Somatostatin

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Endogenous cyclic 14-amino acid inhibitory peptide; the "universal inhibitor" that suppresses GH, insulin, glucagon, gastric acid, and numerous other hormones. Template for octreotide, lanreotide, and pasireotide.

Quick Facts

Property	Value
Also Known As	SST-14, SRIF (somatotropin release-inhibiting factor), somatotropin release-inhibiting hormone (SRIH)
Category	GH Axis / Endogenous reference peptide
Sequence	AGCKNFFWKTFTSC (14 aa; cyclic via Cys3-Cys14 disulfide bond). Also exists as SST-28 (N-terminally extended form)
Molecular Weight	~1638 Da (SST-14); ~3149 Da (SST-28)
Molecular Formula	C₇₆H₁₀₄N₁₈O₁₉S₂
PubChem CID	53481610
Administration	Not used therapeutically (half-life too short); analogs used instead
Typical Dose Range	Not applicable — endogenous reference. IV infusion used only in research
Half-Life	~3 minutes (rapid enzymatic degradation by endopeptidases)
Storage	Research-grade: lyophilized, -20 C
FDA Status	Not a drug product; endogenous hormone. FDA-approved analogs: octreotide (1988), lanreotide (2007), pasireotide (2012)
WADA Status	Not listed (analogs may be relevant for specific doping scenarios)

Mechanism of Action

Somatostatin was first identified in 1973 by Brazeau et al. as a hypothalamic peptide that inhibits GH secretion, but it is now recognized as a broadly distributed inhibitory peptide produced in the hypothalamus, pancreatic delta cells, GI D cells, thyroid C cells, and neurons throughout the CNS (PMID-10433861).

Somatostatin signals through five G-protein coupled receptor subtypes (SSTR1-5), all of which couple to inhibitory G proteins (Gi/Go). The common downstream effects include:

Inhibition of adenylyl cyclase → reduced cAMP → decreased hormone secretion
Activation of potassium channels → membrane hyperpolarization → reduced excitability
Inhibition of voltage-gated calcium channels → reduced calcium influx → decreased vesicular exocytosis
Activation of phosphotyrosine phosphatases → antiproliferative effects

The receptor subtypes show tissue-specific expression (PMID-16625838):

SSTR2: Pituitary (GH/TSH inhibition), GI tract (gastric acid inhibition), neuroendocrine tumors (basis for octreotide, lanreotide, PRRT)
SSTR5: Pancreatic islets (insulin/glucagon inhibition), pituitary (ACTH inhibition — basis for pasireotide in Cushing's)
SSTR1: Brain (widespread), not typically targeted therapeutically
SSTR3: Proapoptotic signaling — potential antitumor relevance
SSTR4: Brain (pain modulation, cognition)

The critical limitation of native somatostatin is its ~3-minute half-life, which makes it impractical for therapeutic use. This drove the development of metabolically stable analogs with selective SSTR subtype profiles.

Key Research Areas

Neuroendocrine regulation — Foundational inhibitor of GH, TSH, ACTH, insulin, glucagon (PMID-10433861)
SSTR subtype pharmacology — Basis for rational drug design of selective analogs (PMID-16625838)
Neuroendocrine tumor biology — SSTR2 expression on NETs enables both imaging (OctreoScan) and therapy (PRRT)
Acromegaly treatment — SSTR2-mediated GH suppression via octreotide and lanreotide
Cushing's disease — SSTR5-mediated ACTH suppression via pasireotide

Evidence Level Summary

Evidence Type	Count	Notes
Human RCTs	N/A	Native somatostatin not used; analogs have extensive RCT data
Systematic reviews	Several	For analog classes (octreotide, lanreotide, pasireotide)
Human observational	Many	Endocrine physiology studies
Animal in vivo	Extensive	Foundational neuroendocrine research
In vitro	Extensive	Receptor cloning, signaling, selectivity

Clinical Applications

Somatostatin itself is not used clinically. Its analogs are used for:

Acromegaly (octreotide, lanreotide, pasireotide)
Neuroendocrine tumors (octreotide, lanreotide, Lu-177-DOTATATE)
Cushing's disease (pasireotide)
Carcinoid syndrome (octreotide)
VIPomas, gastrinomas (octreotide)

Protocols Using This Peptide

Not used in peptide therapy protocols. Referenced as context for somatostatin analog pharmacology.

Ageless Peps Products

Somatostatin is an endogenous hormone and is NOT sold as a product. It is included in this vault as the reference molecule for the somatostatin analog drug class.

Dosing Reference

Research/Clinical Use of Native Somatostatin

Route	Dose Range	Frequency	Duration	Source
IV infusion	250-500 mcg/hr	Continuous infusion	Hours (acute GI bleeding)	Clinical research only

Cycling

Not applicable — native somatostatin is used only as continuous IV infusion in acute settings due to its ~3-minute half-life. The entire rationale for analogs is to achieve sustained receptor activation.

Contraindications & Safety

Contraindications: Not applicable for endogenous hormone
Side effects of exogenous infusion: Rebound hormone hypersecretion after stopping infusion, hyperglycemia (insulin suppression), abdominal discomfort
Drug interactions: Opposes GH secretagogues (ipamorelin, MK-677, sermorelin, tesamorelin)
Pregnancy/nursing: Endogenous hormone; no therapeutic use
Special populations: Somatostatin tone increases with aging (contributing to age-related GH decline)

Synergistic Combinations

Not applicable as a therapeutic agent. Mechanistically:

Somatostatin is the physiological counterpart to GHRH and ghrelin — they form the inhibitory arm of the GH regulatory axis
Understanding somatostatin explains why GH secretagogues produce pulsatile (not continuous) GH release — they work with natural somatostatin withdrawal

Related Research

PMID	Title	Year	Study Type
10433861	Somatostatin and Its Receptor Family	1999	Narrative Review
16625838	Physiology of Somatostatin Receptors	2006	Narrative Review

References

PMID-10433861 — Patel, Somatostatin and its receptor family, Front Neuroendocrinol 1999
PMID-16625838 — Cervia et al., Physiology of somatostatin receptors, Eur J Endocrinol 2006

Educational Note: Somatostatin is an endogenous hormone included in this vault for educational purposes. Understanding somatostatin physiology is essential for comprehending the mechanism and rationale of somatostatin analogs (octreotide, lanreotide, pasireotide) and PRRT (Lu-177-DOTATATE).

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