The Hypothalamic-Pituitary-Thyroid Axis in Infants and Children: Protection from Radioiodines

Table 1

Selected physiology values in infants, children, and young adults.

	Age (days)	Value	Age (months)	Value	Age (years)	Value	Age (years)	Value	References
Blood flows (L/hr/kg bw)^a
Cardiac output	6	11.1^b	10.6	8.6^c	6	11.1	18	8	[1, 2]
Alveolar ventilation	1	13.4	3	8.7	6	6.9	18	6.7^d	[3]
Glomerular filtration	2	0.09^b	12	0.18	3	0.17	12	0.13	[4]
Blood flow to brain	1	3.2	12	4.3	5	2.9	15	0.83	[5]
Blood flow to kidney	1	1.9	12	1.4	5	1.8	15	1.1	[5]
Blood flow to thyroid	—	—	—	—	—	—	18	0.13^e	[6]
Organ volumes (L/kg bw)^a
Body weight (Kg)	1	3.4	12	9.8	6	21.1	18	54.4	[7]
Blood	1	0.088	24	0.046	6	0.081	18	0.077	[7]
Brain	1	0.10	12	0.091	6	0.057	18	0.024	[7]
Kidney	1	0.007	12	0.0066	6	0.0052	18	0.0044	[7]
Thyroid	1–30	0.3–0.4𝐸−3	12–24	0.2–0.3𝐸−3	5–9	0.2–0.3𝐸−3	15–19	0.3𝐸−3	[8]

aBody weight for females at specified ages calculated using equation from [7].
^bCalculated using body weight at birth.
^cCalculated using body weight of 1 year old.
^dDerived values using respiratory frequency, tidal volume, and physiological dead space [3].
^eCalculated based on reported percentage of blood flow to thyroid in adult humans (1.6% of cardiac output) [6] and cardiac output (8 L/hr/kg bw) in females of 18 years old.