Table 1.

Bivariate cross-ApEn of physiologically paired LH, PRL, FSH, and T concentrations measured 576 times over 4 days

Cross-ApEn	Means ± SE	Median
Feedforward
LH-T	1.8298 ± 0.0366	1.8145
LH-prolactin	1.6262 ± 0.0615	1.6460
LH-FSH*	1.8469 ± 0.0354	1.7984
Feedback
T-LH	2.1700 ± 0.0331	2.1573
T-PRL	2.1957 ± 0.0332	2.2114
T-FSH*	2.0551 ± 0.0306	2.0916

Data are means ± SE and median (n = 12 except for FSH, where n = 11). ApEn, approximate entropy; T, testosterone; PRL, prolactin. Feedforward denotes pituitary-gonadal or pituitary-pituitary coupling, whereas feedback denotes gonadal-pituitary coupling (methods).

^*One FSH series was incomplete.