Most people find out they have low testosterone, get prescribed a hormone, and never hear about the system that actually makes it. Testosterone is the end product of a longer biochemical cascade that starts well upstream, and every step along the way can go wrong independently. Think of it like fixing a leak downstream without ever checking the pipes.
It All Starts with Cholesterol
Cholesterol is the raw material for every steroid hormone the body produces. Not just testosterone. Estrogen, progesterone, cortisol, DHEA. All of them begin as cholesterol molecules converted inside the mitochondria of cells, primarily in the adrenal glands and gonads.
The first conversion step is the big one. An enzyme called CYP11A1 converts cholesterol into pregnenolone, sometimes called the "mother hormone." This is the rate-limiting step of the entire pathway. Everything downstream depends on it.
This is why aggressive cholesterol-lowering strategies deserve a second look in the context of hormone health. Cholesterol levels below 150 mg/dL have been associated with lower testosterone in observational studies. The point is not that statins are bad. The point is that nobody should be driving cholesterol into the ground without also monitoring what is happening to their hormones.
Pregnenolone: The First Fork in the Road
Once cholesterol converts to pregnenolone, the pathway splits into two competing branches.
Branch one goes through 17-hydroxypregnenolone to DHEA, which eventually becomes testosterone and estrogen. This is the androgenic pathway.
Branch two goes through progesterone toward cortisol and aldosterone. This handles stress response, blood pressure, and immune function.
Both branches compete for the same starting material. The body has to allocate pregnenolone between them, and that allocation is not always balanced.
This brings up the concept of "pregnenolone steal", popular in functional medicine circles. The theory: chronic stress drives constant cortisol demand, which "steals" pregnenolone away from the testosterone branch.
The honest assessment: useful mental model, but the science is more complicated. The adrenal glands and gonads have somewhat independent pregnenolone pools. However, chronic HPA axis activation does suppress gonadal function through other mechanisms, primarily by reducing GnRH pulsatility from the hypothalamus. The end result looks similar to what "pregnenolone steal" predicts, even if the mechanism is different.
Practical takeaway: chronic stress genuinely suppresses testosterone production, and the effect operates upstream of the testes themselves.
DHEA and What It Actually Does
Dehydroepiandrosterone (DHEA) is the most abundant circulating steroid hormone in the human body. DHEA and its sulfated form DHEA-S serve as a reservoir that tissues can convert locally into testosterone and estrogen as needed.
DHEA production peaks in the mid-20s and declines steadily after. By age 70, circulating DHEA-S levels are typically 70-80% lower than their peak. This decline tracks closely with the age-related drop in testosterone. Less precursor means less end product.
For men, DHEA supplementation has shown modest but real effects in studies. Men with genuinely low DHEA-S levels (below 150 mcg/dL) who supplement often see improvements in well-being and energy, sometimes small bumps in testosterone. The effects are not dramatic when levels are already normal.
For women, the picture is arguably more significant. Women produce a larger proportion of their total androgens from adrenal DHEA conversion rather than direct gonadal production. Some studies show meaningful improvements in libido, mood, and bone density in postmenopausal women supplementing DHEA at 25-50mg daily.
Realistic expectations: DHEA is not a testosterone replacement. It is a precursor support strategy that matters most when levels are actually low. Testing DHEA-S before supplementing is the responsible approach. Blindly taking 100mg because a forum post said to is how people end up with acne and hormonal imbalance.
Progesterone Is Not Just a Women's Hormone
Most people hear progesterone and immediately think pregnancy. That association is so strong that many men and their doctors never consider testing it in males. This is a blind spot.
Men produce progesterone in smaller quantities, primarily in the adrenal glands and testes. It serves functions that have nothing to do with reproduction.
As a neurosteroid, progesterone and its metabolite allopregnanolone act on GABA receptors in the brain (the same system targeted by anti-anxiety medications). Adequate levels support sleep quality and reduce anxiety. Men on TRT who complain of insomnia or increased anxiety despite good testosterone levels sometimes have progesterone that has dropped because their own gonadal production has been suppressed.
As an estrogen counterbalance, progesterone opposes some of estrogen's proliferative effects. In the context of TRT, where aromatization can increase estrogen, having adequate progesterone provides a natural balancing mechanism.
Some TRT clinics include low-dose progesterone (100-200mg oral or topical) as part of comprehensive protocols for both men and women. The evidence base for men specifically is still developing, but the physiological rationale is sound and clinical reports are consistently positive.
Why This Matters for TRT
Here is the practical problem most TRT conversations completely ignore.
When someone starts exogenous testosterone, the hypothalamus shuts down its own signaling cascade. LH and FSH drop to near zero. The testes stop producing testosterone on their own. This is expected. What gets less attention is that this shutdown also reduces the body's production of everything upstream. The testes are not just testosterone factories. They also produce pregnenolone, DHEA, and progesterone locally.
This is why some people on TRT report feeling "flat" despite good testosterone numbers. Their testosterone is fine because it comes from a syringe. But their pregnenolone, DHEA, and progesterone may have dropped because nothing is stimulating the body's own steroid production anymore.
The clinics that understand this prescribe comprehensive hormone support rather than just testosterone. The protocol might include testosterone plus pregnenolone (50-100mg daily), DHEA (25-50mg daily), and sometimes progesterone. Defy Medical is known for this approach, offering both DHEA and pregnenolone as part of their protocols. Marek Health similarly includes pregnenolone and takes a deep-dive approach to labs. Royal Medical Center offers pregnenolone and progesterone options at a more accessible price point. And Maximus takes a different route entirely, using enclomiphene and pregnenolone to boost natural production without shutting down the pathway in the first place.
What to Test Beyond Testosterone
The standard TRT blood panel covers total testosterone, free testosterone, estradiol, CBC, and metabolic markers. If the upstream pathway matters (and it does), testing should reflect that.
Pregnenolone (serum): Establishes whether the top of the cascade is healthy. Low pregnenolone with low testosterone suggests the problem may start at the conversion from cholesterol. Functional ranges tend to cluster around 50-100 ng/dL for feeling well.
DHEA-S (serum): The sulfated form is more stable and gives a better picture than DHEA itself. For men under 50, levels below 200 mcg/dL warrant attention.
Progesterone (serum): Rarely tested in men, but worth establishing a baseline for those on TRT with sleep or anxiety complaints.
Cortisol (AM serum or 4-point salivary): A four-point salivary cortisol test throughout the day provides a much better picture of stress physiology than a single morning draw.
When talking to a provider, asking "can we check pregnenolone and DHEA-S alongside the standard panel?" is more productive than walking in with a printed steroidogenesis chart.
The Bigger Picture
Stress, sleep, diet, and metabolic health directly influence where pregnenolone gets allocated and how efficiently the entire pathway operates.
Chronic stress elevates ACTH and drives cortisol production. Persistent HPA axis activation suppresses GnRH and LH secretion at the brain level. Studies on sleep-deprived young men show testosterone drops of 10-15% after just one week of restricted sleep.
Insulin resistance impairs steroidogenesis at multiple points: reduces SHBG, impairs gonadal function, and promotes excessive aromatization of testosterone to estrogen in adipose tissue.
Nutrient status matters at specific enzymatic steps. Zinc is a cofactor for the conversion of androstenedione to testosterone. Magnesium supports testosterone availability. Vitamin D influences testicular function directly.
None of this means lifestyle changes replace TRT for someone with genuine hypogonadism. But for those already on TRT who want to optimize how the whole system functions, addressing these upstream factors is the difference between a protocol that works and one that works well.
Our clinic directory features providers who look beyond a single number and treat the system rather than the symptom.