Can release of hormones from fat cells cause hair loss and heart palpitations? i've lost 42 pounds, but i eat high protein and at least 1200 cals/day

Check your thyroid: You might have an over active thyroid. It might be used to having to manage the "larger" you, and now is just doing too much. Your family doc can do a simple blood test to check a tsh, t3 (liothyronine), (liothyronine) ; t4, and free T4 ; free t3 (liothyronine). That is a good place to start! also, a basic ekg/ecg can investigate the palpitations to make sure they don't need additional work up, like an echo. Congrats on weight loss!