Table 1.
Estradiol levels in women were obtained in the (early) follicular phase of the menstrual cycle.
Figure 1.
An example of measured 24-hr 10-minute interval serum hormone profiles.
The dark line in the upper figure represents ACTH; the estimated secretion is shown by the dark bars in the lower panel. In this system, ACTH pulses drive or elicit pulses of cortisol pulses with a delay of approximately one time unit. Cortisol (light line, scaled by factor 0.1) also receives some pulse stimuli from auxiliary inputs as not all cortisol pulses are preceded by an ACTH pulse (see the lower figure).
Figure 2.
Schematic depiction of the simulated regulatory mechanisms in episodic secreting hormones.
(1) Shows a mechanism in which a pulse in triggers a pulse in
. (2) Shows a mechanism that triggers a pulse to be released in
when
falls below a (preset) threshold. (3) Shows a mechanism that inhibits the pulse amplitude in
when the concentration in
is above a (preset) threshold. (4) Shows that combining mechanisms (1) and (2) appear as mechanism (1).(5) Depicts a diurnal pattern that is maintained by another (shared) variable.
Figure 3.
Pulses in induce pulses in
after 1 lag, without auxiliary (noise) pulses in
.
The solid black lines represent the cross correlation profiles after conditioning on , the dashed lines after conditioning on pulses in
.
Figure 4.
Pulses in induce pulses in
after lags of 1 or 2 (randomly drawn with an equal probability).
In AM3 and AM4 the solid line is related to conditioning on pulses of and the dashed line on the pulses of
.
Figure 5.
Overview of the metrics on the HPA axis hormones ACTH and cortisol.
The shaded area around the white lines marks the 95% confidence interval of the mean, the thin lines show the individual results. The four metrics unanimously point to lag 1, but the different metrics center on different aspects of the relation between ACTH and cortisol.
Figure 6.
A concentration drop of below a certain threshold induces a pulse in
.
In AM3 and AM4 the solid line marks the conditioning on pulses of and the dashed line the pulses of
.
Figure 7.
The association metrics for a two hormone system in which increased concentrations of diminish the pulse amplitudes of
by 90%.
Figure 8.
The association metrics in a system in which drives
with a time lag of one and
acts as an inhibitor when the concentration of
exceeds a certain threshold such that the new pulses in
are reduced by 90%.
Figure 9.
The association metrics of simulated concentration profiles from a simple system of two hormones exhibiting diurnal patterns, but without direct activation or inhibition.
Figure 10.
Overview of association metrics of ACTH and TSH.
The shaded area around the white lines marks the 95% confidence interval of the mean, the thin lines show the individual results. The metrics point at a relation at two optima at lags −42 and 22.