Thank you Olena but i want to know the condition when TSH level is normal but only FT3 and Ft4 level is abnormal in clinical laboratory. 

Hi Mahesh, 

A patient with normal serum TSH but elevated serum FT4 and FT3 may have:

1) Central hyperthyroidism 

2) Thyroidal resistant syndrome 

On the other hand, a patient with normal serum TSH but low serum FT4 and FT3 have:

1) Central hypothyroidism 

2) during the treatment of any hyperthyroid condition 

As you know, there are different causes and subtypes of the above mentioned conditions. In addition, there are other causes but they are very rare.

With all my special respect to Olena, serum TSH is suppressed rather than normal in conditions number 3, 4 and 5 of her response. 

I hope this is helpful.

This paper may be useful for you.

Don't forget interferences! Heterophilic antibodies, THAAb or Anti-ruthenium antibodies (Roche platforms).

I think it has already been well answered.End organ resistance and lab error are the things that first come to my mind

Thanks to all 

There may be a defect in the composition of the elements that feedback between TSH and T4,T3