Altered pulsatile and coordinate secretion of pituitary hormones in aging: Evidence of feedback disruption

A novel thesis is that healthy aging of neuroendocrine axes is marked by disruption of orderly patterns of hormone release (1). This can be quantified by a recently validated approximate entropy statistic applied to 24-hour hormone profiles, e.g., luteinizing hormone (LH), and growth hormone (GH). Moreover, more subtle disturbances of feedback control are indicated by decreased conditional regularity or synchrony (higher cross-approximate entropy) within coupled axes, such as ACTH-cortisol, LH-testosterone, etc. Such alterations can precede any changes in mean serum hormone concentrations, thus highlighting an impact of age on the feedback control mechanisms that coordinate the flow of signaling information within a neuroendocrine axis or network.