Diabetes , Metformin effects Thyroid Test
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 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.
Metformin and Vitamin B12 tomorrow