Research

Hormonal

Growth Hormone (GH) assay choice significantly impacts the interpretation of exercise-induced GH responses, with bioassays detecting much higher concentrations than immunoassays due to the presence of bioactive GH aggregates.

For most exercisers, this is a research note. However, it suggests that standard blood tests for GH may not fully capture the body's anabolic response to exercise. Do not rely on single GH blood draws to judge training effectiveness.

GoodQualifiesHIGH confidence
Plasma GH concentrations measured by this in vivo bioassay were estimated to be much greater (∼300x) than those measured by immunoassay. Further, in 1978 this group reported that a pituitary growth factor, which escaped detection by immunoassay, nevertheless had strong GH activity in the established rat tibia bioassay (95).
William J. Kraemer et al. · Frontiers in Endocrinology · 2020

Why this rating

The paper cites specific historical studies (Ellis et al.) demonstrating the discrepancy between bioassays and immunoassays.

Source

Growth Hormone(s), Testosterone, Insulin-Like Growth Factors, and Cortisol: Roles and Integration for Cellular Development and Growth With Exercise

William J. Kraemer et al. · Frontiers in Endocrinology · 2020

DOI 10.3389/fendo.2020.00033

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DOI resolved against Crossref · corpus check 2026-06-10

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