Somatostatin is one of the body’s main brake hormones, a small protein that tells other glands and organs to slow down. It is made in several places at once, including the brain, the stomach and gut, and the pancreas.1PubMed. The somatostatin receptor in human pancreatic β-cells The natural hormone breaks down within minutes, so the treatments people are prescribed are longer-lasting lab-made copies that borrow its braking effect. For most people, somatostatin matters less as something to measure in their own blood and more as the model for drugs and scans used against certain hormone-making tumors and growth hormone excess.
Where Somatostatin Is Made and in What Forms
In the gut, somatostatin comes from cells called D cells in the lining of the stomach and the first part of the small intestine.2TeachMePhysiology. Somatostatin – Structure – Function – TeachMePhysiology In the pancreas it comes from delta cells, which sit inside the small hormone-making clusters called islets, alongside the insulin-making cells.3TeachMePhysiology. Somatostatin – Structure – Function – TeachMePhysiology In the brain, a key source is the hypothalamus, a control center at the base of the brain that oversees many hormones.4TeachMePhysiology. Somatostatin – Structure – Function – TeachMePhysiology Each site uses the hormone locally to slow its neighbors, which is why its effects reach growth, blood sugar and digestion at once.
The name comes from “somato” (body and growth) and “statin” (stopping). It was first found in the hypothalamus as the factor that stops growth hormone release.
Cells first build a larger inactive protein, then cut it into two active pieces: somatostatin-14 and somatostatin-28, named for how many building blocks each has.5PubMed. Distribution of somatostatin-14 and somatostatin-28 gastrointestinal-pancreatic cells of rats and humans The stomach, pancreas and brain nerve cells mostly finish with the shorter 14 form, while intestinal lining cells mainly finish with the longer 28 form.6PubMed. Distribution of somatostatin-14 and somatostatin-28 gastrointestinal-pancreatic cells of rats and humans The hypothalamus mostly makes the 14 form.7TeachMePhysiology. Somatostatin – Structure – Function – TeachMePhysiology Not every hormone-making cell can do this cutting, so the form produced depends on the cell type.8PubMed. Cell-specific processing of preprosomatostatin in cultured neuroendocrine cells
The somatostatin-making cells of the gut and pancreas belong to the neuroendocrine system, the family of hormone-making cells that neuroendocrine tumors grow from, which is why the hormone appears so often in those diagnoses. If you see “D cell” or “delta cell” in a report, that is the ordinary cell that makes this hormone, not a disease.
How Somatostatin Switches Cells Off
Somatostatin works by binding to receptors, receiving sites on the cell surface, and there are five types named SSTR1 to SSTR5.9PubMed. Somatostatin and its receptor family Each type is made from its own gene, and different tissues carry different mixes of them.10PubMed. Somatostatin and its receptor family That means drugs that favor one type over another can target some organs more than others.
Tumors and pituitary growths carry their own mix of receiving sites, often rich in SSTR2. A drug works best when it matches what the growth carries, which is why doctors may scan for receptors before choosing a somatostatin-like drug.
Inside the cell, all five types turn down one of the main “go” signals, a messenger chemical.11Alomone Labs. What Is Somatostatin? Function, Synthesis, and Clinical Use Most types also open channels that let potassium leave the cell and reduce the calcium entering it.12Alomone Labs. What Is Somatostatin? Function, Synthesis, and Clinical Use Cells need incoming calcium to release their hormones, so less calcium means less hormone let out. Through these signals somatostatin damps nerve signaling, hormone release, cell growth and muscle contraction in the gut.13Alomone Labs. What Is Somatostatin? Function, Synthesis, and Clinical Use Its effects are mostly reversible once the signal stops.
What Somatostatin Does in the Body
Released from the hypothalamus, somatostatin is a strong brake on growth hormone from the pituitary gland.14PubMed. Differential inhibition of growth hormone secretion by analogs selective for somatostatin receptor subtypes 2 and 5 in human growth-hormone-secreting adenoma cells in vitro This is the effect drugs use to treat growth hormone excess.
