Can low hormones in females cause tachycardia and weakness in legs?

Yes and No: Its challenging to relate tachycardia and weakness to hormones in women since a lot of other things may be responsible for the symptoms. There is clearly a causative link between thyroid hormones and the heart. Symptoms may also arise or fluctuate with pregnancy or monthly cycle. Based on your medications including stimulants (adderall), and history of brain injuty, you need an evaluation.