Underactive thyroid don,t understand about levels etc

[hellraiser]

Hi
I have recently been diagnosed with this but honestly do not understand what all the different terms such as tsh t3 t4 mean and what level they should be.

Are there any knowledgable people on here who can tell me what t3 and t4 is and what a normal level is.
Also what is tsh and what should that be.

Hiye, here's a link explaining it a bit www.patient.co.uk/showdoc/23068762/
What is normal differs from lab to lab so most results come with 'normal' values for that lab. Of the top of my head TSH normal is about 0.5-5 and T4 10-22 or something like that.
Also NHS direct www.nhsdirect.nhs.uk/articles/article.aspx?articleId=206

Sorry
TSH=thyroid stimulating hormone (the chemical that the brain produces to make the thyroid gland work)
T4 & T3= thyroxine (the chemical that the thyroid gland produces and that you lack in underactive thyroid)