Ghrelin

Ghrelin measurement is a specialized laboratory procedure that requires careful sample collection and handling due to the hormone's unique characteristics and rapid degradation in blood samples. Currently, ghrelin testing is primarily used in research settings rather than routine clinical practice, though it's becoming increasingly available for specialized metabolic assessments.

The testing process involves measuring two distinct forms of ghrelin in blood samples. Total ghrelin includes both the active (acylated) and inactive (des-acyl) forms of the hormone, while acylated ghrelin specifically measures only the biologically active form that can bind to receptors and stimulate appetite [4]. The octanoyl modification that makes ghrelin active is rapidly hydrolyzed in blood samples, making proper collection and preservation critical for accurate results [4].

Specialized collection procedures are essential for reliable ghrelin measurements. Patients must fast for 10-12 hours prior to blood collection to establish accurate baseline levels [4]. The blood sample requires collection in special preservative tubes containing protease inhibitors and acidifying agents to prevent ghrelin degradation. Samples must be processed in a refrigerated centrifuge as soon as possible after collection, then immediately frozen at -20°C for preservation [4].

Laboratory analysis typically employs enzyme-linked immunosorbent assay (ELISA) or radioimmunoassay techniques to measure ghrelin concentrations [4]. These methods can detect ghrelin levels in picograms per milliliter (pg/mL), allowing for precise measurement of this hormone even at very low concentrations.

Patient preparation extends beyond fasting requirements. Individuals should avoid medications or supplements that may influence related hormones including cholecystokinin (CCK), glucose, growth hormone, insulin, and somatostatin for at least 48 hours prior to collection when possible [4]. This comprehensive preparation helps ensure that measured ghrelin levels accurately reflect the patient's true hormonal status rather than temporary fluctuations caused by interfering substances.

The complexity of ghrelin measurement and the need for specialized handling explain why this testing isn't yet part of routine health screenings. However, as research continues to demonstrate ghrelin's importance in metabolic health, more standardized testing protocols may become available for clinical use.