Endocrine regulators

Growth hormone (GH) is a vital peptide hormone produced by the anterior pituitary gland. During childhood and adolescence, GH plays a crucial role in stimulating the growth and development of bones, muscles, and internal organs as well as regulating various metabolic processes. In adulthood, GH contributes to maintaining body composition, muscle mass, and overall tissue repair.

GH exerts its effects mainly by stimulating the liver to produce insulin-like growth factor I (IGF-I), which acts on target tissues to promote growth. In the blood, IGF-I is largely bound to insulin-like growth factor-binding protein 3 (IGFBP-3). The levels of GH, IGF-I and IGFBP-3 are tightly regulated by a feedback loop.

GH disorders

GH deficiency arises primarily from hypopituitarism, which may result from genetic mutations, trauma, tumours, or other injuries affecting the pituitary gland. In children, severe GH deficiency leads to significant growth retardation, but this can often be effectively treated with recombinant GH therapy, promoting normal development. Mild deficiencies may remain unnoticed until puberty, when growth spurts fail to occur. In adults, GH deficiency can lead to mental health conditions, fatigue, bone weakness, reduced muscle mass, fat maldistribution and cardiovascular disease.

Excess GH is commonly caused by pituitary adenoma and results in elevated levels of both GH and IGF-I. Hypersecretion of GH in childhood leads to gigantism, while in adults it causes acromegaly, with enlargement of the nose, chin, fingers and toes. Early diagnosis and prompt therapy of acromegaly is crucial, as the excessive hormone levels can cause progressive systemic complications, including cardiovascular, metabolic, respiratory, endocrine and bone disorders.

Biomarker analysis

Measurement of biomarkers plays a crucial role in supporting diagnosis of growth disorders and monitoring the effectiveness of treatment. GH levels naturally fluctuate throughout the day and the hormone has a short half-life of approximately 20 minutes, making single random measurements unreliable for diagnostics. Therefore, GH levels are typically assessed through stimulation or suppression tests to accurately detect deficiency or excess. In contrast, serum concentrations of IGF-I and IGFBP-3 remain relatively stable throughout the day, making them suitable markers to assess GH abnormalities. Their primary clinical use, however, lies in the indirect evaluation of GH therapy effectiveness over time.

Standardised laboratory analysis

Euroimmun and Immunodiagnostics Systems (both part of Revvity) offer fully automated chemiluminescence immunoassays (ChLIA) for the precise quantitative measurement of human growth hormone (hGH), IGF-I, and IGFBP-3. These assays are calibrated against international WHO standards, ensuring accuracy and consistency.

The unique specificity of the IDS hGH assay allows for monitoring of endogenous GH levels in acromegalic patients on pegvisomant therapy. This assay is also suitable for assessing pregnant individuals, as it does not cross react with placental GH. The IGF-I and IGFBP-3 assays are supported by the largest published reference interval studies for both children and adults, conducted as part of a multicentre collaboration across the US, Canada and Europe.

Streamlined workflows

Requiring only small sample volumes, IDS ChLIAs run on fully automated, random-access platforms, which provide rapid turnaround times and streamlined processing with minimal manual intervention. The ChLIAs for growth disorders can be processed simultaneously with assays for other diagnostic indications, enabling flexible and scalable laboratory workflows.

References available at www.euroimmunblog.com/high-quality-diagnostics-growth-disorders-acromegaly/

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