Table 1 Equations of the estimated and measured 24-h urinary iodine excretion

Iodine: creatinine ratio (μg/g)

I/Cr

UIC (μg/L) / UCr (g/L)

Measured 24-h urine iodine excretion (μg/d)

Measured 24hUIE

24hUIC (μg/L) × 24 h urine (L)

Estimated 24-h urine iodine excretion¹ (μg/d)

Estimated 24 h UIE¹

I/Cr (μg/g) × Pr24hCr (g/d)

Pr24hCr (g/d) = 24hUCr (g/L) × 24 h urine (L)

Estimated 24-h urine iodine excretion² (μg/d) (Tanaka T, et al.[31])

Estimated 24 h UIE²

I/Cr (μg/g) × Pr24hCr (g/d)

Pr24hCr (mg/d) = [(− 2.04 × age (year)] + [(14.89 × weight

(kg)] + [16.14 × height (cm)]—2244.45

Estimated 24-h urine iodine excretion³ (μg/d) (Kawasaki T, et al.[32])

Estimated 24 h UIE³

I/Cr (μg/g) × Pr24hCr (g/d)

Males:

Pr24hCr (mg/d) = [− 12.63 × age (year)] + [15.12 × weight

(kg)] + [7.39 × height (cm)]—79.9

Females:

Pr24hCr (mg/d) = [− 4.72 × age (year)] + [8.58 × weight (kg)]

+ [5.09 × height (cm)]—74.5

Estimated 24-h urine iodine excretion⁴ (μg/d) (Mage, et al.[33])

Estimated 24 h UIE⁴

I/Cr (μg/g) × Pr24hCr (g/d)

Males:

Pr24hCr (mg/d) = 0.00179 × [140—age (year)] × [weight

(kg)^1.5 × height (cm)^0.5] × [1 + 0.18 × A × [1.366–0.0159 ×

BMI (kg/m²)].

Females:

Pr24hCr (mg/d) = 0.00163 × [140—age (year)] × [weight

(kg)^1.5 × height (cm)^0.5] × [1 + 0.18 × A × [1.429–0.0198 ×

BMI (kg/m²)]; where A is African American or black race = 1,

other race = 0

Estimated 24-h urine iodine excretion⁵ (μg/d) (Knudsen N, et al.[27])

Estimated 24 h UIE⁵

I/Cr (μg/g) × Pr24hCr (g/d)

Males:

pr24hCr (g/d) = 1.74 g (25–49 years), 1.63 g (50–59 years)

Females:

pr24hCr (g/d) = 1.23 g (25–49 years), 1.15 g (50–59 years)

Estimated 24-h urine iodine excretion⁶ (µg/d) (IOM[34])

Estimated 24 h UIE⁶

iodine excretion (µg/d) = 0.9 × iodine intake (µg/d)

iodine intake (µg/d) = spot UIC (µg/L)/ 0.92 × (0.0009 L · h⁻¹

· kg⁻¹ · 24 h · d⁻¹) × weight (kg)