Biology & endocrinology
Hormones, micronutrients, and metabolic axes. Measurable biological markers.
Major cardiovascular events
A first heart attack, stroke, or cardiovascular death. The papers count that composite of events, not a blood-pressure reading.
Cortisol
The main glucocorticoid of the HPA axis. It rises with threat, metabolic load, sleep loss, and social evaluation.
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.
Fertility
The chance of a pregnancy, a live birth, an ovulation, or a usable sperm count. A blood testosterone reading is a different measure.
Hearing loss
A measured drop in how well the ear picks up sound, usually a pure-tone average. Age is a nearby cause, not the same score.
Insulin resistance (HOMA-IR)
How poorly insulin clears glucose, often scored with HOMA-IR from fasting glucose and insulin. It sits between diet, sleep, and long-run metabolic risk.
Kidney disease
A drop in how fast the kidneys filter blood (eGFR), a rise in urine albumin, or a kidney-failure event. A heart attack or stroke is a different count.
Blood lead
Childhood blood lead, measured in µg/dL. Paint, dust, water, and gasoline are how it gets in; the reading is the blood number.
All-cause mortality
Death from any cause. The papers count a recorded death, whatever the certificate names.
Muscle strength
How much force a muscle can produce, or the lean mass that usually travels with it. It is an outcome, not the habit of going to the gym.
Oxytocin
Neuropeptide sold as the trust hormone. The registered replication of the 2005 Nature RCT did not find the main effect.
Prenatal famine exposure
Exposure to famine while still in the womb, dated by the Dutch Hunger Winter of 1944-1945. It is an intrauterine date, not an adult diet.
Obstructive sleep apnea
Airway collapse in sleep that stops or shallows breathing. Hours in bed are a different clock.
Testosterone / cortisol ratio
Composite used as a proxy for dual-hormone status. A ratio is not a mechanism.
Testosterone
Androgen produced by the HPG axis. Basal levels and acute contest reactivity are not the same construct.
25-hydroxyvitamin D
Circulating vitamin D status. Strongly confounded by time outdoors, latitude, adiposity, and wealth.