Thyroid Profile (T3, T4 & TSH)

T3 (triiodothyronine) and T4 (thyroxine) are thyroid hormones that regulate metabolism; T4 is produced mostly by the thyroid and is converted into the more active T3 in tissues. TSH (thyroid‑stimulating hormone) is released by the pituitary to control thyroid hormone production. High TSH usually indicates an underactive thyroid (low T3/T4); low TSH suggests an overactive thyroid (high T3/T4).

Costs vary by country, lab and insurance. In the UK tests are typically free when done through public healthcare; privately a single TSH or a free T4/free T3 test often costs about £15–£50. In India a complete T3/T4/TSH panel commonly runs ~₹200–₹800. In the US out‑of‑pocket prices range roughly $40–$250 per test or $100–$300 for a thyroid panel. Check local labs.

If TSH, T3 and T4 are all low, this suggests central (secondary or tertiary) hypothyroidism — the pituitary or hypothalamus isn’t stimulating the thyroid — or severe non-thyroidal illness or medication effects. This requires prompt evaluation for pituitary disease and other pituitary hormones (especially cortisol) before starting therapy; pituitary imaging and endocrine referral are usually indicated.

When T3, T4, and TSH are all high — a rare pattern — it usually indicates a TSH-secreting pituitary adenoma or thyroid hormone resistance. Patients show hyperthyroid symptoms (weight loss, palpitations, heat intolerance, tremor, anxiety, increased appetite) and face complications such as arrhythmias, osteoporosis, muscle weakness and menstrual changes. Prompt endocrine evaluation and imaging are needed for diagnosis and treatment.

Yes. Significant physical or psychological stress can alter thyroid blood tests: acute stress and illness often lower TSH and reduce peripheral conversion of T4 to T3, producing a low‑T3 pattern while T4 may remain normal. These changes are usually transient (non‑thyroidal illness). Repeat testing after recovery and discuss persistent abnormalities with your clinician.

If T3 (triiodothyronine) is too low, metabolism slows, causing fatigue, weight gain, cold intolerance, constipation, dry skin, hair loss, slowed heart rate, and mental sluggishness or depression. Low T3 can raise cholesterol and increase cardiovascular risk; severe untreated deficiency may progress to myxedema and life‑threatening complications. Treating the underlying thyroid disorder usually reverses symptoms.