Your TSH is "normal." You still feel awful. You are not crazy. The test was incomplete.

TSH measures the brain's signal to the thyroid, not what the thyroid is actually producing or what your tissues are receiving. In healthy thyroid function, TSH correlates well with thyroid hormone levels — but in autoimmune thyroid disease, especially during the variable early stages and in patients on replacement, TSH can normalise even when free T4 or free T3 is suboptimal. A complete picture requires free T4, free T3, and antibodies (TPO and thyroglobulin). Evidence level: Strong, though clinical practice in the US still lags.

Additionally, conversion from T4 (the storage hormone, what levothyroxine provides) to T3 (the active hormone) is variable between patients — affected by genetics (DIO2 polymorphisms), nutrient status (selenium, zinc, iron, ferritin), inflammation, and other medications. Some patients on levothyroxine have a normal TSH and free T4 but a low free T3 and persistent symptoms. Without measuring free T3, that's invisible. The American Thyroid Association doesn't routinely recommend free T3 in monitoring, which is part of why endocrinologists often resist it. That said, you're allowed to ask for it, and many integrative endocrinologists order the full panel as standard.

Honest answer: it's controversial. Reverse T3 (rT3) is an inactive form of T3 that competes with active T3 at the receptor. The functional medicine framing is that high rT3 indicates poor T4-to-T3 conversion, often in the setting of stress, illness, or low ferritin, and that the free T3 to reverse T3 ratio matters more than free T3 alone. The conventional endocrinology view is that rT3 isn't clinically actionable — it's elevated in a wide range of non-thyroid illnesses (called non-thyroidal illness syndrome) and treating it with T3 medication has minimal trial evidence. Evidence level: Weak, with reasonable disagreement between camps.

My honest take: rT3 in isolation is rarely diagnostic, but in a complete panel — alongside symptoms, free T4, free T3, antibodies, and ferritin/iron status — it can add context. If your free T4 is mid-range, your free T3 is low-normal, your rT3 is high, and your ferritin is 30, that pattern tells a different story than free T3 alone. It just shouldn't be the test you hang your treatment on. If a clinician is making big medication changes based on rT3 numbers without the rest of the picture, be a little skeptical.

Levothyroxine (T4 monotherapy) is the standard, and for the majority of patients it normalises labs and resolves symptoms. For a meaningful subset — estimated 10–20% — symptoms persist despite normal labs on T4 alone. Multiple trials have looked at adding T3 (liothyronine), and the results have been mixed. A 2022 meta-analysis suggested no clear average benefit but acknowledged a subgroup of patients does meaningfully better on combination therapy, possibly those with DIO2 polymorphisms or specific symptom profiles. Evidence level: Mixed; subgroup evidence is real.

Natural desiccated thyroid (NDT — Armour, NP Thyroid, Nature-Throid) provides T4, T3, and other thyroid components from porcine glands. It's not standardised the way synthetic medications are, but it's not unsafe — it's been used for over a century. The largest trial comparing NDT to levothyroxine (Hoang et al, 2013) found no average difference in cognition or mood, but nearly half the patients preferred NDT. Evidence level: Weak-to-Moderate, with strong patient preference signal. Reasonable approach: try optimised levothyroxine first, including dose timing (away from food, calcium, iron, coffee). If symptoms persist with truly optimised T4 monotherapy, T3 addition or a trial of NDT is reasonable to discuss — and you may need to find a different doctor to do it.

Selenium has the most evidence of any supplement in Hashimoto's. Multiple trials show that 200 mcg/day of selenium (selenomethionine form) reduces TPO antibody levels over 3–6 months, with possible symptom benefit. It does not cure Hashimoto's, and the antibody reduction doesn't always translate to clinical improvement, but the safety profile is excellent at this dose. Evidence level: Moderate. Important: selenium toxicity is real above 400 mcg/day chronically — if you eat a lot of Brazil nuts, factor that in.

Gluten is more nuanced. Patients with Hashimoto's have a higher rate of celiac disease (3–5x baseline), so screening with tTG-IgA plus total IgA is reasonable. For non-celiac gluten removal, the evidence is weaker — a few small studies suggest antibody reduction in some patients, but trials are inconsistent. The honest framing: if you've ruled out celiac and want to trial 3 months gluten-free, that's reasonable. It's not necessary for everyone with Hashimoto's, despite what social media suggests. The same is true of other elimination diets (AIP, dairy-free) — they help some patients meaningfully and don't help others, and they aren't required treatment.

There's a real biological story and a wellness-marketing story, and they're not the same. The biological story: a substantial portion of T4-to-T3 conversion happens in the gut, mediated by gut bacteria. Intestinal inflammation, dysbiosis, and increased intestinal permeability ("leaky gut" — a real but often misused term) affect thyroid hormone metabolism. SIBO is more prevalent in hypothyroid patients — both because hypothyroidism slows motility, and because the autoimmune environment makes gut dysfunction more likely. Evidence level: Moderate for the connection; weaker for any specific protocol.

What's reasonable: address gut symptoms if you have them (test for SIBO if symptoms suggest it, screen for celiac, consider stool testing if you have persistent GI issues). Standard reasonable steps include adequate fiber, fermented foods if tolerated, addressing constipation (which slows medication absorption), and treating any diagnosed gut issues. What's overhyped: "gut-thyroid protocols" with $400 supplement stacks, expensive stool tests with proprietary algorithms, and the claim that healing your gut will eliminate the autoimmune disease. Hashimoto's, once present, generally doesn't go away — but residual symptoms can absolutely improve when associated gut issues are addressed.

Rising TPO and thyroglobulin antibodies in a patient with normal TSH usually indicates active autoimmune attack on the thyroid that hasn't yet resulted in significant hormone disruption. Over time, this often progresses — but not always, and not predictably. Patients can spend years or decades with elevated antibodies and stable thyroid function. Evidence level: Strong on the pathology, weaker on what to do about it preemptively.

What to do depends on context. If you're asymptomatic, monitoring (TSH, free T4, sometimes free T3 every 6–12 months) is standard. If you're symptomatic with normal labs — fatigue, weight change, hair loss, brain fog — the question becomes whether you have subclinical hypothyroidism that hasn't shown on TSH yet, or whether other causes are driving symptoms. Some endocrinologists will trial low-dose levothyroxine in this scenario; others won't until TSH is clearly elevated. Selenium is reasonable to discuss for antibody reduction. So is addressing modifiable factors: stress, sleep, ferritin/iron, vitamin D, gluten if celiac is positive. "Antibodies don't matter" is an outdated take — they matter for prognosis and risk monitoring, even if they don't dictate treatment today.