Johannes D. Veldhuis, MD


March 15, 2000

In This Article

Ensemble View of Neuroendocrine Axis in Aging

The central nervous system (CNS) regulates the pituitary gland, which secretes hormones to target tissues that, in turn, produce substances that feed back on the hypothalamic-pituitary axis. This feedback-control network can be assessed via novel entropy statistics, which assess the ensemble synchrony of a feedback axis. Entropy calculations quantify the progressive age-related loss of orderliness of single-hormone secretion for GH, ACTH, LH, and insulin, as well as the erosion of coordinate 2-hormone secretion for ACTH-cortisol, LH-testosterone, LH-FSH, and LH-prolactin.[1] LH secretion, sleep-stage transitions, and nocturnal penile tumescence (NPT) oscillations also exhibit marked loss of synchrony with aging.

Unknown mechanisms link aging-related parallel declines in the GH-IGF-I axis (somatopause), gonadal axis (gonadopause), and adrenal androgen secretion (adrenopause). Epidemiologic studies reveal consistent decrements in adrenal androgen (DHEA and DHEA-S) secretion in aging men and women.[6,7,8] However, neither the basis for nor the medical implications of this attrition in the adrenal zona-fasciculata function are known.