I think that different glands get more of the right chemicals they need to work on some days, and they up-regulate... and some days stress or nutrition causes one part of the endocrine system to crash and it has a chain reaction like effect.
my 'tingling' symptoms I unscientifically attribute to hypothyroidism. I say this because after adding thyroid support at the proper time, they went away.
I had great success following a Dr. Lam style protocol and a low-medium carb diet as described in The Schwarzbein Principle II.