APOE4 and hormones: vitamin D, estradiol, progesterone, testosterone, and thyroid

Hi Phoenix friend,

If you want to watch the full conversation, you can find the video here:

If you would rather get the synthesized value, this post covers the main takeaways.

In this conversation with Dr. Grant Fraser, we continued the APOE4 biomarker series by moving into hormones.

That includes vitamin D, estradiol, progesterone, testosterone, and thyroid.

The recurring theme was the same one that has come up throughout this biomarker series: the target is not "high" or "low."

The target is the right range for the right person at the right time.

Hormones are powerful because they touch sleep, mood, metabolism, vascular function, bone health, mitochondrial function, inflammation, and brain function. But that also means they are not something to optimize casually.

Testing matters. Timing matters. The route of delivery matters. And for some interventions, especially hormone replacement later in life, the risk-benefit picture can change depending on when you start.

Vitamin D: measure the level, do not guess the dose

Vitamin D is called a vitamin, but biologically it behaves more like a hormone.

Dr. Fraser's practical target range was roughly:

Vitamin D: about 40 to 70 ng/mL

He mentioned that some clinicians may prefer narrower versions of that range, such as 40-60 or 50-70, but the general idea is to avoid both deficiency and excess.

One important point: the dose someone takes does not tell you their level.

The USDA recommendation is around 800 IU per day, but Dr. Fraser said many of his patients need closer to 5,000 IU per day to reach a therapeutic blood level. Some need none. Some need much more. That is why serum testing matters.

Vitamin D came up as relevant for:

• Bone health

• Osteoporosis prevention

• Vascular health

• Immune and inflammatory regulation

• Possibly modest brain-health support

He also emphasized the supporting nutrients that often get ignored.

Magnesium matters because vitamin D metabolism depends on magnesium. Vitamin K2, especially MK-7, is often paired with vitamin D for vascular health, with a common dose around 200 mcg in his practice. The theory is that K2 helps support better calcium handling rather than encouraging calcium deposition in blood vessels.

As always, this is a discussion to have with a clinician, especially if using higher-dose vitamin D or if calcium, kidney, parathyroid, vascular, or bone issues are involved.

Estradiol: brain health, timing, and the menopause window

Estradiol was one of the most important parts of the discussion.

Dr. Fraser described estradiol as relevant to multiple brain-health pathways, including:

• Mitochondrial function

• Neuroinflammation

• Cholinergic signaling

• Cerebral blood flow

• Synaptic plasticity

• Glucose metabolism

• Vascular function

For women, the menopause transition creates a major hormonal shift. Dr. Fraser's view is that, unless there is a specific contraindication, hormone replacement therapy can be a very sensible conversation to have before or during the menopause transition.

He emphasized that the process often starts before menopause. In perimenopause, progesterone may decline first, often affecting sleep and mood before estradiol drops fully.

That matters because sleep is not a side issue. If sleep breaks down, the rest of the system tends to suffer.

The timing question: starting HRT early vs. much later

The most nuanced part of the estradiol discussion was timing.

Starting hormone support around perimenopause or menopause is a very different question from starting it 10, 15, or 20 years after menopause.

Dr. Fraser raised the concern that after many years without estradiol, the brain and vascular system may be in a different state. There may be more endothelial dysfunction, less neuroplasticity, more mitochondrial dysfunction, more inflammation, or more vascular disease.

In that context, suddenly adding hormones may not carry the same risk-benefit profile.

This is why he sees later initiation as an individualized decision.

In someone with excellent vascular health, low inflammation, strong cognitive or functional testing, minimal white matter disease, and no obvious vascular burden, he may be more comfortable considering it.

In someone with more vascular disease, inflammation, or signs of significant biological aging, he is more cautious.

The key takeaway is not "everyone should start HRT."

The takeaway is that timing and context matter.

Estradiol route and targets

Dr. Fraser generally favors topical or transdermal estradiol rather than oral estrogen.

Most of his patients use FDA-approved estradiol patches. He mentioned patch doses ranging from 0.025 mg/day to 0.1 mg/day, adjusted based on response and lab monitoring.

His practical estradiol target for women was roughly:

Estradiol: about 40 to 70

Units and assay context matter, so this is not a DIY target. But it gives a sense of the physiological range he is aiming for rather than pushing levels high.

For men, estradiol matters too. Men produce estradiol from testosterone, and very low testosterone can mean low estradiol. Dr. Fraser likes men to have estradiol roughly in the mid-20s. Too low may affect mood and bone health. Too high may contribute to gynecomastia or unwanted fat distribution.

Again: sweet spot, not maximum.

Progesterone: not just a uterus hormone

One of the clearest points in the discussion was Dr. Fraser's view that progesterone is not only relevant for women who still have a uterus.

He strongly pushed back on the idea that progesterone's only role is preventing uterine cancer when estrogen is prescribed.

Progesterone receptors exist in the brain. Progesterone can act through GABA-related pathways and may significantly affect sleep and mood.

For many women in perimenopause or menopause, progesterone can be one of the most meaningful interventions for sleep disturbance.

Dr. Fraser generally uses FDA-approved micronized progesterone.

