. "Effect of galanin on basal and stimulated secretion of prolactin, gonadotropins, thyrotropin, adrenocorticotropin and cortisol in humans." Eur J Endocrinol, 1995;133(3):300-4. PMID: 7581945.
- [pubmed] Grottoli S, et al. "Galanin positively modulates prolactin secretion in normal women." J Endocrinol Invest, 1996;19(11):739-44. PMID: 9061507.
- [pubmed] Cuerda C, et al. "Growth hormone secretory response to intravenous galanin infusion in acromegalic patients." Exp Clin Endocrinol Diabetes, 1998;106(1):68-73. PMID: 9516063.
- [pubmed] Cremagnani L, et al. "Potentiating effect of galanin on GHRH-induced GH release. Comparison between old and young subjects." Horm Metab Res, 1996;28(2):101-4. PMID: 8867907.
- [pubmed] Ceresini G, et al. "Evaluation of the circadian profile of peripheral plasma galanin concentrations in normal subjects." Life Sci, 2002;70(22):2657-64. PMID: 12269392.
- [pubmed] Mahat RK, et al. "Neuropeptide Alterations in Type 2 Diabetes Mellitus: A Meta-Analysis of Circulating Spexin and Galanin Levels." Endocrinol Diabetes Metab, 2026;9(5):e70303. PMID: 42573161.
- [pubmed] Tillage RP, et al. "Co-released norepinephrine and galanin act on different timescales to promote stress-induced anxiety-like behavior." Neuropsychopharmacology, 2021;46(8):1535-1543. PMID: 33911187.
- [pubmed] Paslawski W, et al. "CSF galanin and noradrenaline downregulation by psilocybin therapy in major depressive disorder." Neuropsychopharmacology, 2026;51(10):1898-1901. PMID: 42414566.
- [pubmed] Loche S, et al. "Evidence for involvement of endogenous somatostatin in the galanin-induced growth hormone secretion in children." Pediatr Res, 1990;27(4 Pt 1):405-7. PMID: 1692988.
- [pubmed] Loche S, et al. "The effect of galanin on baseline and GHRH-induced growth hormone secretion in obese children." Clin Endocrinol (Oxf), 1990;33(2):187-92. PMID: 1699689.
- [pubmed] De Marinis L, et al. "Effects of galanin on growth hormone and prolactin secretion in anorexia nervosa." Metabolism, 2000;49(2):155-9. PMID: 10690937.
- [pubmed] Hinghofer-Szalkay HG, et al. "Circulatory galanin levels increase severalfold with intense orthostatic challenge in healthy humans." J Appl Physiol (1985), 2006;100(3):844-9. PMID: 16322373.
- [pubmed] Nagayoshi K, et al. "Galanin plays an important role in cancer invasiveness and is associated with poor prognosis in stage II colorectal cancer." Oncol Rep, 2015;33(2):539-46. PMID: 25504183.
Sources & Citations
Studies were read from their PubMed abstracts. Animal findings are labelled as such. Read October 16, 2026.
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