Normal tsh but high t4 post thyroidectomy? Any ideas why?

[Beckxbrown]

Near total thyroidectomy 3 years ago have reduced thyroxine now to 75mcg a day but now have high t4 again.

[PurpleNails Administrator]

Could you add actual results with ranges. Have you had full thyroid function?

Your FT4 could be high but if you aren’t converting well to FT3 you feel very hypothyroid. It can very very hard to tell if you are under medicated / over medicated the symptoms can feel very similar.

[Beckxbrown in reply to PurpleNails]

Thanks for reply, only a bit over have hopefully included results.

Results

[PurpleNails Administrator in reply to Beckxbrown]

Can’t establish much using TSH results alone. Do you have FT4 results & was FT3 tested?

[pennyannie]

Hey there again ;

A TSH blood test used in isolation to treat people taking any form of thyroid hormone replacement is the least reliable measure.

The TSH was originally introduced as a diagnostic tool to help identify a person suffering with hypothyroidism and it was never intended to be used to treat the patient when taking any form of thyroid hormone replacement.

Though I fully understand this may be all you will get tested in the yearly thyroid function test in primary care.

It is essential that you are dosed and monitored on your T3 and T4 blood tests results and this is especially true, since you have Graves and had a thyroidectomy .

A TSH is meaningless as your feedback loop on which this is based, the HPT axis - your - Hypothalamus - Pituitary - Thyroid loop is incomplete and broken as your " T " in thyroid isn't there any longer.

[SlowDragon Administrator]

Just testing TSH and Ft4 is completely inadequate

Bloods should be retested 6-8 weeks after each dose change or brand change in levothyroxine

For full Thyroid evaluation you need TSH, FT4 and FT3 tested.

Poor conversion of Ft4 to Ft3 will result in high Ft4

Very important to test vitamin D, folate, ferritin and B12

Low vitamin levels are extremely common, especially after dose reduction

Low vitamin levels tend to result in poor conversion of Ft4 to Ft3

Low vitamin levels common as we get older too

Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water and last dose levothyroxine 24 hours before test

This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip)

Private tests are available as NHS currently rarely tests Ft3 or all relevant vitamins

List of private testing options

thyroiduk.org/getting-a-dia...

Medichecks Thyroid plus antibodies and vitamins

medichecks.com/products/adv...

Blue Horizon Thyroid Premium Gold includes antibodies, cortisol and vitamins by DIY fingerprick test

bluehorizonbloodtests.co.uk...

guidelines on dose levothyroxine by weight

NICE guidelines on full replacement dose

nice.org.uk/guidance/ng145/...

1.3.6

Consider starting levothyroxine at a dosage of 1.6 micrograms per kilogram of body weight per day (rounded to the nearest 25 micrograms) for adults under 65 with primary hypothyroidism and no history of cardiovascular disease.

Also here

cks.nice.org.uk/topics/hypo...

gp-update.co.uk/Latest-Upda...

Traditionally we have tended to start patients on a low dose of levothyroxine and titrate it up over a period of months. RCT evidence suggests that for the majority of patients this is not necessary and may waste resources.

For patients aged >60y or with ischaemic heart disease, start levothyroxine at 25–50μg daily and titrate up every 3 to 6 weeks as tolerated.

For ALL other patients start at full replacement dose. For most this will equate to 1.6 μg/kg/day (approximately 100μg for a 60kg woman and 125μg for a 75kg man).

BMJ also clear on dose required

bmj.com/content/368/bmj.m41

bestpractice.bmj.com/topics...