Inside the pancreas, somatostatin acts on its immediate neighbors, holding back insulin, glucagon and even its own release.15Nature Reviews Endocrinology. The somatostatin-secreting pancreatic δ-cell in health and disease The pause it causes in those cells is brief rather than lasting.16PubMed Central. The somatostatin-secreting pancreatic δ-cell in health and disease The pause lets the pancreas fine-tune how much of each hormone enters the blood after eating. After a mixed meal in lab experiments, much of its brake on insulin works indirectly, by quieting glucagon cells that would otherwise boost insulin.17PubMed Central. Somatostatin Receptors Shape Insulin and Glucagon Output within the Pancreatic Islet through Direct and Paracrine Effects So somatostatin keeps both blood-sugar hormones from overshooting rather than pushing sugar one way.
In the gut, somatostatin slows stomach acid, both by acting on nearby cells and by traveling in the blood.18PubMed. Physiological role of somatostatin in the digestive tract: gastric acid secretion, intestinal absorption, and motility It can slow how fast nutrients are absorbed and how quickly food moves through the intestine.19PubMed. Physiological role of somatostatin in the digestive tract: gastric acid secretion, intestinal absorption, and motility It also affects digestive enzyme and hormone release and helps keep the gut lining’s barrier intact.20PubMed Central. The Role of Somatostatin in the Gastrointestinal Tract
This braking explains common side effects of somatostatin-like drugs. Slowed digestion and enzyme release account for loose stools, gas and fatty stools. Slowed gallbladder and gut activity help explain why gallstones are a known risk. Effects on insulin and glucagon explain why blood sugar can shift and is checked.
Somatostatin also dampens some immune activity, such as release of an inflammatory messenger from certain white blood cells.21PubMed. The somatostatin immunoregulatory circuit present at sites of chronic inflammation In animal models of autoimmune disease and long-term inflammation, somatostatin-like drugs have helped.22PubMed. Somatostatin and somatostatin receptors in the immune system: a review This is not yet an established treatment use in people.
Why Medicine Uses Lab-Made Versions
Natural somatostatin lasts only about 3 minutes in the bloodstream before half of it is gone.23Proceedings of the Society for Experimental Biology and Medicine. Mechanisms of Antineoplastic Action of Somatostatin Analogs It would need a constant drip to have any steady effect. So drug makers designed somatostatin analogs, lab-made copies that last far longer and are more selective.24Proceedings of the Society for Experimental Biology and Medicine. Mechanisms of Antineoplastic Action of Somatostatin Analogs
“More selective” matters because natural somatostatin binds all five receptor types, so it brakes many systems at once, including ones a patient may not need slowed. Analogs are shaped to favor certain types, concentrating the effect where a tumor or pituitary growth carries those receiving sites. The selectivity is partial, so some effects on digestion, gallbladder and blood sugar still appear.
Octreotide and lanreotide are the first-generation analogs, and they mainly target the SSTR2 and SSTR5 receptors.25PubMed. Lanreotide for the treatment of acromegaly Long-acting forms such as octreotide LAR and lanreotide depot are given as injections, typically about once a month. Pasireotide is a newer analog that binds more receptor types, including SSTR1, 2, 3 and 5.26PubMed. Pasireotide in Acromegaly: An Overview of Current Mechanistic and Clinical Data
Treatment day depends on the form. Short-acting octreotide is injected under the skin, often several times a day. The long-acting forms are deep monthly injections, sometimes given by a nurse or at home. Soreness at the injection site and stomach upset in the first weeks are common and often ease.
