IGF1 and cancer: Therefore, high-quality individuals (e.g., good health or nutritional status) may afford to bear the costs of elevated IGF-1 levels (e.g. in terms of oxidative damage, accelerated ageing or increased risk of cancer (Shanmugalingam et al. 2016; Montoya et al. 2022b; Nelson et al. 2023)) while benefiting from its fitness-enhancing effects (e.g. boosting fecundity or anti-inflammatory responses) (Higashi et al. 2010) as expected for wild species exposed to forces of natural selection.