Chronic fatigue with “no cause”, regular but painful cycles, stubborn anxiety despite a good lifestyle, unexplained abdominal weight gain…
You have almost certainly met patients like this: the hormone work-up comes back “within range”, yet the imbalance is clearly there.
In this kind of picture, the endocrine system becomes an essential line of enquiry.
That is what Dr Christian Boyer explored in a Simplycure webinar, shining a light on the main hormonal axes… and the still too often overlooked role of the gut microbiota in their regulation.
This article pulls together the key takeaways to enrich your care, with a clinical, integrative approach that works in day-to-day practice.
1. What is the endocrine system?
When the tests are normal but “something is off”, going back to the logic of the endocrine system often helps you understand your patient better.
This system rests on a set of interconnected glands that secrete hormones into the circulation, with the job of regulating the body's major functions : metabolism, reproduction, stress, growth, homeostasis…
In consultation, it is mainly the hierarchical axis structure (HPA, thyroid, gonadal…) that deserves revisiting. It helps you grasp the cascade effects, and spot the so-called “functional” imbalances that are often invisible on routine tests.
The overall role of the endocrine system
Maintaining internal homeostasis
Regulating growth and development
Managing stress responses
Controlling energy metabolism
Orchestrating reproduction and fertility
The main glands involved
GlandMain functionHypothalamusNeuroendocrine command centrePituitary (anterior pituitary)Conductor of the peripheral hormonal axesThyroidBasal metabolism, thermoregulation, cognitionAdrenals (cortex and medulla)Stress response, blood glucose, blood pressurePancreas (islets of Langerhans)Blood glucose regulation (insulin, glucagon)Ovaries / TestesSexual function and reproduction
A logic of hierarchical axes
As a reminder, the endocrine system is organised into axes:
The HPA axis (hypothalamic-pituitary-adrenal): stress and cortisol management
The thyroid axis: energy and autonomic regulation
The gonadal axis (ovaries / testes): reproduction, cycles, libido
And it is precisely this organisation that explains why chronic stress can disrupt a menstrual cycle, or why subclinical hypothyroidism can come with marked PMS or a sluggish bowel.
When the central axis wavers, it is often the target tissues that “take the hit” first.
2. Why do some imbalances stay invisible on tests?
A hormone work-up “within range” does not guarantee functional balance. You have no doubt seen it yourself many times: the levels look fine, but the symptoms stay.
Example: A patient with mild functional hypercortisolism may have a work-up within range but typical symptoms (fatigue that does not lift with rest, gut-linked anxiety…). What matters here is not the total cortisol value, but the tissue response and the state of the HPA axis as a whole.
Several variables escape standard assays:
The rhythm of secretion (pulsatility),
The sensitivity of peripheral receptors,
Actual bioavailability (transporters, plasma binding),
Low-grade inflammation or the immune terrain,
Hepatic and intestinal clearance capacity.
This kind of gap between clinical picture and biology is exactly why it is worth cross-referencing tests, symptoms, history and underlying terrain: a “normal” level does not rule out an imbalance, especially if it is compensated or in an adaptation phase.
3. Microbiota and hormonal regulation: clinical markers axis by axis
When the digestive terrain gets involved, some hormonal imbalances read very differently. Recent data confirms it: the gut microbiota acts as a genuine endocrine modulator, able to influence several axes at a distance.
To picture these interactions more easily, here is a clinical summary axis by axis, with the signs to look for, the key mechanisms, and the levers to use in the consulting room.
Hormonal axisCommon clinical signsMechanisms involvedSupplementationCortisol / HPA axisMorning fatigue, night waking, digestive problems, anxietyIntestinal permeability → LPS translocation → endotoxaemia → over-activation of the HPA axisGlutamine, zinc, rhodiola, ashwagandha, post-stress probioticsOestrogens / OestrobolomePMS, pelvic pain, breast tenderness, irregular periodsBacterial activity (β-glucuronidase) → reactivation of oestrogens in the gut → functional hyperoestrogenism2Soluble fibre, prebiotics, liver-support plants (black radish, rosemary)ThyroidFatigue, slow transit, hypersensitivities, HashimotoDysbiosis → impaired T4→T3 conversion + reduced absorption of cofactors (zinc, selenium) + intestinal permeability³ → immune dysregulationSelenium, iodine, temporary exclusion (gluten, lactose), immune-regulating probioticsTestosteroneFatigue, reduced libido, diffuse pain, irritabilityChronic dysbiosis → low-grade inflammation via the gut-liver axis⁴Digestive anti-inflammatories, mucosal support, suitable physical activity
The mechanism: some bacteria produce β-glucuronidase, an enzyme that blocks the elimination of oestrogens by promoting their reabsorption in the gut, which raises their circulating concentration and may contribute to functional hyperoestrogenism2.
Conclusion: thinking about the endocrine system differently to sharpen your care
When tests are “normal” but symptoms persist, revisiting the endocrine system as a whole often opens up new avenues.
That is exactly the value of an integrative approach: cross-referencing the hormonal axes, the digestive terrain, the inflammatory load and the quality of elimination.
The links between the microbiota and hormonal regulation now offer concrete markers to understand functional imbalances better and respond to them precisely.
To find out more about how we can help you support your patients even better, do get in touch!
