Everyone’s talking about hormones these days: testosterone, estrogen, cortisol, thyroid hormone, insulin. We measure them, try to manipulate them, supplement them, replace them. Yes, they are absolutely powerful, but hormones don’t actually lead the system.
The following article is from Dr Deanna Minich and follows on well from the previous blog, explaining how all endocrine signalling is linked to day-night cycles.
Before a hormone is released, before a receptor responds, before metabolism shifts, the body is orienting itself in time. And the strongest signal it uses to do that is light, followed by adequate darkness (and most everyone seems to have a “darkness deficiency” these days!).
This applies to women and men alike.
Keep in mind that hormones are not just chemical communicators. They are signals that align to the rhythm of our lives. They rise and fall in relationship to day and night, light and dark. When those light signals become inconsistent, hormonal communication loses clarity long before anything looks “abnormal” on a lab report. This is why so many people feel off, wired, tired, inflamed, or metabolically stuck even when their hormone numbers appear normal. The issue is often not deficiency in a silo.
The bottom line: the endocrine circuit is losing its delicate balance because light and dark cycles are out of rhythm.
Light is the master regulator of the endocrine system. Morning light anchors cortisol and daytime energy. Darkness at night allows melatonin to rise. These two hormones quietly coordinate almost everything downstream: insulin sensitivity, thyroid signaling, reproductive hormones, immune function, and cellular repair.
In women, circadian disruption can make everything worse, including cycle irregularity, perimenopausal symptoms, and metabolic shifts. In men, it can flatten testosterone rhythms, impair recovery, disrupt sleep quality, and erode metabolic resilience. Different expressions. Same root cause.
I know you’ve heard me talk about the rainbow of foods and I want you to think about the rainbow of light (sunlight). Sunlight is the original full-spectrum signal. It delivers a richness and intensity that artificial lighting can’t fully replicate. When we get outside early in the day, even briefly, we send a powerful message to the nervous system: this is morning. In darker seasons, early schedules, or limited outdoor access, full-spectrum light devices can help reinforce that signal when used in the morning or earlier part of the day. Where we get into trouble is using full-spectrum light without respecting timing.
After sunset, the brain is no longer asking for brightness or spectral richness. It is asking for dimness and warmth. Full-spectrum light at night, even when it looks natural or healthy, contains wavelengths that suppress melatonin and delay biological night. Over time, it blurs the boundary between day and night, and the endocrine system loses its rhythm.
The body depends on contrast: the bright days and the dim evenings. When that contrast erodes, hormonal signaling becomes noisy instead of precise.
Here’s where melatonin comes in…
Melatonin is often misunderstood as just a sleep hormone. It is not. It is a master timing signal involved in hormone recycling, mitochondrial repair, immune balance, glucose regulation, and cellular aging. When melatonin is chronically suppressed by light at night, these systems pay the price, regardless of sex.
This is why hormone protocols and supplements can feel underwhelming when circadian signals are ignored. You cannot optimize hormones in a body that doesn’t know what time it is.
Before asking what hormone to test or take, I always come back to light.
- Are you getting real light early in the day?
- Are you protecting darkness at night?
- Is there a clear separation between your days and evenings?
When people restore these signals, shifts often happen before anything else changes.
Hormones respond when timing is restored.
Get your light right first.
Your hormones will often follow…