Hi. I've recently been posting on PAS forum but on examining my recent blood tests I noticed a difference in thyroid function results. I have tried researching but am baffled. My GP has tested TSH and Free T4 many times since 2012 with results as follows

TSH

2012 1.23mu/L (0.2 - 4.5mu/L)

2013 1.66mu/L (0.20 - 4.50mu/L)

2013 1.35mu/L (0.20 - 4.50mu/L)

2014 1.06mu/L (0.20 - 4.50mu/L)

2015 1.77mu/L (0.20 - 4.50mu/L)

2016 1.87mu/L (0.20 - 4.50mu/L)

2017 2.10mu/L (0.20 - 4.50mu/L)

Jan 2018 1.99mu/L (0.20 - 4.50mu/L)

20th Sept 2018 2.32mu/L (0.20 - 4.50mu/L)

Free T4

2012 14.3 pmol/L (9 - 23 pmol/L)

2013 16.0 pmol/L (9 - 23)

2013 14.9 pmol/L (9 - 23)

2014 14.5 pmol/L (9 - 23)

2015 14.9 pmol/L (9 - 23)

2016 10.7 pmol/L (7.0 - 17.0 pmol/L)

2017 12.3 pmol/L (7.0 - 17.0)

Jan 2018 11.8 pmol/L (7.0 - 17.0)

20th September 2018 10.3 pmol/L (7.0 - 17.0)

This all seems fairly normal to me however my recent Medichecks thyroid results (26th September) are as follows:-

Thyroid Stimulating hormone 3.34 mIU/L (0.27 - 4.20)

Free Thyroxine 19.300 pmol/L (12.00 - 22.00)

It would seem that even though bloods taken by GP and Medichecks were only six days apart there seems to be a big increase in TSH and Free Thyroxine. Can anyone shed any light on why this could be?