What Functional Testing Actually Finds

Sarah had Hashimoto’s thyroiditis with impaired T4→T3 conversion, driven by autoimmune inflammation and multiple nutrient deficiencies. Her TSH sat within the standard reference range — which extends to 4.5 mIU/L — but was almost three times the functional optimal. The GP had no visibility of the antibodies, the conversion problem, or the nutrient deficiencies because none of them were on the standard panel.

James’s glucose appeared normal because his pancreas was producing four times the optimal amount of insulin to maintain it. That compensatory hyperinsulinaemia is invisible on a fasting glucose test. He was 3–5 years from a type 2 diabetes diagnosis, had established fatty liver, and the atherogenic lipid pattern that doesn’t show on a total cholesterol number. The standard panel had looked at the consequence of insulin (glucose) rather than the insulin itself.

The integration insight: H. pylori was the root driver. It was suppressing stomach acid (explaining the low ferritin and bloating), contributing to gut permeability, and allowing yeast to establish. The elevated beta-glucuronidase explained why oestrogen was accumulating despite age-related decline — gut bacteria were deconjugating it and returning it to circulation. The chronic HPA dysregulation was blocking thyroid conversion, explaining why her TSH looked “normal” while her cells were starved of active T3. No single test showed this. All five together made it legible.

Catherine’s anxiety and sleep disruption were directly attributable to progesterone deficiency — progesterone is the brain’s primary calming neurosteroid. Her oestrogen metabolite pattern, invisible on a standard oestrogen blood test, pointed toward a specific methylation and detoxification support need rather than just HRT. Two women with identical blood oestrogen levels can have completely different risk profiles depending on how that oestrogen is metabolised. This is why the DUTCH Plus exists.

Twenty years in printing (solvent exposure). Amalgam fillings placed in his twenties. Victorian house with original pipework. Regular consumption of his own angling catch (potential mercury accumulation from large freshwater fish). None of this was asked about in any specialist consultation.

The OAT revealed that David’s cells were under severe oxidative assault with depleted antioxidant defences — a picture consistent with sustained toxic exposure. Provoked urine metal testing (DMSA challenge) subsequently confirmed significant retention of metals consistent with his occupational and dietary history. Standard blood metal testing had been negative precisely because metals are stored in tissue, not serum.

Mark had treated the overgrowth twice without addressing why it kept re-establishing. The impaired migrating motor complex — the interdigestive “housekeeping wave” that clears the small intestine between meals — was allowing bacteria to accumulate faster than antimicrobials could clear them. Low stomach acid was failing to sterilise incoming food adequately. And starting probiotics immediately post-antimicrobials had fed the residual overgrowth rather than restoring the commensal ecology.