Thyroid

Score the degree of systemic decompensation in suspected thyroid storm — a clinical diagnosis that biochemistry alone cannot make.

Convert free T4 between ng/dL, pmol/L and ng/L, and see why the interval belongs to the assay rather than to the patient.

Correct total T4 for binding-protein changes using T3 uptake — the historical workaround for a direct free T4 assay.

Convert free T3 between pg/mL, pmol/L and ng/L, and see why the commonest low FT3 is non-thyroidal illness rather than hypothyroidism.

Estimate peripheral T4-to-T3 conversion from free T3 and free T4 — a marker with no validated reference interval.

Estimate a starting levothyroxine dose from body weight and clinical situation, from cautious elderly starts to TSH suppression.

Interpret an existing levothyroxine dose in liothyronine-equivalent terms, using the published but contested potency ratios.

Calculate nodule or lobe volume from three ultrasound measurements using the ellipsoid formula, since growth is defined by volume, not diameter.

mIU/L, µIU/mL and mU/L are the same number for TSH. That is the answer; the rest of this page is the interpretation, which is where TSH is actually difficult.