U.S. doctors online nowAsk doctors free
Cincinnati, OH
A 28-year-old male asked:

What would cause a low t3 (liothyronine) level but normal tsh and t4 levels? would that be considered hypothyroidism?

2 doctor answers2 doctors weighed in
Dr. Terri Washington
Endocrinology 17 years experience
No: Low t3 (liothyronine) with nl TSH and T4 is not hypothyroidism. Many things can make t3 (liothyronine) levels decrease such as illness, stress, colds etc. It is nonspecific and could also be lab error so low t3 (liothyronine) in the face of nl TSH and free T4 levels does not mean very much.
Dr. Robin Merlino
Internal Medicine 42 years experience
Birth control pills: If your TSH is normal you are not hypothyroid. T4 is converted to t3 (liothyronine) in your cells. The blood test measures t3 (liothyronine) that is bound to a protein in your blood and the active form of t3 (liothyronine). If you have too much or too little of the protein it can change the value of t3 (liothyronine). Birth control pills as well as other meds can effect the value.

Similar questions

A 21-year-old male asked:

I have hypothyroidism so can you explain to me in detail why my T3 (liothyronine) is normal while my T4 and TSH are low?

2 doctor answers4 doctors weighed in
Dr. Phillip Sirota
Internal Medicine 24 years experience
Free T4 best test: T3 (liothyronine) + T4 is the total thyroxine level. Free T4 is the active thyroxine and the best test to determine if you are hypothyroid vs hyperthyroid at any point in time. Tsh is a marker but takes several weeks to adjust to new thyroid levels. Tsh should be the only test used to guide dosage of levothyroxine in most patients.
Last updated Jan 15, 2015


Content on HealthTap (including answers) should not be used for medical advice, diagnosis, or treatment, and interactions on HealthTap do not create a doctor-patient relationship. Never disregard or delay professional medical advice in person because of anything on HealthTap. Call your doctor or 911 if you think you may have a medical emergency.