The practical takeaway: progesterone is part of the brain-health and sleep conversation, not just the uterine-protection conversation.

Testosterone in women: optional, but not irrelevant

Testosterone is often discussed as a male hormone, but women produce and use testosterone too.

Dr. Fraser described testosterone in women as optional but potentially useful, depending on symptoms, levels, and goals.

He referenced Dr. Susan Davis's work in Australia, where there is more formal research and a commercially available testosterone product designed specifically for women.

In his practice, he tends to target a physiological range rather than pushing high levels. He mentioned free testosterone targets around 4-8, depending on assay and context, often staying toward the lower side.

For women, dosing is much lower than in men. He mentioned topical doses around 4-10 mg/day, compared with much higher male dosing.

The goal is not masculinization. The goal is physiologic normalization when appropriate.

Testosterone in men: normalize, don't blast

For men, Dr. Fraser made a sharp distinction between restoring a physiologic level and bodybuilding-style supraphysiologic dosing.

Those are completely different things.

Normalizing low testosterone may help with:

• Mood stability

• Well-being

• Lean body mass

• Bone health

• Insulin sensitivity

• Energy and function

But pushing testosterone far above physiologic levels can create serious metabolic problems. He used the example of bodybuilders using very high testosterone and growth hormone doses, often requiring large amounts of insulin because blood glucose regulation becomes so impaired.

The practical message: low testosterone can matter, but "more" is not the goal.

Free testosterone matters more than total testosterone

One of the most useful testing points was this:

Total testosterone alone can be misleading.

Sex hormone-binding globulin, or SHBG, changes how much testosterone is actually available. Someone can have a high total testosterone and low free testosterone. Someone else can have a low total testosterone and a normal or high free testosterone.

Dr. Fraser was very clear that free testosterone is what he cares about clinically.

If a clinician only checks total testosterone, they may miss the real picture.

Men with low testosterone: find the cause before replacing it

For men, Dr. Fraser does not jump straight to testosterone replacement.

He first wants to know whether the issue is primary testicular failure or whether the brain is not signaling the testicles strongly enough.

In many men, the testicles can still produce testosterone if the signal is improved.

That is why he often considers approaches that stimulate endogenous production, such as hCG or other signaling-based therapies, before direct testosterone replacement.

His concern with direct testosterone is that it can suppress natural production and lead to testicular atrophy. It is also a controlled substance, which can create continuity problems if someone needs ongoing prescribing for decades.

His preference, when possible, is to help the body produce more rather than replace it directly.

Thyroid: the standard lab range may be too loose

The thyroid section was another practical one.

Dr. Fraser's view is that the standard U.S. TSH reference range is too permissive. Many labs do not flag TSH as abnormal until it is above about 4.5.

He prefers a tighter target.

His practical "happy spot" for TSH was:

TSH: about 0.5 to 1.5

He often uses TSH above 2.5 as a trigger to consider whether thyroid support is appropriate, depending on the person.

He generally checks free T3 and free T4 as well, not just TSH.

Thyroid treatment: adjust slowly and monitor

Most people who need thyroid support start with T4, commonly levothyroxine or Synthroid, because it has a long half-life and is stable.

Some people do better with desiccated thyroid preparations like Armour Thyroid or NP Thyroid, which contain both T4 and T3. Others do better on a specific brand rather than generic.

The point is not that one form is always best. The point is that thyroid treatment often requires monitoring, adjustment, and paying attention to how the person actually feels.

Dr. Fraser typically rechecks thyroid labs every 4-6 weeks after a change. Once stable, he may check again at three months and then yearly.

Hashimoto's and symptoms of hypothyroidism

If someone is hypothyroid, Dr. Fraser thinks it is reasonable to check thyroid antibodies at least once, especially thyroid peroxidase antibodies and thyroglobulin antibodies, to see whether Hashimoto's thyroiditis is part of the picture.

Hashimoto's can also contribute to inflammation and may affect CRP.

He also mentioned that clinicians should examine the thyroid for nodules and consider ultrasound when appropriate.

Common hypothyroid signs and symptoms discussed included:

• Low energy

• Slower heart rate

• Sluggish reflexes

• Depression

• Weight gain

• Waxy or thickened skin

• Loss of the outer third of the eyebrows

The eyebrow point is a classic physical finding that many people have never heard of.

The biggest takeaway

Hormones are not separate from brain health.

Vitamin D, estradiol, progesterone, testosterone, and thyroid all touch systems that matter for cognition, vascular health, metabolism, sleep, inflammation, and resilience.

But they need to be handled with care.

The goal is not to chase high numbers.

The goal is not to treat lab ranges casually.

The goal is to restore and maintain physiological function where it makes sense.

For APOE4 carriers, that context may matter even more because the brain may be more vulnerable to inflammation, vascular dysfunction, metabolic stress, and hormonal disruption.

The most useful framework from this conversation is:

Measure the right thing.

Interpret it in context.

Act only when the result changes what you do.

Retest after changes.

Do not confuse "optimal" with "more."

Educational only, not medical advice. Hormones and thyroid treatment should be discussed with a qualified clinician who understands your full medical history, risk profile, and goals.

Cheers,

Kevin

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