Thursday, October 30, 2008

Thyroid Hormone Interference

Coffee has been added to the list of things that interfere with absorption of thyroid hormone. That's the list of things that you shouldn’t take along with thyroid hormone keeps growing. 


Coffee isn’t the first thing discovered to interfere with thyroid hormone. Back in 1992 both aluminum hydroxide antacids and the iron supplement ferrous sulfate were reported to interfere.  In 2000, a report in JAMA added calcium carbonate to the list. Soy protein shakes were added in 2001. The drug Raloxifene was added in 2003.  Then chromium picolinate in 2007. And now, coffee.

Most simply hinder absorption of the drug from the digestive tract and effectively reduce the dose that gets into your blood. The problem shows up with food or other medications that people will start to take regularly. This can throw of your dose requirements.

Tired people drink coffee. According to a paper published this March, coffee decreased the amount of thyroid hormone absorption by about a third. Instead of tired, these people will start to feel exhausted. So, they drink more coffee and they absorb even less of their hormone dose. It’s a vicious cycle. The trick is to take thyroid hormone first thing in the morning on an empty stomach, at least 30 minutes before eating anything. 

Coffee isn’t the first thing discovered to interfere with thyroid hormone. Back in 1992 both hydroxide antacids and the iron supplement ferrous sulfate were reported to interfere. In 2000 a report in JAMA added Calcium carbonate to the list. And soy protein shakes in 2001. And the drug Raloxifene was added in 2003. Then chromium picolinate in 2007. And now, coffee.

There are some foods, namely cabbage that are well known to decrease thyroid hormone production and cause goiters if eaten in large enough quantities.

Thus the general direction given to all patients taking supplemental thyroid hormone to always take it alone without food or other medication. You just don’t know what’s going to mess things up.

When a patient who is taking thyroid hormone does well initially and then it seems the drug stops working, the first thing to rule out is interference from something else they are taking.

A 2007 paper tells us that taking thyroid hormone at bedtime works much better than taking it in the morning. For some reason the hormone is better absorbed at night and reaches greater blood concentrations than when taken in the morning. 


References:

Thyroid. 2008 Mar;18(3):293-301. 
Altered intestinal absorption of L-thyroxine caused by coffee.
Benvenga S, Bartolone L, Pappalardo MA, Russo A, Lapa D, Giorgianni G, Saraceno G, Trimarchi F.

Arch Intern Med. 1992 Jan;152(1):183-4.Links
Evidence for interference with the intestinal absorption of levothyroxine sodium by aluminum hydroxide.
Sperber AD, Liel Y.

Ann Intern Med. 1992 Dec 15;117(12):1010-3.Links
Ferrous sulfate reduces thyroxine efficacy in patients with hypothyroidism.
Campbell NR, Hasinoff BB, Stalts H, Rao B, Wong NC.

JAMA. 2000 Jun 7;283(21):2822-5. 
Effect of calcium carbonate on the absorption of levothyroxine.
Singh N, Singh PN, Hershman JM.

docr Pract. 2001 May-Jun;7(3):193-4. 
Use of soy protein supplement and resultant need for increased dose of levothyroxine.
Bell DS, Ovalle F.

Arch Intern Med. 2003 Jun 9;163(11):1367-70. 
Raloxifene causing malabsorption of levothyroxine.
Siraj ES, Gupta MK, Reddy SS.

Thyroid. 2007 Aug;17(8):763-5. 
New medications which decrease levothyroxine absorption.
John-Kalarickal J, Pearlman G, Carlson HE.

Presse Med. 2007 Oct;36(10 Pt 1):1390-4. Epub 2007 Apr 18. 
[L-thyroxine pseudomalabsorption: a factitious disease]
Molines L, et al.

Clin Endocrinol (Oxf). 2007 Jan;66(1):43-8. 
Effects of evening vs morning thyroxine ingestion on serum thyroid hormone profiles in hypothyroid patients.
Bolk N, Visser TJ, Kalsbeek A, van Domburg RT, Berghout A.



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