Low TSH but also low T4 (thyroid)

[QsGal]

I’m hoping there are some thyroid experts out there who can help. For the last few years I’ve had borderline low TSH but normal/low T4 levels. I have symptoms such as heavy periods, tinnitus, brittle nails, hair loss, brain fog, tiredness and most recently bad anxiety.

My latest results are TSH 0.17 (normal range 0.3-5.5) but my T4 is 13.4 (not sure of the range but I think she said the lowest parameter ways 12 something).

The doctor explained it’s a seesaw and doesn’t really make sense. Has anyone got any experience of this or is it a case of just being normal for me? She’s asking the endocrinologist for advice but just wondered if anyone had any experience.

Low TSH and low in range FT4 suggests secondary hypothyroidism to me, ie your thyroid hormones are low (hence your symptoms), but your pituitary is not sending the right message (TSH) to your thyroid to make more T4.

Guidelines says your GP should be referring you to an endocrinologist. Might be an idea to do your homework and then go back and ask for a referral.

The treatment is the same as primary hypothyroidism, but TSH can't be used as a marker.

I thought I would update this as my journey continues in case it helps anyone else. The Dr spoke to an endocrinologist who advised to repeat the test in two months then trial meds. Unfortunately I then developed very bad anxiety and everything went out of the window and I never went back.

And to now…same symptoms as before made me return to the Dr. I had my blood tests back and now have another appointment next week to discuss . The latest results are:

TSH 0.21 miu/L (0.3-5.5)
Free T4 13.1 pmol/L (12 - 22)
Free T3 4.4 pmol/L (3.1 - 6.8)

I’ve also had the following abnormal results this time

Serum cholesterol 7.4 mmol/L
HDL cholesterol 1.93 mmol/L (0.5 - 1.7)
Non HDL 5.47 mmo/L
eGRF using creatinine 83 mL/min/1.73m2 (eGRF 60-89: CKD stage G2 if other evidence of kidney damage (proteinuria) present
Serum folate 3.7 ug/L (3.8 - 26.8)

Looking at Dr Google (I know, I know) these results could still be down to secondary hypothyroidism. I’m going to push for an endocrinologist referral and see what they say.

If anyone has any experience of this it’d be much appreciated.

Still looking like Secondary hypothyroidism to me.

The protocol states clearly that this requires a referral to an endocrinologist. If in doubt look at the NHS CKS for hypothyroidism and show this to your GP.

You are deficient in folate so you are probably deficient in another vitamins and minerals. You will need B12, iron and vitamin D testing as a minimum.

Stage 1 done! I had a follow up appointment with my GP and he brought up that potentially it’s my pituitary gland causing the issue and has referred me to an endocrinologist - I didn’t have quite the battle I thought I was going to . Actually he was refreshingly open and I really felt he listened to my concerns. I’m going to try and get it on my private health insurance as I suspect the wait for NHS would be rather long currently.

One thing he did flag though was that when the previous GP contacted the NHS endocrinologist, they advised it sounded like sub clinical hyperthyroidism rather than central hypothyroidism. Does this sound likely? It’s not really something I’ve come across in my research.

And another thank you for all those who answer; it’s been years I’ve been doubting my symptoms and bloods and even knowing that there are people out there who understand is a great comfort.

Don't let them try to pull that one!

Oh really? Is it common for them to say it’s that?

Hi there
Just wondering if you had got any further?
I've just got results back yesterday of 0.04 TSH and 9 for t4 and normal T3. Everything I look at says pituitary issue and Dr has sent letter to endo so just wondering what your journey had been? Thanks X

Hi @TheOtherHotstepper if you are still around, please could you explain what you mean by this? I have been searching MN and have almost identical blood test results as @QsGal. I have been told it might be subclinical hyperthyroidism so am very interested to know more about what you say in relation to central hypothyroidism?

And @QsGal how have you been getting on?

In the absence of @TheOtherHotstepper, can I offer you this:

Hyperthyroidism presents as low TSH with over range FT4 AND FT3. TSH is low in this case because the thyroid itself is chucking out loads of hormone.

Therefore low TSH with low in range FT4 and no more than mid-range FT3 cannot be hyperthyroidism. In this case TSH is low because pituitary is not working effectively and not promoting the thyroid to produce hormone.

The ThyroidUK forum on Health Unlocked will however explain this much better than I ever could.