Clinical trial - using body weight to adjust t4 versus t4 + t3 dose

[vocalEK]

academic.oup.com/jcem/artic...

Link above is to full text

Thyroid Hormone Replacement for Central Hypothyroidism: A Randomized Controlled Trial Comparing Two Doses of Thyroxine (T4) with a Combination of T4 and Triiodothyronine

Abstract

Background: Dosage of T4 in central hypothyroidism is primarily guided by the free serum T4 level (fT4). However, the optimum fT4 range is ill defined, and subtle hypothyroidism might be missed using this approach.

Objectives: Our aim was to investigate the effects of a body weight (bw)-adapted T4 treatment, alone or in combination with T3, on metabolism, well-being, and cognitive function in comparison to a regimen leading to normal fT4.

Design: This was a placebo-controlled trial (double-blind, crossover).

Patients: A total of 29 patients (age 52 ± 2 yr; females/males, 8/21) with hypopituitarism, including TSH deficiency, participated in the study.

Interventions: Three regimens were compared (5 wk each): “EMPIRICAL-T4,” empirical T4 dosage (1 ± 0.05 μg/kg bw) leading to normal fT4; BW-ADAPTED-T4 (1.6 μg/kg bw T4); and “BW-ADAPTED-T3T4,” bw-adapted combination of T3 and T4 (ratio of 1:10).

Results: BW-ADAPTED-T4 administration increased mean fT4 concentrations to the upper limit of the normal range (peak levels). Compared with EMPIRICAL-T4, BW-ADAPTED-T4 treatment resulted in a lower body mass index (BMI) (29.0 ± 0.7 vs. 29.5 ± 0.7 kg/m2; P < 0.03), lower total cholesterol (198 ± 9 vs. 226 ± 7 mg/dl; P < 0.01), and lower low-density lipoprotein (LDL) cholesterol (116 ± 5 vs. 135 ± 7 mg/dl; P < 0.01). BW-ADAPTED-T3T4 treatment was associated with additional beneficial effects on ankle reflex time and working memory but resulted in supraphysiological free serum T3 (fT3) levels.

Limitations: Long-term side effects may have been missed.

Conclusions: Using a dose of 1.6 μg/kg bw improved markers commonly associated with central hypothyroidism. This suggests that T4 dosage based on bw and aiming at fT4 in the upper reference range is superior to titration of T4 aiming at middle normal fT4 concentrations in those patients.

[Aurealis]

Thanks for posting, I wish I’d known about this before. Will be useful to others I think.

[SlowDragon Administrator]

Very useful...as far higher percentage of hypothyroid patients have sluggish TSH than most medics realise

At least recent publication of new UK NICE guidelines are also recognising that dosing at 1.6mcg per kilo has merit

Useful link to persuade GP to increase dose inline with your weight

[helvella Administrator in reply to SlowDragon]

But have you seen any evidence about how that weight is constituted? E.g. fat, muscle, etc.

[vocalEK in reply to helvella]

But think how convenient that might be for the patient! Want a dose increase? Just pig-out for a month or two.

[helvella Administrator in reply to vocalEK]

Weights in your pockets?

[vocalEK in reply to helvella]

LOL!

[Angel_of_the_North]

That would under dose me as I'm only little and no way would my FT4 be high in range. So which takes precedence: dose by weight or FT4 level?

[vocalEK in reply to Angel_of_the_North]

Frankly I'd rather see guidelines that advise dosing to get FT4 into top half of range and FT3 into top quarter of range. Of course the FT3 goal might be unattainable using only Levothyroxine.

[helvella Administrator in reply to Angel_of_the_North]

From a GP's point of view, weight is surely going to win. Almost cost-free compared with doing a test (phlebotomy, lab, another appointment).

[SlowDragon Administrator in reply to helvella]

We see hundreds on here left on just 75mcg .....unless all these patients are under 9stone the weight guidelines might help them get dose increase if they have hypothyroid symptoms (regardless of TSH)

[Geetal]

Very many thanks for all your posts. It will take me some time to work through all the papers youve posted, but I shall.

Compared with other papers the paper by Zulewski on thyroid 1997 is not old. I have been in correspondence with Abbotts about the instructions on the bottle of Synthyroid about not taking walnuts. I asked did they have any published papers justifying that comment. They kindly sent me a 1970 paper. I wrote back some time ago and also wrote again asking for a response asking if they had any other justification and gave them some questions concerning the papers applicability to humans as it seemed unlikely to me that any human no mater how much they love walnuts would consume half their diet on walnuts. I am still waiting for a response from them.

[vocalEK in reply to Geetal]

You gave me a giggle there. In addition, as long as you are taking your medication on an empty stomach and not eating until an hour later, I can't see how anything in your diet would interfere with absorption.