Treating Acromegaly
Acromegaly is usually caused by a benign pituitary growth that makes too much growth hormone. Binding SSTR2 and SSTR5 on these growths lowers growth hormone release and can slow the growth’s cells.27PubMed. Lanreotide for the treatment of acromegaly
Doctors judge control using growth hormone and IGF-1, a blood marker made in response to growth hormone. Octreotide LAR controlled both in about 55 to 70% of previously treated patients.28PubMed. Octreotide long-acting release (LAR): a review of its use in the management of acromegaly That control kept improving over up to 4 years of treatment.29PubMed. Octreotide long-acting release (LAR): a review of its use in the management of acromegaly In one small comparison, IGF-1 returned to normal in about 56% on lanreotide and 70% on octreotide LAR.30PubMed. A comparison of lanreotide and octreotide LAR for treatment of acromegaly
Pasireotide gave better control than octreotide and helped some people not controlled on top doses of the older drugs.31PubMed. Pasireotide in Acromegaly: An Overview of Current Mechanistic and Clinical Data It is also used for Cushing’s disease, a pituitary condition of excess cortisol.32PubMed Central. Pasireotide—a novel somatostatin receptor ligand after 20 years of use
Years of excess growth hormone can enlarge the hands, feet and facial features, and cause joint pain, sweating and headaches. Bringing growth hormone and IGF-1 down aims to stop further progression and ease symptoms.
Expect growth hormone and IGF-1 blood tests a few months after starting or changing a dose. A normal IGF-1 for your age and sex is the usual sign of good control. Pasireotide affects blood sugar more, so glucose checks are closer with it.
Treating Neuroendocrine Tumors
Neuroendocrine tumors (NETs) grow from hormone-making cells, most often in the gut or pancreas, and some release hormones that cause flushing or diarrhea. Those symptoms come from hormones such as serotonin entering the blood, rather than from the tumor’s size. Across 15 studies, long-acting octreotide relieved symptoms in about 74% and lanreotide in about 68% of patients.33PubMed. Somatostatin analogues in the treatment of gastroenteropancreatic neuroendocrine (carcinoid) tumours Lowered tumor-hormone levels in blood happened in about half on octreotide and about 4 in 10 on lanreotide.34PubMed. Somatostatin analogues in the treatment of gastroenteropancreatic neuroendocrine (carcinoid) tumours
By lowering hormone release from tumor cells, somatostatin-like drugs ease symptoms even when the tumor remains. Symptoms can return if a dose wears off before the next injection, which is worth telling the care team.
Octreotide was first meant only for symptoms, but it also slows growth, lengthening the time before midgut NETs progress.35PubMed Central. The expanding role of somatostatin analogs in the management of neuroendocrine tumors The anti-tumor effect is mostly stabilization, keeping tumors from growing rather than shrinking them.36PubMed Central. Somatostatin Analogs Therapy in Gastroenteropancreatic Neuroendocrine Tumors: Current Aspects and New Perspectives So “stable disease” on your scan report is often the hoped-for result. Real shrinkage is uncommon with these drugs alone.
Useful questions before starting: Does my tumor show somatostatin receptors on a scan? Is the aim symptom relief, growth control, or both? How will we check whether it’s working, and when?
Somatostatin Scans and Radiation Treatment
DOTATATE is a somatostatin-like molecule that, tagged with a small radioactive tracer called gallium-68, shows where somatostatin receptors are across the whole body on a PET/CT scan.37PubMed Central. Normal Variants, Pitfalls and Artifacts in Ga-68 DOTATATE PET/CT Imaging It is now the standard way to find and stage well-differentiated, slower-growing NETs.38PubMed. Somatostatin receptor imaging with 68Ga DOTATATE PET/CT: clinical utility, normal patterns, pearls, and pitfalls in interpretation A scan showing strong uptake suggests your tumor carries the receptors these drugs need.
On the day, the tracer is injected into a vein, and imaging follows after a short wait. Normal organs like the spleen and kidneys light up too, which isn’t cancer. Doctors may time your long-acting injection around the scan.
