hair loss

[memph]

i am 55yr old female, going thro menopause and i have a few bald patches on my head.the biggest is about the size of 50p. i have quite thick hair and its not thinning its just these patches.they're not red or sore but very itchy, ive been checked for lice and things but there's nothing there. i sweat alot thro my head at night but have done for quite a few months now and not noticed this before. im not on any medication. any ideas anyone?