Biology & endocrinology
Hormones, micronutrients, metabolic axes. Continuous assays, not vibes.
Testosterone
Androgen produced by the HPG axis. Basal levels and acute contest reactivity are not the same construct.
Cortisol
Glucocorticoid of the HPA axis. Marks threat, metabolic load, and social evaluation stress.
Testosterone / cortisol ratio
Composite used as a proxy for dual-hormone status. A ratio is not a mechanism.
25-hydroxyvitamin D
Circulating vitamin D status. Strongly confounded by time outdoors, latitude, adiposity, and wealth.
DHEA-S
Adrenal androgen often bundled into 'optimization' panels. Causal behavioral evidence is thin.
Estradiol
Primary estrogen. Relevant to cycle-phase behavior research and to aromatization from testosterone.
Ferritin
Iron store. Deficiency impairs cognition and work capacity; excess is not a performance upgrade.
Insulin resistance (HOMA-IR)
Metabolic inflexibility proxy. Crosses into mood, energy, and long-run health costs.
Oxytocin
Neuropeptide sold as the trust hormone. The registered replication of the 2005 Nature RCT did not find the main effect.