What GAPS Means by Calling Gut Flora an Endocrine Organ

Calling gut flora an “endocrine organ” is a way of describing its effects on hormonal signaling. In Gut and Physiology Syndrome, Dr. Natasha Campbell-McBride develops that idea through three routes: nourishment, protection and substances produced or modified by microbes. It brings the digestive system into the hormone discussion instead of looking at each gland in isolation.^[1]

The Gut and Its Microbes Are Related, but Different

The gut contains human cells that produce hormones, as well as a community of microbes. When the book discusses hormones made in the gut and hormonal substances produced by microbes, those are related observations, not a claim that bacteria make every human hormone.^[1]

That distinction helps with the language. “The gut” can mean an organ and its tissues. “Gut flora” means the microbial community. A study about one does not automatically measure the other.

Route One: Digestion and Absorption

Endocrine tissues need usable nutrients. The book connects the gut community with food processing, the intestinal lining and nutrient availability, then follows that connection to glands making their own hormones. The route is indirect as well as direct: a microbe does not have to manufacture a finished hormone to affect the conditions in which a gland works.^[1]

This is why the GAPS discussion returns to both food quality and digestion. The digestion and absorption guide explains the journey from a meal to usable nutrients; the vitamin-production guide covers the separate question of what microbes make.

Route Two: Protection From Unwanted Substances

Campbell-McBride describes gut flora helping protect the body from incoming substances and influencing the products generated within the bowel. She connects an altered microbial environment with a changed burden on endocrine tissues.^[1]

In that framework, the household environment and the digestive system belong in the same discussion. They are still different questions: which substance is present, what exposure occurred and how the person’s body responds. The endocrine-disruptor guide keeps those questions specific.

Route Three: Microbial Signaling

The book discusses microbes producing or modifying active substances that interact with the endocrine system. It also describes hormonal feedback affecting the microbial environment. This is a two-way relationship, rather than a one-way command from the gut to every gland.^[1]

A 2014 review listed in the book’s hormone references explores the microbiota as an endocrine organ, including hormone-like substances and interactions with the host’s hormonal output. It is a review of mechanisms and research, not a clinical test for identifying a person’s hormone problem.^[2]

What the Organ Comparison Helps Explain

The comparison is useful because it connects several processes that are easy to separate on paper: food, microbial activity, hormone signaling and distant organs. The book’s strong emphasis on gut flora expresses its GAPS framework; it does not provide a measured ranking in which the gut is always “more powerful” than the thyroid or pancreas.^[1]

For a specific question, continue with thyroid function or sex hormones. Those guides keep the actual hormone and clinical situation in view.

Using the Idea in Everyday GAPS

Start with the food phase you are following and the change you are actually observing. A useful note records what changed and when. It does not need to assign a microbial species to a tired day or interpret a bowel movement as a hormone measurement.

For meals, use the Full GAPS meal guide or the appropriate Intro stage guide. The food sequence remains the guide to the plate, even when you are reading about a broader mechanism.

If you would like one place to keep food and symptom observations, a simple diary can help you compare days without relying on memory. The 90-Day Family Food Diary is listed in my printable catalog.

For the wider picture, return to the GAPS hormones and endocrine-health guide.

References

1. Campbell-McBride, N. Gut and Physiology Syndrome (2020), “Hormones,” the three gut/endocrine routes; “Production of vitamins and hormones”.
2. Clarke G, Stilling RM, Kennedy PJ, Stanton C, Cryan JF, Dinan TG. Minireview: Gut Microbiota: The Neglected Endocrine Organ. Molecular Endocrinology. 2014;28:1221–1238. Listed as reference 25 in the book’s “Hormones” bibliography.