Hypothyroidism is one of the most commonly over-diagnosed and simultaneously most commonly under-treated conditions I encounter. The over-diagnosis comes from interpreting borderline TSH values without clinical context. The under-treatment comes from checking only TSH and missing the complete picture — and from assuming that a normal TSH means someone with all the symptoms is imagining them.
This article is for the patient who has been told their thyroid is “fine” but who is exhausted, gaining weight without explanation, losing hair, feeling cold, and constipated. And for the patient who is on levothyroxine but still feels the same. Both groups deserve a more complete answer.
The problem with testing only TSH
TSH (thyroid-stimulating hormone) is secreted by the pituitary gland to tell the thyroid how much thyroid hormone to make. It is an indirect measure — it reflects the pituitary’s reading of thyroid hormone levels, not the actual thyroid hormone activity in the tissues.
The thyroid produces mainly T4 (thyroxine), which is a storage form. T4 must be converted to T3 (triiodothyronine) in the liver, kidneys, and gut before it becomes metabolically active. Some people have normal TSH and normal T4 but impaired T4-to-T3 conversion — their cells are genuinely low in active thyroid hormone, but this shows up nowhere in a TSH-only test.
Conditions that impair T4-to-T3 conversion: chronic stress and high cortisol, selenium deficiency (very common in India), iron deficiency, zinc deficiency, gut dysbiosis, and chronic inflammation. All of these are common in the patients I see with persistent hypothyroid symptoms despite a normal TSH.
Hashimoto’s thyroiditis — the cause most people are never told about
The most common cause of hypothyroidism in India (as everywhere) is Hashimoto’s thyroiditis — an autoimmune condition where the immune system attacks the thyroid gland. The diagnosis requires testing for TPO antibodies and thyroglobulin antibodies, which are not on a standard thyroid panel.
This distinction matters because Hashimoto’s is not just a thyroid problem — it is an immune dysregulation problem. Many Hashimoto’s patients have other autoimmune conditions or gut permeability issues. The approach needs to address the immune component, not just the hormone level. Treating only the TSH in someone with Hashimoto’s is like changing the oil warning light without addressing why the oil pressure is low.
I check TPO antibodies in every patient with hypothyroid symptoms, a family history of thyroid disease, or any other autoimmune condition. Finding Hashimoto’s changes the conversation from “take levothyroxine and recheck in six months” to a broader discussion about diet, gut health, selenium, stress, and immune modulation.
Selenium — the most important nutrient for thyroid function that most people have never heard of
Selenium is required for both thyroid hormone synthesis and for T4-to-T3 conversion. The thyroid gland has the highest selenium concentration of any organ in the body. India’s soils are selenium-depleted in most regions, and the Indian vegetarian diet has very limited selenium sources (Brazil nuts, the best source, are not part of Indian cuisine; meat and seafood, which are good sources, are avoided by many).
Selenium deficiency is common in India and directly impairs thyroid function. In some studies, supplementation at 200 mcg daily reduced TPO antibody levels by up to 40% over six months in Hashimoto’s patients, though the evidence is not consistent and supplements should only be taken on your doctor’s advice. I check selenium levels before supplementing, but I have a low threshold for supplementation in Indian vegetarians with thyroid issues.
Why some people feel no better on levothyroxine
Levothyroxine (T4) is the standard treatment for hypothyroidism. For most people, it works well. For some, it does not — their TSH normalises, but symptoms persist. The most common reason: impaired T4-to-T3 conversion means the T4 they’re taking is not being adequately converted to active T3.
Options in this situation: address the conversion barriers (stress, selenium, iron, gut health), consider combination T4/T3 therapy (desiccated thyroid extract or a separate T3 medication), and ensure the levothyroxine is being taken correctly — always on an empty stomach, 30–60 minutes before food, and not within four hours of calcium, iron, or antacids, all of which impair absorption significantly.
Diet and thyroid — what the evidence actually says
Gluten: There is a well-documented association between Hashimoto’s and coeliac disease (they share an immune mechanism). For patients with both conditions, a strict gluten-free diet reduces antibody levels. For Hashimoto’s patients without coeliac disease, the evidence is weaker — but I see a meaningful subset of patients who report significant symptom improvement on a gluten-reduced diet even without diagnosed coeliac disease.
Raw cruciferous vegetables: Large amounts of raw cruciferous vegetables (broccoli, cabbage, radish, mustard leaves) can impair thyroid hormone synthesis in people with iodine deficiency by competing with iodine uptake. At typical dietary amounts and when cooked, this is not a concern for most people. The risk is primarily from large quantities of raw cruciferous (juicing cabbage or radish daily), not from eating sabzi.
Soy: Soy isoflavones can interfere with thyroid hormone absorption if taken close to levothyroxine. Keeping a gap of four hours between soy-containing food and the medication resolves this.
Iodine: India fortifies salt with iodine and outright iodine deficiency is uncommon in urban areas. Excess iodine from supplements can worsen Hashimoto’s. Do not supplement iodine without a tested deficiency.
When to get checked and what to ask for
If you have unexplained fatigue, weight gain, hair loss, cold intolerance, constipation, dry skin, brain fog, or low mood — ask for TSH, Free T3, Free T4, and TPO antibodies. Not just TSH. If a doctor tells you your “thyroid is fine” based only on TSH, ask for the full panel. This is not an unusual request — it is standard of care for anyone with thyroid symptoms.
