Secondary hyppothyroidism

[molls57]

Hi. I'm 51, and gave birth to my 4th child nearly 10 years ago. I was diagnosed as having hypertension at my 6-week post-natal check and having been taking enelapril and bendroflumethiazide for this ever since. Prior to this, I had been perfectly healthy. 6 months later I noticed a nodule in my thyroid gland. TFTs revealed a significantly low T4 (I think it was around 60 when the normal range at the time was 80 - 120) and an unrecordable TSH ?<0.004. I was told that the hypothyroidism was secondary to a viral illness (I don't remember having suffered one) and was started on thyroxine. My T4 is now in the middle of the normal range, but throughout this time, my TSH has never altered. If this all was secondary to a viral infection, could I not have expected my TSH to show some increase as a sign of recovery? Would it be a reasonable idea to stop the thyroxine and see if things revert to normal if this is the case? The only other investigation that I have had other than the blood tests, is an USS which showed other smaller nodules in my thyroid. Should I have had an  MRI? I'd appreciate your thoughts and advice. Thanks.

[Mark Lupo, M.D.]

The other option is a secondary hypothyroidism -- again, T3 would be helpful as well as another pituitary test such as prolactin -- if these point towards a pituitary problem, then MRI of the pituitary would be appropriate.

[Mark Lupo, M.D.]

Low TSH and low T4 combo is not a viral related thyroiditis.  An undectable TSH needs further evaluation -- a T3 level would be helpful to see if this is T3 toxicosis.  I am concerned you may be hyperthyroid and adding to the problem with taking thyrxoine.

Ultrasound is more sensitive for thyroid nodules than MRI.