What causes sudden drop from normal TSH levels?

[cebs15]

I am a 19 year old woman with previously normal TSH levels. I get my blood work done every year, and every year the results have come back normal until now.

The first two tests were done by Quest Diagnostics for my primary physician, and the last two by LabCorp for my OB/GYN because he was diagnosing my irregular menstrual cycle. It turns out I may have Polycystic Ovarian Syndrome (PCOS), but I am otherwise very healthy.

July 19, 2008: TSH 0.63 mIU/L
May 02, 2009: TSH 0.73 mIU/L
July 21, 2009: TSH 0.014 uIU/mL
Aug 25, 2009: TSH <0.005 uIU/mL, Thyroxine (T4) 12.7 ug/dL, Triiodothyronine (T3) 215 ng/dL

The only symptoms I have that fit hyperthyroidism are intolerance to heat, excess sweating, and irregular period.

Why was my TSH level normal in May when I have always had these symptoms? And why is my TSH level dropping so rapidly now?

[Barb135]

I agree with Sally - looks like you are developing hyperthyroidism.  Were the T4 and T3 total or Free?  You need to have the Free's because the totals don't really tell you much of anything.  The Free's are what's actually available for your body to use....

Also, what are the reference ranges for the T4 and T3 - labs use different ranges depending on the method of testing....

Changes can take place very quickly with thyroid issues.....and yes, your symptoms fit. Is your doctor planning to begin treatment?  

[Super_sally888]

Looks like you are developing hyperthyroid.  yes, these things change over time. Also your symptoms sound like hyperthyroid as well.

i would think that you would need treatment.  

What has your doctor said about treatment?  Will he refer you to an endocrinologist?

[6hashi]

I am not an expert with tsh units ,but the units of july-may tests are different from those of july-aug !!!!