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A member asked:

What could cause low t4 with normal tsh and t3 (liothyronine)? have tested low twice now. also currently being tested for cushing's.

3 doctors weighed in across 2 answers

Thyroid: Hard to accept a low T4 with the others normal. Please verify this with your doctor. Why are you being tested for Cushing's. Please let me know.

Answered 2/22/2016

1.6k views

Thank
Dr. David Lipkin answered

Specializes in Internal Medicine

See answer: To be accurate the T4 measurement should be Free Thyroxine. If that is low with normal TSH it can be due to "Central" Hypothyroidism: something affecting the hypothalamus or pituitary. Pituitary adenomas are the most common cause. In this case the TSH is biologically inactive.

Dr Feola agreed

Answered 2/23/2016

1.6k views

Thank

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