Monday, April 30, 2012

Metformin ( glucophage) effects Thyroid test

Diabetes ,  Metformin  effects Thyroid Test

Definitions :
Low thyroid  (hypothyroidism ) from various causes is diagnosed from symptoms and confirmed by laboratory test   The TSH ( Thyroid stimulating Hormone ) test is usually elevated
and the  T4 ( thyroid hormone ) level is decreased.

Subclinical hypothyroidism  ( someone with no symptoms are physical findings of hypothyroidism with an elevated TSH and low T4 )

Metformin effect
Metformin has an effect on TSH  and T4 levels in people with hypothyroidism.  Metformin decreases  TSH levels and may increase T4 levels making it more difficult to diagnosis and monitor treatment of hypothyroidism.

Complicates Thyroid replacement therapy
 Doctors follow TSH levels and adjust thyroid hormone replacement therapy to correct the TSH into the normal range. Metformin may complicate this process by making the TSH level appear lower than it is .
The mechanism of this effect is not known but one theory suggest that metformin may increase the absorption of thyroid hormone from the intestinal tract making a lower replacement dose adequate. This is an interesting unconfirmed idea .  Finding the correct replacement dose for someone on metformin will require some thought by your physician.

Complicates the diagnosis of subclinical hypothyroidism
The effects of Metformin on  lowering TSH  may  also interfere with the diagnosis of subclinical hypothyroidism

 People with normal thyroids do not seem to be effected by metformin. 

Have fun , be smart and understand your lab test.
David calder,MD

Metformin and Vitamin B12  tomorrow

1 comment:

Your comments and questions are appreciated. David Calder,MD