Steroid hormones produced primarily in gonads (ovaries, testes) and adrenal glands, including estrogens (estradiol, estrone, estriol), androgens (testosterone, DHEA, androstenedione), and progestogens (progesterone). Sex hormones exert profound effects on brain structure, immune function, metabolism, and neuroprotection beyond their reproductive roles.
Sex hormones are synthesized from cholesterol via the steroidogenic pathway: cholesterol → pregnenolone → progesterone → androgens (testosterone) → estrogens (via aromatase). They act through: (1) Nuclear hormone receptors (ER-α, ER-β, PR, AR) that function as transcription factors regulating gene expression, (2) Membrane receptors enabling rapid non-genomic effects (GPER, mER), (3) Conversion to neurosteroids (allopregnanolone from progesterone) modulating GABA and NMDA receptors. Estradiol is neuroprotective (increases BDNF, promotes synaptic plasticity, reduces oxidative stress), anti-inflammatory (inhibits NFκB), and metabolically protective (maintains insulin sensitivity). Testosterone supports muscle mass, bone density, cognitive function, and motivation. Progesterone modulates immune function (shifts toward Th2 during luteal phase) and has GABAergic calming effects.
Declining sex hormones with age (menopause, andropause) increase risk for Alzheimer's disease, cardiovascular disease, osteoporosis, depression, and metabolic syndrome. However, cPNI emphasizes biological amplification—using lifestyle interventions (resistance training, adequate sleep, stress management, specific nutrients) to upregulate endogenous hormone production and receptor sensitivity—rather than exogenous hormone replacement (which carries cancer risks). Sexual activity itself is a biological amplifier, increasing progesterone and IgA without affecting estradiol, demonstrating selective pathway activation.
- Include estrogens (estradiol, estrone, estriol), androgens (testosterone, DHEA), progestogens (progesterone)
- Synthesized from cholesterol via steroidogenic pathway in gonads and adrenals
- Estradiol is neuroprotective, increases BDNF, promotes synaptic plasticity
- Declining sex hormones increase Alzheimer's disease risk (Barron & Pike, 2012)
- Sexual activity selectively increases progesterone and IgA without changing estradiol
- Resistance training upregulates testosterone and growth hormone
- Progesterone converts to allopregnanolone (GABAergic neurosteroid)
- Estrogen has anti-inflammatory effects via NFκB inhibition
- Testosterone supports muscle mass, bone density, motivation, libido
- Biological amplification preferred over exogenous hormone replacement in cPNI
- estradiol — primary estrogen with neuroprotective and metabolic effects
- testosterone — primary androgen supporting muscle, bone, cognition
- progesterone — progestogen that modulates immune function and converts to neurosteroids
- Alzheimer's disease — risk increased by declining sex hormones with age
- biological amplification — cPNI strategy to upregulate endogenous sex hormone production
- sexual activity — biological amplifier that selectively increases progesterone and IgA
- BDNF — neurotrophic factor upregulated by estradiol
- aromatase — enzyme converting testosterone to estradiol
- allopregnanolone — GABAergic neurosteroid derived from progesterone
- resistance training — lifestyle intervention that upregulates sex hormone production
- menopause — natural decline in ovarian estrogen and progesterone production
- insulin resistance — worsened by declining estrogen's metabolic protection
- neuroplasticity — supported by estradiol's effects on synaptic plasticity
- immune system — modulated by sex hormones (Th1/Th2 balance, IgA production)
- NFκB — inflammatory transcription factor inhibited by estrogen
- cholesterol — precursor molecule for all steroid hormone synthesis
- DHEA — adrenal androgen that declines with age
- osteoporosis — accelerated by declining estrogen and testosterone
- depression — associated with low testosterone in men and hormonal fluctuations in women
- HPA axis — shares precursors with sex hormone synthesis; stress depletes sex hormones