Adrenaline rushes = low adrenals. When your adrenals don't produce enough cortisol, for example to maintain blood sugar, they produce adrenaline. This brings up blood sugar, just like cortisol, but it is a last-ditch, crisis move by the adrenals / liver, and very stressful to the whole body. It is also deeply unpleasant - that sudden rush of fear / fright.

Look carefully at your diet to avoid sugar highs and lows, which stress the adrenals. Sounds like you could do with adrenal / thyroid testing to see if you need to support them. Low adrenals and / or thyroid will make you anxious and give you palpitations.

Best

Nicola