Somatostatin
[CAS# 51110-01-1]

Identification

• Classification: API >> Hormone and endocrine-regulating drugs >> Other hormone
• Name: Somatostatin
• Synonyms: Growth hormone release-inhibiting factor
• Protein Sequence: AGCKNFFWKXFXSC
• Molecular Formula: C₇₆H₁₀₄N₁₈O₁₉S₂
• Molecular Weight: 1637.89
• CAS Registry Number: 51110-01-1
• EC Number: 256-969-7
• SMILES: CC(C1C(=O)NC(C(=O)NC(C(=O)NC(C(=O)NC(CSSCC(C(=O)NC(C(=O)NC(C(=O)NC(C(=O)NC(C(=O)NC(C(=O)NC(C(=O)N1)CCCCN)CC2=CNC3=CC=CC=C32)CC4=CC=CC=C4)CC5=CC=CC=C5)CC(=O)N)CCCCN)NC(=O)CNC(=O)C(C)N)C(=O)O)CO)C(C)O)CC6=CC=CC=C6)O

Properties

• Density: 1.4±0.1 g/cm³ Calc.^*
• Boiling point: 1970.9±65.0 ºC 760 mmHg (Calc.)^*
• Flash point: 1145.7±34.3 ºC (Calc.)^*
• Solubility: Soluble 0.30 mg/mL (water) (Expl.)
• Index of refraction: 1.67 (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Discovory and Applicatios

Somatostatin is a naturally occurring peptide hormone that acts as a universal inhibitor of endocrine and exocrine secretions. It is produced in several tissues, including the hypothalamus, pancreas, gastrointestinal tract, and the central nervous system. Somatostatin exists in multiple forms, primarily as a 14-amino acid peptide (somatostatin-14) and a 28-amino acid peptide (somatostatin-28), both of which share a common sequence at the N-terminus.

The discovery of somatostatin occurred in the 1970s, when it was identified as a hypothalamic factor that inhibits the secretion of growth hormone from the anterior pituitary. Subsequent studies revealed its broader physiological roles, including the inhibition of insulin, glucagon, gastrin, and other hormone secretions, as well as suppression of gastrointestinal motility and pancreatic enzyme release. This multifunctional regulatory capacity highlights somatostatin’s role as a central modulator of endocrine and exocrine function.

Somatostatin exerts its effects by binding to specific G protein-coupled receptors, designated as somatostatin receptors (SSTR1–SSTR5). These receptors are differentially expressed in various tissues and mediate distinct biological responses. Activation of somatostatin receptors leads to inhibition of adenylate cyclase activity, reduction of intracellular calcium, and modulation of potassium channels, ultimately decreasing hormone release and cellular excitability. The diverse receptor distribution allows somatostatin to finely regulate endocrine signaling in multiple organ systems.

Pharmacologically, synthetic analogues of somatostatin, such as octreotide and lanreotide, have been developed to mimic the inhibitory actions of the natural hormone while improving stability and half-life in circulation. These analogues are used clinically to treat conditions such as acromegaly, where excess growth hormone secretion occurs, and neuroendocrine tumors that secrete hormones like insulin or gastrin. They are also employed to manage severe gastrointestinal bleeding and certain forms of diarrhea associated with hormone-secreting tumors.

Somatostatin has a very short half-life in circulation, typically ranging from 1 to 3 minutes, due to rapid enzymatic degradation. Its synthetic analogues extend the duration of action to several hours, permitting intermittent or continuous dosing for therapeutic purposes. Administration routes for synthetic analogues include subcutaneous injection, intramuscular depot formulations, and, in some cases, intravenous infusion.

In addition to its endocrine and gastrointestinal effects, somatostatin modulates neuronal activity in the central nervous system, influencing neurotransmission, nociception, and cognitive functions. The peptide’s inhibitory actions on neurotransmitter release contribute to its potential use in managing conditions such as migraine, epilepsy, and certain neurodegenerative disorders.

Overall, somatostatin serves as a critical inhibitory hormone with widespread physiological and pharmacological significance. Its discovery and characterization have provided insights into endocrine regulation and led to the development of clinically valuable analogues that improve the management of hormone-secreting disorders and gastrointestinal pathologies.

References

Brazeau P, Vale W, Burgus R, Ling N, Butcher M, et al. (1973) Hypothalamic polypeptide that inhibits the secretion of immunoreactive pituitary growth hormone. Science 179(4068) 77–79 DOI: 10.1126/science.179.4068.77