Thyroid's secretory capacity

The secretion of thyroid (GT, as Inkretionsleistung or, if calculated from hormone levels as Spina GT hereinafter) defines the maximum amount of stimulated thyroxine, which may distribute the thyroid gland in a second.

Determination

Experimentally, the secretion can be determined by the T4 output of the thyroid gland is measured after stimulation with a high concentration of TSH.

In vivo can SPINA - GT with

Or

Be calculated from serum levels of TSH and free or total thyroxine.

Constant parameters of the equations are:

Dilution factor for T4 ( reciprocal of the apparent volume of distribution, 0.1 l -1): Clearance exponent for T4 ( 1.1e -6 sec -1) K41 Dissociation constant T4 - TBG ( 2E10 l / mol) K42 Dissociation constant T4 - TBPA ( 2e8 l / mol) DT: EC50 for TSH (2.75 mU / l)

Reference ranges

The equations and their parameters are calibrated for adults with a body mass of 70 kg and a plasma volume of approximately 2.5 l

Clinical Significance

GT is increased in the case of hyperthyroidism and reduced in hypothyroidism. The secretion correlates with the specific sonographic thyroid volume and showed in a longitudinal study of a higher reliability than TSH, FT4, FT3 or. In one study, a negative correlation between GT and creatinine clearance was observed. In the initial phase of a Non- thyroidal illness syndrome may SPINA -GT passager be slightly increased.