Endocrine Metabolic Crosstalk of Insect Growth Regulators: Mechanisms, Resistance, and Climate-Adaptive Pest Management

Insect growth regulators (IGRs), including chitin synthesis inhibitors (CSIs), juvenile hormone analogues (JHAs), and ecdysteroid agonists, have become important components of sustainable pest management because they can selectively disrupt insect-specific developmental, endocrine, or structural processes that differ from those in vertebrates. Rather than treating all IGR classes as operating through one common pathway, this review proposes an integrative framework in which class-specific primary modes of action interact with endocrine regulation, metabolism, stress responses, and ecological context. Across the literature, IGR exposure is associated with changes in carbohydrate, lipid, and protein metabolism, altered detoxification and digestive enzyme activities, and changes in reproductive physiology that can reduce insect fitness. However, these metabolic responses vary substantially with compound class, species, developmental stage, dose, and exposure duration. Their occurrence does not by itself establish active resource reallocation, a common metabolic crisis, or a causal role in mortality. Endocrine–metabolic crosstalk is therefore considered here as a mechanistic framework and testable hypothesis rather than an established universal mechanism of IGR toxicity or resistance evolution. Field-evolved resistance to IGRs is mechanistically diverse and can involve target-site changes, altered detoxification, reduced penetration, transport processes, and regulatory mechanisms, with the strength of evidence varying among compounds and pest species from functionally supported mechanisms to candidate pathways. The review also evaluates integration of IGRs with conventional insecticides and biological control agents and examines how climate warming may alter pest phenology, developmental timing, and temperature-dependent IGR performance, while acknowledging that direct empirical evidence linking climate warming specifically to IGR endocrine or metabolic sensitivity remains limited. Future progress will require stronger functional validation of proposed endocrine–metabolic links, climate-informed deployment strategies, and resistance management based on validated mechanisms and multiple control tactics.