Thyroid hormone uptake and gastric pH

[diogenes]

This is an abstract of a poster in the new ATA Conference to be held later this year. It relates gastric pH to thyroid hormone uptake in humans.

GASTRIC PH AND ORAL THYROXINE REQUIREMENT: THE IN VIVO STUDY

C. Virili1, G. Bruno2, M. Santaguida1, B. Porowska3, C. De Vito4, C. Severi2, M. Centanni1

1Medico-Surgical Sciences and Biotechnologies, “Sapienza” University of Rome, Latina, Italy

2Department of Internal Medicine and Medical Specialties, “Sapienza” University of Rome, Rome, Italy

3Department of Cardio-Thoracic-Vascular Surgery and Organ Transplantation, “Sapienza” University of Rome, Roma, Italy

4Department of Public Health and Infectious Diseases, “Sapienza” University of Rome, Rome, Italy

An increased need for thyroxine has been observed in patients with H pylori related gastritis and gastric atrophy, disorders that may impair gastric acid secretion. In vitro evidence supports the notion that the variations of gastric pH may also interfere with T4 dissolution profile. This study was, therefore, designed to obtain the in vivo evidence of a direct correlation between the therapeutic dose of T4 and the gastric pH, directly measured during endoscopy. A total of 43 T4-treated hypothyroid patients (36W/7M; median age = 51yrs) have pledged to take thyroxine in fasting conditions, abstaining from eating or drinking for one hour. All patients underwent endoscopy with multiple biopsy specimens while gastric juice was collected for pH evaluation. To calculate the excess of T4 required in each patient, the individual dose of T4 was compared to the one observed in age- and BMI-matched patients but without gastrointestinal and/or pharmacological interference. The results were plotted against the actual pH and the H+ concentration titrated with NaOH-. To obtain a similar serum TSH (median = 1.11mU/l), the dose of thyroxine was progressively higher along with the increase of the gastric pH (r2 = 0.1209; p< 0.0223) and the actual H+ concentration (r2 = 0.1275;p< 0.0219). A multivariate analysis revealed that pH act as an independent variable in determining the dose of T4 (p < 0.029). Also, the excess of T4 dose (ED) required, plotted with gastric acidity in each patient, was highly correlated with the increased pH (p < 0.001) and decreased H+ concentration (p < 0.0001). Based on their pH, patients were then subdivided in two groups using as cut-off the median pH of the whole sample (2.4; IQ1-3 = 1.5-6.1). Only 6 out of 24 patients (25%) in group A (median pH = 1.52) needed a high T4 dose vs 17 out of 19 (89%;p<0.0001) in group B (median pH = 6.47). Overall, the median T4 dose was increased by 15% in group A and by 48% in group B. The ED of T4 was also differently distributed in patients with atrophic gastritis (90%), with pangastritis (73%) and with antritis (40%). This is the first in vivo study showing a positive correlation between gastric pH and the need for thyroxine in humans.

[helvella Administrator Thyroid UK]

diogenes,

Thank you.

For years this has appeared to be, bluntly, bleeding obvious. Not knocking the researchers - for sometimes the bleeding obvious isn't what actually happens. It is highly appreciated that they have done the work and are publishing.

So we have this wonderful situation in which hypothyroid patients, with impaired stomach acidity, have to take a medicine which is less well absorbed. Compounded by them so often being prescribed PPIs, H2 blockers, etc., due to incorrect diagnosis and treatment. Which will only further impair absorption.

Totally ludicrous that it has taken ninety years from first synthesis, or almost seventy years from launch by Glaxo, for this to be tested. Especially against a background of patients insisting that this is the case - and doing things like taking with lemon juice.

[JGBH]

Thank you Diogenes.

I have taken PPIs for over 2 decades... and have GERDS and reactive gastritis. I have been on Levothyroxine since 1980, post thyroidectomy. Have been feeling very unwell for the past 3 years. Simply cannot function at all.

In view of this article how should I take my thyroid medication? Would it be safe to take it with lemon juice (taking into consideration I have gastritis and GERDS)? Or should my Levo dose be increased?

Thank you if you feel able to reply.

[diogenes Remembering in reply to JGBH]

By whatever means, try to get your stomach acid stronger if only for a while. Can you have alternate days of taking PPIs and every day taking T4. That way at least you'll have one day of good uptake. Otherwise you need one and a half times more T4 than you would take if not on PPI. This means of course that your blood thyroid parameters (TSH, FT4, BUT NOT FT3) would be meaningless. In your case then only FT3 would mean anything.

[JGBH in reply to diogenes]

Diogenes

Thank you for your valued advice. I do sometimes forget to take the PPI... but will try to do so on alternate days for a while. The trouble is with the reflux of course. It feels a bit like finding oneself between the devil and the big blue sea! Nothing is ever simple.

Also, I wonder if you would be able to tell me whether I should have been prescribed T3 post thyroidectomy rather than Levothyroxine? (I had papillary adenocarcinoma in 1980), and whether an NHS endo should still prescribe T3 because I had a form of thyroid cancer in the first place? My GP is insisting that an NHS endo will not prescribe T3... and she certainly won't, well can't apparently. Thanks again if you feel able to reply.

[Hidden]

I have no gut problems at all but I still test my PH every month. I have a normal reading. It is a cheap and easy way to test with litmus strips. People with an abnormal test can easily adjust their diet to help.

[ITYFIALMCTT in reply to Hidden]

The pH in the study is the gastric pH which requires extraction of samples during an endoscopy.

Are you using litmus to test the pH of your mouth?

[diogenes Remembering in reply to ITYFIALMCTT]

The whole extraction is done direct from the stomach by a swallowed tube.

[Hidden in reply to ITYFIALMCTT]

I understood what it was i.e. gastric. I use the test on my urine only. It still gives a good idea of the PH of the body in general.

[diogenes Remembering in reply to Hidden]

I'm afraid I have to disabuse you of the value of urine pH. In a famous experiment Prof J S Haldane swallowed a good deal of hydrochloric acid to discover if it had any effect on the pH of his urine. It didn't change his urine pH at all but merely made his teeth fizz. What is really important in urine is protein content - ie frothiness. Too much indicates renal problems.

[diogenes Remembering in reply to diogenes]

Perhaps I was a little facetious here, but the message is that a lot of drugs can interfere with urinary pH and give false indications, and on the other hand things you think might have an effect, don't. It's important to check that no interfering substances are being taken, if the result is to be meaningful.

[Hidden in reply to diogenes]

Yes I agree