Thyroids secretory capacity (G, also referred to as SPINA-GT) is the maximum stimulated amount of thyroxine the thyroid can produce in one second. G' is elevated in hyperthyroidism and reduced in hypothyroidism.
G is calculated with
or
: Dilution factor for T4 (reciprocal of apparent volume of distribution, 0.1 l)<br />
: Clearance exponent for T4 (1.1e-6 sec)<br />
K: Dissociation constant T4-TBG (2e10 L/mol)<br />
K: Dissociation constant T4-TBPA (2e8 L/mol)<br />
D: EC for TSH (2.75 mU/L)