Table 3.
Population parameters for the final model.
| Models and parameters | Estimate | Relative SE | Brief definition of symbols |
|---|---|---|---|
| System model for ACTH | |||
| Amplitude AM surge (pmol h−1) | 87 | 33% | Maximum production rate l−1 of ACTH distribution volume |
| Width AM/PM surge (h) | 1.32 | 13% | Surge width (same for AM and PM) |
| Time AM surge (h:min) | 07:18 | 00:06* | Clock time for morning surge |
| kout ACTH (h−1) | 4.68 | 24% | First order elimination rate constant for ACTH |
| BaselineACTH (pmol l−1) | 2.58 | 7% | Baseline concentration of ACTH in the absence of surges and without drug |
| Amplitude PM surge (pmol l−1) | 10 | 20% | Maximum production rate l−1 of ACTH distribution volume |
| Time PM surge (h:min) | 16:18 | 00:20* | Clock time for afternoon surge |
| ω Baseline | 27% | 24% | Interindividual variability for baseline (%CV) |
| ωkout | 38% | 19% | Interindividual variability for kout (%CV) |
| σ | 32% | 11% | Proportional error (%CV) |
| Drug model | |||
| Imax1 (−) | 0.277 | 21% | Maximum fractional inhibition of ACTH baseline production |
| Imax2 (−) | 1 | fixed | Maximum fractional inhibition of ACTH surge production |
| IC50, 1 and 2 (µg l−1) | 0.325 | 87% | Concentration of drug causing 50% of the maximum suppression |
| ωIC50, 1 and 2 | 170% | 36% | Interindividual variability for IC50,1 and 2 (%CV) |
| System model for cortisol | |||
| Amax (nmol h−1) | 298 | 7.8% | Maximum production rate l−1 of cortisol distribution volume |
| A50 (pmol l−1) | 4.96 | 14% | ACTH concentration where cortisol production is half-maximal |
| γ | 4.10 | 19% | Sigmoidicity factor for ACTH-cortisol production relationship |
| kout,cortisol (h−1) | 0.366 | 24% | First order elimination rate constant for cortisol |
| ωkout,cortisol | 49% | 30% | Interindividual variability for kout,cortisol (%CV) |
| ω A50 | 38% | 19% | Interindividual variability A50 (%CV) |
| σ | 33% | 16% | Proportional error (%CV) |
*
SE, not relative SE.