Condition: Thyroid Health

Overt hypothyroidism means a raised TSH together with a low free T4, and it is treated by replacing the missing hormone. The ATA task force guideline sets levothyroxine as the standard of care, dosed to bring TSH into the reference range, with a full replacement dose of roughly 1.6 micrograms per kilogram per day and lower starting doses in older people or those with heart disease. Restoring normal levels reverses the fatigue, cold intolerance, weight gain and cognitive fog of the underactive state. The guideline treats T4 monotherapy as first line and finds the evidence does not support routine desiccated thyroid extract or combination T4 plus T3.

The TRUST trial randomized 737 people aged 65 and over with subclinical hypothyroidism (TSH 4.60 to 19.99 with a normal free T4) to levothyroxine or placebo for a year. Levothyroxine brought the mean TSH from 6.4 down to 3.6, but the change in the Hypothyroid Symptoms score was 0.2 in both groups (between-group difference 0.0), and the Tiredness score barely differed (difference 0.4 on a 100-point scale, well under the 9-point threshold that would matter). No benefit appeared on the secondary outcomes either. This is the trial that reframed the reflex to treat a slightly high TSH.

Feller and colleagues pooled 21 randomized trials of 2,192 non-pregnant adults with subclinical hypothyroidism. Thyroid hormone reliably lowered TSH into the reference range, but the standardized mean difference was -0.11 for quality of life (95% CI -0.25 to 0.03) and 0.01 for thyroid-related symptoms (95% CI -0.12 to 0.14), both indistinguishable from no effect. The authors, grading the evidence moderate to high, concluded the findings do not support routine thyroid hormone therapy for subclinical hypothyroidism. The trials excluded pregnancy and were light on very high TSH values, so the conclusion is about the mild, common case.

Zimmermann and Boelaert review iodine deficiency as the most common preventable cause of thyroid enlargement and hypothyroidism globally, and, when it occurs in pregnancy, of preventable impairment of the developing brain. Salt iodization has made overt deficiency uncommon in many countries, so for most readers the practical point is adequacy rather than supplementation: iodized salt, dairy and seafood usually cover it. Pregnancy and breastfeeding raise the requirement, which is why prenatal advice often includes iodine. This is a U-shaped nutrient, and the harm from taking too much is the mirror image finding covered separately.

The ATA hyperthyroidism guideline covers Graves' disease, toxic nodules and thyroiditis. For Graves', the three definitive options are antithyroid drugs (methimazole preferred outside the first trimester of pregnancy, where propylthiouracil is used), radioactive iodine ablation, and thyroidectomy, each with its own tradeoffs in remission rate, later hypothyroidism and suitability. Beta-blockers control the palpitations and tremor while a definitive treatment takes effect. The guideline is a shared decision framework rather than a single answer, which is why this belongs with an endocrinologist and not with supplements.

Grozinsky-Glasberg and colleagues pooled 11 randomized trials with 1,216 patients comparing T4 plus T3 against T4 alone for hypothyroidism. No difference emerged on bodily pain, depression, anxiety, fatigue (SMD -0.12), quality of life, body weight or lipids, and adverse events were similar, so the review concluded monotherapy should remain the treatment of choice. Some patients in individual trials reported preferring the combination, and interest continues in whether a subgroup benefits, so this is an area of live research rather than a closed door. It is a discussion to have with a prescriber, not a reason to buy T3 online.

Wichman and colleagues pooled 16 controlled trials of selenium in autoimmune thyroiditis. In patients already on levothyroxine, selenium lowered TPO antibodies by a weighted mean of 271 units at 3 months (95% CI -366 to -175), holding at 6 and 12 months; in untreated patients the antibody fall appeared at 3 months but not consistently later. The authors rated the quality of evidence low overall and noted the selenium groups had a significantly higher risk of reporting adverse effects. Their own conclusion was explicit that whether the antibody drop maps onto anything a patient would notice remains to be demonstrated. Selenium is also a narrow-window nutrient, so more is not better.

Krysiak and colleagues studied 34 drug-naive women with Hashimoto's thyroiditis who were incidentally found to have positive anti-tissue-transglutaminase antibodies, a marker associated with celiac disease. Sixteen followed a gluten-free diet for 6 months and 18 did not. The gluten-free group showed lower TPO and thyroglobulin antibody titers and a small rise in vitamin D, while thyroid function tests changed little. This is a small, non-randomized pilot in women who already carried a celiac-related antibody, with antibody levels rather than symptoms or thyroid function as the outcome, so it cannot support a blanket gluten-free recommendation for Hashimoto's. The clear indication for a gluten-free diet remains diagnosed celiac disease, which is more common in autoimmune thyroid disease and worth testing for.

The TABLET trial screened 19,585 women and randomized 952 who were euthyroid but thyroid-peroxidase-antibody positive with a history of miscarriage or infertility to levothyroxine 50 micrograms daily or placebo, from before conception through pregnancy. Live birth after 34 weeks was 37.4% on levothyroxine and 37.9% on placebo (relative risk 0.97, 95% CI 0.83 to 1.14), with no difference in miscarriage or preterm birth. Overt thyroid disease in pregnancy is a different matter and is treated, but this trial closed the case on giving levothyroxine to antibody-positive women whose thyroid function is normal.

The ATA guideline for thyroid nodules and differentiated thyroid cancer notes that nodules are very common, especially with age and on imaging done for other reasons, and that about 7 to 15 percent turn out to be malignant. Evaluation rests on a TSH check and neck ultrasound, with the ultrasound pattern guiding whether and when a fine-needle aspiration biopsy is needed; many small, low-risk nodules are simply watched. The features that raise concern, and belong in the hands of a doctor promptly, are a nodule that is enlarging quickly, is hard or fixed, or comes with a hoarse voice or trouble swallowing.

Singh and colleagues gave 20 patients on stable levothyroxine 1,200 mg of elemental calcium as calcium carbonate with their tablet for three months: free and total T4 fell and mean TSH rose from 1.6 to 2.7 mIU/L, with one in five patients pushed above the reference range, all reversing when the calcium was stopped. Benvenga and colleagues showed espresso coffee lowered the rise in serum T4 after a dose by about a third compared with water, and dietary fiber interfered more strongly. The practical rule that follows is to take levothyroxine on an empty stomach with water, ideally 30 to 60 minutes before food and coffee, and to separate calcium and iron supplements by about four hours.