PRRT, a radiation-carrying treatment, uses the related molecule Lutetium-177 DOTATATE for NETs that can’t be removed or have spread and carry SSTR2.39PubMed. Overcoming nephrotoxicity in peptide receptor radionuclide therapy using [(177)Lu]Lu-DOTA-TATE for the treatment of neuroendocrine tumours The molecule binds SSTR2, the receptor most common on NETs, up to nine times more strongly than the octreotide version.40PubMed Central. Peptide Receptor Radionuclide Therapy with Lu-177 Octreotate in patients with Somatostatin Receptor Expressing Neuroendocrine Tumors: Six Years Assessment Radiation is delivered mainly to tumor cells, killing them as it decays.41PubMed. Overcoming nephrotoxicity in peptide receptor radionuclide therapy using [(177)Lu]Lu-DOTA-TATE for the treatment of neuroendocrine tumours The kidneys can receive some of the dose, so protecting them is part of planning.42PubMed. Overcoming nephrotoxicity in peptide receptor radionuclide therapy using [(177)Lu]Lu-DOTA-TATE for the treatment of neuroendocrine tumours A tumor with weak uptake may be a poor candidate.
Treatment is given as several infusions spaced weeks apart, usually with a protective amino-acid drip for the kidneys. Blood counts and kidney tests are checked during the course.
Use in Bleeding From Swollen Esophagus Veins
In advanced liver disease, scarred tissue resists blood flow, so blood coming from the gut backs up in the portal vein that leads into the liver. It finds detours through smaller veins, including those lining the lower esophagus, which were not built for that load. These veins stretch and thin, making them fragile and prone to sudden heavy bleeding.
Somatostatin and octreotide seem to work mainly by narrowing the blood vessels supplying the gut.43PubMed. Somatostatin in acute bleeding oesophageal varices. Pharmacology and rationale for use In people with a liver shunt, octreotide lowered portal vein pressure by about 8 to 11% and reduced blood flow.44PubMed. Effects of different octreotide dosages on splanchnic hemodynamics and glucagon in patients with TIPS
In hospital, octreotide is given by drip, usually for a few days, alongside an endoscopy to band or treat the bleeding veins. It supports the procedure that seals the vein but doesn’t replace it.
Can Your Somatostatin Level Be Tested
Measuring somatostatin in blood is technically difficult, which is why little is known about its normal levels in people.45PubMed. Development and validation of a specific radioimmunoassay for somatostatin in human plasma Blood itself interferes with the test, cutting accuracy by about 20% in one lab method.46PubMed. Development and validation of a specific radioimmunoassay for somatostatin in human plasma Different forms and fragments circulate too, and because the hormone mostly acts on neighboring cells, the blood amount is only a small, indirect reflection of what organs are doing. So doctors rely on growth hormone, IGF-1, tumor markers and receptor scans instead.
A rare pancreatic tumor called a somatostatinoma can overproduce the hormone. It can cause diabetes, gallstones and fatty stools, matching the hormone’s braking effects. Specialized testing plus scans and biopsy confirm the diagnosis.
Somatostatin and the Aging Brain
In the brain’s outer layer and memory center, somatostatin-making nerve cells act as quieting cells that keep circuits from overfiring.47PubMed Central. Somatostatin: Linking Cognition and Alzheimer Disease to Therapeutic Targeting Somatostatin reduces release of an excitatory messenger and slows neighboring nerve firing.48PubMed Central. Somatostatin: Linking Cognition and Alzheimer Disease to Therapeutic Targeting
Brain somatostatin falls with normal aging, but the loss is faster in Alzheimer’s.49PubMed Central. Somatostatin: Linking Cognition and Alzheimer Disease to Therapeutic Targeting In Alzheimer’s brains, these cells were reduced by about 30% in one region and over 70% in another.50PubMed Central. Somatostatin: Linking Cognition and Alzheimer Disease to Therapeutic Targeting The cells sit near amyloid plaques, which may lead to their death.51PubMed. Somatostatin and the pathophysiology of Alzheimer’s disease Losing them may contribute to memory decline.52PubMed. Histological characterization of interneurons in Alzheimer’s disease reveals a loss of somatostatin interneurons in the temporal cortex
There is no somatostatin test or drug for Alzheimer’s yet, and the somatostatin-like drugs used for tumors don’t reach the brain in a way known to affect memory. It remains an active research area for future treatments.