SinS 2025: Forensic quantification of insulin and incretin therapies enhanced by targeted mass spectrometry

Dr Lewis Couchman of Analytical Services International (ASI), based at St George’s University Hospitals NHS Foundation Trust, in London presented new advances in the forensic and clinical quantification of insulin and incretin-based therapies using mass spectrometry. His presentation at the SinS 2025 conference, in Brighton, reviewed methodological progress in measuring endogenous and synthetic insulin, as well as GLP-1 and GIP receptor agonists, which are increasingly used in the management of type 2 diabetes and obesity.

Although insulin has been in therapeutic use for more than a century, Dr Couchman emphasised that its quantification remains analytically challenging. Factors such as rapid degradation in whole blood, the action of proteases and poor specificity in immunoassays have long complicated the detection of both native insulin and its analogues. These problems are particularly acute in forensic toxicology, where robust analytical reliability is essential for identifying cases of insulin misuse, including accidental overdose and criminal poisoning, particularly when sampling from residual blood in the post-mortem setting.

To overcome the limitations of immunoassays and immunoaffinity enrichment, ASI developed an antibody-free workflow based on microelution solid-phase extraction (SPE) and bottom-up liquid chromatography–tandem mass spectrometry (LC–MS/MS). This method digests insulin into distinctive peptide fragments, allowing simultaneous quantification of insulin, C-peptide and glycated peptides. The approach offers enhanced specificity and can distinguish between structurally similar insulin analogues, including lispro, glargine, porcine, bovine and human formulations, even in mixed-treatment scenarios such as post-transplant care.

Dr Couchman also described the development of novel LC–MS/MS methods for detecting GLP-1 and GIP receptor agonists, which are characterised by relatively high in vivo stability and enzymatic resistance, particularly to dipeptidyl peptidase-4 (DPP-4). Although now widely prescribed, still little is known about the pharmacokinetics of these incretin mimetics in forensic contexts. The ASI method, which also employs microelution SPE and triple quadrupole mass spectrometry, enables sensitive detection from low-volume samples and would therefore be well suited for implementation into routine forensic workflows.

The team’s preliminary data indicates that establishing reference concentrations for GLP-1 receptor agonists is essential for both clinical interpretation and medicolegal investigations, especially in cases involving polypharmacy or unexplained weight loss. As millions of individuals are now exposed to these agents, Couchman argued that their measurement should become standard practice both during life in a healthcare setting and at any post-mortem investigation.

In closing, Dr Couchman affirmed ASI’s commitment to improving analytical approaches for hormone and peptide drug quantification, with particular emphasis on forensic application. The group is actively seeking collaborative partners to extend these methods to broader clinical and postmortem investigations.