HPA Axis Activity

Anxiety

Restlessness, racing thoughts, a wired feeling. Multiple routes reach it: neurosteroid changes at GABA-A, glucocorticoid signalling, sleep loss and thicker blood.

Fat Mass

Total body fat. It is the endpoint the whole fat-loss class is measured on, and the one place where the incretin drugs have hard trial data rather than mechanism.

Hypothalamus

The control room above the pituitary. Appetite, body temperature, the reproductive axis and the GH rhythm are all set here, which is why so many peptides that produce whole-body effects act on one small area.

Protein Breakdown

Muscle being taken apart, driven largely by cortisol at the glucocorticoid receptor. Blocking it is the anti-catabolic half of how steroids work.

Sleep Quality

How restorative sleep is, as opposed to how much of it there is. Deep and REM sleep are where growth hormone is released and where memory is consolidated, so this is the measure that connects a sleep effect to a memory effect. A person can sleep eight hours and get almost none of this.