This shows how all hormonal systems are coordinating together in perfect synchronization like a symphony orchestra. The hypothalamic  pituitary axis is just one of the systems in this category. Neurohormonal regulation is reflected in VLF or very low frequency.  LF and HF are like fast speed internet and can make adjustments very fast.  As we age VLF increases.   VLF also increases with prolonged mental/emotional stress and metabolic imbalances like glycemic dysregulation, lipid problems and other metabolic issues. The VLF will be elevated when the autonomic nervous system is maxed out.