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Acromegaly
Published in Nadia Barghouthi, Jessica Perini, Endocrine Diseases in Pregnancy and the Postpartum Period, 2021
SRLs include octreotide, lanreotide, and pasireotide. Octreotide and lanreotide are first-generation SRLs that bind with a high affinity to somatostatin receptor (SSTR) 2 subtype. There are multiple octreotide dosage forms, including a rapid-acting octreotide injection, long-acting release (LAR) injection, and a recently FDA-approved delayed-release oral capsule.9,14Lanreotide is a monthly subcutaneous injection.Pasireotide is a second-generation SRL that binds to both SSTR2 and SSTR5. Greater biochemical control has been demonstrated for pasireotide LAR when compared to octreotide LAR. Pasireotide LAR is associated with a higher rate of hyperglycemia and is therefore not an optimal choice for patients with poor glycemic control.13,15For patients on long-acting SRLs, Endocrine Society guidelines recommend transitioning to short-acting octreotide two months before trying to conceive.9 A recent review notes that patients frequently conceive while receiving long-acting SRLs and suggests measuring a human chorionic gonadotropin (hCG) level prior to each injection to minimize fetal exposure.6
Neuroendocrine tumours
Published in Anju Sahdev, Sarah J. Vinnicombe, Husband & Reznek's Imaging in Oncology, 2020
Sairah R Khan, Kathryn L Wallitt, Adil Al-Nahhas, Tara D Barwick
More recently, a novel class of radiolabelled somatostatin receptor analogues have been labelled with the positron emitting radionuclide gallium-68 (68Ga) and 68Ga PET-CT now forms the gold standard of care in terms of functional imaging in NETs. 68Ga is generator produced, eliminating the need for an expensive cyclotron facility. 68Ga has a half-life of 68 minutes and can be attached to biomolecules through chelators such as DOTA. There are several 68Ga-labelled tracers available for clinical use, collectively termed 68Ga-DOTA-peptides. These include 68Ga-DOTATATE, 68Ga-DOTANOC, and 68Ga-DOTATOC. All 68Ga-DOTA-peptides have a higher affinity for SSTR2 than that of 111In-octreotide. 68Ga-DOTANOC is the only ligand that also has a high affinity for SSTR5. Although there are some differences in the affinity profiles of the different 68Ga-DOTA-peptides, comparative studies have shown only minor differences in lesion detection rates (29–31).
Involvement of Dopamine with Various Cancers
Published in Nira Ben-Jonathan, Dopamine, 2020
Interactions between somatostatin and DA receptors are of particular relevance to the diagnosis and treatment of NETs/NECs [107,120]. Both receptors belong to the G-protein-coupled receptor (GPCR) superfamily and share some structural and functional characteristics. Given the high expression of somatostatin receptors (SSTRs) in many NETs, somatostatin analogs have been incorporated into medical therapy for these tumors. Co-expression of SSTR and D2R was examined by immunohistochemistry in GEP neuroendocrine tumors (GEP-NETs) from 46 patients [121]. Overall, 76% of the tumors were positive for different types of SSTRs, whereas 37% were positive for D2R alone. Co-expression of SSTRs and D2R was seen in 88% of tumors. The authors concluded that the high rates of SSTR2A and SSTR2B and lower expression of SSTR5 in these tumors are of great importance for more accurate imaging, staging and targeted therapy of the disease. Moreover, the co-expression of SSTRs and D2R in a significant number of the cases offers a potential therapeutic alternative for GEP-NETs. A similar profile of DA and somatostatin receptor co-expression was reported in another study using quantitative polymerase chain reaction [118].
Drug treatment strategies for secondary diabetes in patients with acromegaly
Published in Expert Opinion on Pharmacotherapy, 2020
Sylvère Störmann, Jochen Schopohl
As surgical removal of the pituitary adenoma in acromegaly is not always successful or a surgical approach is not practicable (either from a technical standpoint or due to patient preference), pharmacological treatment options play an important role in the therapeutic landscape of acromegaly [74]. Somatostatin analogues (SSA) are synthetic somatostatin receptor ligands (SRL) that are structurally similar to somatostatin [86]. Somatostatin is a naturally occurring peptide that binds to several types of receptors (SSTR1 through SSTR5) that are widely distributed to varying extent on cells throughout the body [87]. Neuroendocrine pancreatic cells in particular express different subtypes of SSTR. SSA on the other hand have varying binding affinity to the SSTR subtypes. This explains why the effects of somatostatin and its analogues on glucose homeostasis differ one from another. Since their commercialization in the 1980s, SSA have become the cornerstone of medical acromegaly treatment as reflected by guidelines and consensus statements [74,88,89].
The safety of lanreotide for neuroendocrine tumor
Published in Expert Opinion on Drug Safety, 2019
Amandeep Godara, Nauman S. Siddiqui, Margaret M. Byrne, Muhammad Wasif Saif
Somatostatin is a naturally occurring tetradecapeptide. The isolation of a growth hormone inhibiting polypeptide from sheep hypothalamus in 1973 served as the catalyst in identification and understanding of its action [8]. Later on, somatostatin was also found to be secreted by various other organs, including gastrointestinal (GI) tract, pancreas, and regions of the central nervous system outside the hypothalamus [9]. It has important physiological functions in the GI tract, pancreas and CNS, including modulation of GI and pituitary secretions. Its actions are mediated by a group of five G-protein coupled somatostatin (sst) receptors, sst1-sst5 [10]. Among these receptors, sst2 and sst5 are predominantly expressed in the GI tract [11]. Due to its inhibitory action on GI secretions and motility, it is useful for controlling refractory diarrhea [12]. Similarly, it also has a role in the treatment of symptoms resulting from over secretion of hormones by neuroendocrine tumors, as cell surface somatostatin receptors are present in up to 80–90% of all GEP-NET [5–7]. Somatostatin receptors are also expressed in tumor neovasculature, thus somatostatin may also have a role as an antiangiogenic therapy [13]. Being a cell surface receptor, it also has applicability in neuroendocrine tumor visualization and tumor-targeted therapies [14].
Peptide receptor radionuclide therapy in neuroendocrine neoplasms and related tumors: from fundamentals to personalization and the newer experimental approaches
Published in Expert Review of Precision Medicine and Drug Development, 2023
As discussed previously the somatostatin analogues target SSTR on tumor surfaces. There are 5 subtypes of SSTRs (SSTR1 to SSTR5) present naturally in the body. SSTR-2 receptor-mediated action inhibits hormone release and also causes anti-proliferation, whereas stimulation of SSTR-2 and 3 causes apoptosis, which forms the basis of the use of (non-radio-labeled)octreotideand SSAs in the treatment of NETs. They show proven efficacy in controlling secretory symptoms and inhibiting tumor growth [20,21].