How it fits together · lesson 10 of 11
Hormone & steroidogenesis pathways
Cholesterol → steroid hormones, the HPA and HPG axes, cofactors, and how stress, sleep, and nutrition modulate them.
7 min read · reviewed October 2026
Some of your most powerful hormones — cortisol, testosterone, estrogen, aldosterone — all start from the same humble molecule: cholesterol. Yes, the one with the scary reputation. Your body uses cholesterol as the raw block from which it carves out the steroid hormones, on branching assembly lines called steroidogenesis.
And these lines don't run in isolation. They're commanded from the brain by feedback loops called axes, and they're sensitive to how you sleep, how stressed you are, and what you eat.
One raw material, many hormones
Cholesterol is the single starting block for every steroid hormone. From there, a series of enzymes (running on cofactors like vitamin C, NADPH, and iron-containing P450 enzymes) progressively sculpt it into one hormone or another, depending on the tissue and the signals it's receiving. Block or starve a step and the whole downstream branch is affected — the classic pathway logic, now in the endocrine system.
The steroidogenesis tree — from cholesterol outward
Every steroid hormone is built from cholesterol. It's first converted to pregnenolone — the common ancestor of the entire steroid family. This is the gateway step, run by a P450 enzyme in the mitochondria.
Leads to cortisol — the main stress hormone. It mobilizes energy, modulates immunity, and follows a daily rhythm (high in the morning, low at night). Governed by the HPA axis, the brain-to-adrenal stress loop.
Leads to testosterone and estrogen (and progesterone). These drive reproductive function, bone, muscle, mood, and more. Governed by the HPG axis. Testosterone is also converted to estrogen by the enzyme aromatase.
Leads to aldosterone, which manages sodium, potassium, and blood pressure via the kidneys. Same cholesterol origin, different downstream enzymes.
Steroid synthesis leans on NADPH, vitamin C (concentrated in the adrenal glands), iron-containing P450 enzymes, and adequate cholesterol and dietary fat. Severe energy or fat restriction can blunt sex-hormone output — a real, mechanism-level effect.
The HPA and HPG axes — command and feedback
Your hormone glands don't act alone — the brain runs them like a thermostat. The HPA axis controls stress hormones (cortisol): brain senses stress → tells the adrenal glands to make cortisol → cortisol rises → brain senses that and eases off. The HPG axis controls sex hormones the same way. Because they're thermostats with feedback, chronic stress, poor sleep, and under-eating can reset where the dial sits.
How it works →
Both axes are three-tier feedback loops. HPA: hypothalamus releases CRH → pituitary releases ACTH → adrenal cortex makes cortisol → cortisol feeds back to suppress CRH/ACTH (negative feedback). HPG: hypothalamus releases GnRH (in pulses) → pituitary releases LH/FSH → gonads make testosterone/estrogen → these feed back on the hypothalamus and pituitary. The two axes interact: sustained HPA activation (chronic stress) can suppress GnRH pulsatility, dampening the HPG axis — one mechanistic route by which prolonged stress and severe energy deficit lower sex-hormone output.
What the studies show →
The axis architecture and feedback are textbook endocrinology, not in dispute. Lifestyle effects are well documented at the extremes: chronic sleep restriction lowers testosterone in men; severe energy deficiency and over-training suppress the HPG axis (e.g. functional hypothalamic amenorrhea); chronic stress reshapes cortisol rhythms. Where to be skeptical: most 'hormone-boosting' and 'cortisol-balancing' supplements have weak or inconsistent human evidence, and 'adrenal fatigue' is not a recognized medical diagnosis — true adrenal insufficiency is a specific, testable condition. The reliably effective levers are unglamorous: sleep, adequate (not extreme) energy intake, stress management, and resistance training.
How nutrition and sleep modulate the pathway — without 'boosters'
You can't out-supplement a sleep-deprived, under-fueled, chronically stressed life into great hormones — but the basics genuinely feed the pathway. Steroid hormones need cholesterol and dietary fat as raw material, plus cofactors like vitamin C and iron for the enzymes. Eat too little fat or too few calories for too long and the body, sensing scarcity, dials hormone production down. The fix is adequacy, not megadoses.
How it works →
Steroidogenesis depends on cholesterol delivery, NADPH (reducing power), and a series of cytochrome P450 enzymes (iron-dependent) and hydroxysteroid dehydrogenases; the adrenal glands concentrate vitamin C, used in steroid synthesis. Severe energy deficit and very-low-fat diets reduce substrate and signal scarcity through the HPA/HPG crosstalk described above, lowering sex-hormone output. Sleep is a major regulator — much of daily testosterone production occurs during sleep, so curtailed sleep measurably suppresses it. Resistance training acutely and chronically supports an anabolic hormonal milieu.
What the studies show →
Adequacy effects are well documented: correcting a genuine deficiency (e.g. iron, or severe energy/fat restriction) restores function, and sleep restriction lowers testosterone in controlled studies. What lacks good evidence is the supplement-as-booster framing — most 'testosterone booster' and 'cortisol balancer' products show weak or null human effects beyond correcting an underlying deficiency. Some adaptogens (e.g. ashwagandha) have modest, still-developing evidence for stress/cortisol and certain hormone measures, but they're not a substitute for the foundational levers. Fix sleep, fuel adequately, manage stress, train — then consider targeted repletion of any verified gap.
Why can chronic stress, poor sleep, or severe under-eating lower sex-hormone output?
- They destroy all the body's cholesterol
- They permanently break the enzymes for good
- Sustained HPA-axis activation and energy deficit can suppress the HPG axis's GnRH signaling, dialing down sex-hormone production
- Sex hormones are not made from cholesterol
Show the answer →
C.Sustained HPA-axis activation and energy deficit can suppress the HPG axis's GnRH signaling, dialing down sex-hormone production
The axes are feedback thermostats, and they talk to each other. Chronic stress keeps the HPA axis (cortisol) running hot, and severe energy deficit signals scarcity — both can suppress the pulsatile GnRH signal that drives the HPG axis, lowering testosterone or estrogen. That's why sleep, adequate energy, and stress management are the genuinely effective levers, not 'hormone booster' pills.
Adequate fat, vitamin C, iron status, and overall energy all feed steroidogenesis. Check whether the basics are covered before chasing 'hormone' supplements.