underactive thyroid
"I have been taking Levothyroxine for 7 years, after being diagnosed in March 2010.  I do have to take a particular brand of it though as the other brand give me a severe headache but luckily my pharmacist has my brand on his computer and that is the only one I am given.  I am now on 150mcg and I have been constant on that dose for the last 2 years.  My energy levels do plummet during the afternoon but my 'normal' thyroid colleagues do too!"